NATL INST OF STAND & TECH

A111D7 DBHflMfl

NiST

PUBLICATIONS

J- iiJ Physics Laboratory

SUPPORTING U.S. INDUSTRY,

GOVERNMENT AND THE

SCIENTIFIC COMMUNITY BY

PROVIDING MEASUREMENT

SERVICES AND RESEARCH.

FOR ELECTRONIC, OPTICAL,

AND RADIATION TECHNOLOGY
Physics Laboratory at a Glance

Director's IVlessage 2

Electron and Optical Physics Division

Atomic Physics Division 12

Optical Technology Division.,

Ionizing Radiation Division 28

Time and Frequency Division 36

Quantum Physics Division... 44

Office of Electronic Commerce in

Scientific and Engineering Data 52

Awards and Honors 54

Organizational Chart 63

Physics Laboratory Resources.. 64
PHYSICS LABORATORY AT A GLANCE

1

PL Vision

Preeminent performance in measurement

science, technology, and services.

PL Mission

The mission of the NIST Physics Laboratory is to support U.S. industry, govern- ment, and the scientific community by

providing measurement services and re- search for electronic, optical, and radiation technology. The Laboratory provides the foundation for metrology of optical and

ionizing radiation, time and frequency,

and fundamental quantum processes.

PL Divisions

Physics Laboratory is organized into six divisions that are vertically integrated, with

projects ranging from basic and applied

research to measurement services. Division

scientists collaborate with one another,

with other organizations within NIST,

and with partners outside of NIST in interdisciplinary activities related to health

care quality assurance, nanotechnology,

homeland security, defense preparedness,

information technology, and environmental and energy applications.

Electron and Optical Physics Division:

to support emerging electronic, optical,

and nanoscale technologies.

Atomic Physics Division: to determine

atomic properties and investigate

fundamental quantum interactions.

Optical Technology Division: to provide

the foundation for optical radiation measurements for our Nation.

Ionizing Radiation Division: to provide

the foundation of ionizing radiation measurements for our Nation.

Time and Frequency Division: to provide

the foundation of frequency measurements and civil timekeeping for our Nation.

Quantum Physics Division: to make

transformational advances at the frontiers of science, in partnership with the University of Colorado at JILA.

Office of Electronic Commerce in Scientific and Engineering Data: to coordinate and facilitate the electronic dissemination of information via the

Internet.

PL Resources

1 85 full-time staff (1 52 scientific]

with expertise in:

• Atomic, molecular, and optical

physics

• Computational physics

• Condensed matter physics

• Health physics

• Medical physics

• Nuclear physics

• Biophysics

• Chemistry

• Metrology and precision measurement

$75 million annual budget

Unique facilities, including:

• Bidirectional Optical Scattering

Facility

• Center for High-Accuracy

Retroreflection Measurements (CHARM)

• Electron Beam Ion Trap (EBIT)

• Electron Paramagnetic Resonance

Facility

• EUV Optics Fabrication and

Characterization Facility

• High-Illuminance Standards and

Calibration Facility

• High-Resolution UV and Optical

Spectroscopy Facility

• W.M. Keck Optical Measurement

Laboratory

• Low-Background Infrared Radiation

Facility (LBIR)

• Magnetic Microstructure

Measurement Facility

• Mammographic X-Ray Instrument

Calibration Range

• Medical-Industrial Radiation Facility

(MIRF)

• Neutron Imaging Facility

• Neutron Interferometer and Optics

Facility (NIOF)

• Primary Optical Watt Radiometer

(POWR)

• Radiation Detector Test Facility

• Radiopharmaceutical Standardization Laboratory

• Spectral Irradiance and Radiance

Calibrations with Uniform Sources

Facility (SIRCUS)

• Synchrotron Ultraviolet Radiation

Facility (SURF III)

Standard time dissemination services:

• Radio stations WW, WWVH, and

WWVB

• Automated Computer Time Service (ACTS)

• Internet Time Service (ITS)

• Time Measurement and Analysis

Service (TMAS)

Measurement and calibration services

for:

• Color and color temperature

• Dosimetry of x rays, gamma rays, and

charged particles

• Neutron sources and neutron

dosimetry

• Optical properties of materials

• Optical wavelength

• Oscillator frequency

• Phase and amplitude noise

• Photodiode spectral responsivity

• Photometry (e.g., luminous intensity,

luminous flux, illuminance)

• Radiance temperature

• Radiation detectors

• Radioactivity sources

• Spectral radiance and irradiance

• Spectral transmittance and reflectance

PL Website

http://physics.nist.gov/
© Sam Kittner/ Kittner.com Director's Message

This report is intended to provide not only an overview of the NIST Physics Laboratory's programs, but also a sense of the range, excitement, and relevance of the measure- ment science pursued in the Divisions.

In keeping with the mission of NIST, the Laboratory supports industry, govern- ment, and the scientific community with measurement research and services in

electronic, optical, and ionizing radiation technologies. Our great strength—and

what distinguishes us from an academic or

industrial laboratory—is that we are vertically integrated with a balanced portfolio of programs that span the full range from

those that address the immediate needs of industry to the more fundamental

research that anticipates the future needs of industry, government, and the scientific community.

The Laboratory addresses the fundamental

triad of standards, measurements, and data

in a climate of vigorous and competitive

research. Just as the breadth, vigor, and ex- cellence of our research programs provide

credibility for our services, so the increas- ing demands for our services provide a strong and crucial focus for our research programs. The Physics Laboratory has

ably demonstrated that mission-oriented

research can be just as challenging,

cteative, and significant as "curiosity

driven," academic research.

For example, our Time and Frequency

Division's seven different T&F services are supported by major efforts in the development of optical frequency standards, chipscale atomic clocks, and next-generation

cesium fountain atomic clocks, which ate

in turn supported by fundamental research on trapped ions and neutral atoms. And

just as our work on trapped ion clocks led

to our program in quantum information,

so our ability to make quantum logic gates

led to the development of the quantum

logic clock. Similarly, the Optical Technology Division's work on next-generation

light detectors led to the creation of single

pairs of photons on demand, which is now

an integral part of our program on quan- tum information. Likewise, the Ionizing

Radiation Division is developing highly

sensitive neutron detectors for homeland

security at the same time that it is using

ultracold neutrons to investigate symmetries and parameters of the nuclear weak

interaction.

Among our many responsibilities is the maintenance of the U.S. national stan- dards for the Systeme International (SI)

base units of time (the second), light (the candela), and noncontact thermometry

(the kelvin, especially above 1200 K). We

provide the basis for such SI derived units

as the hertz (frequency) , the becquerel (radioactivity), and the optical watt and the lumen (light output). At the same time,

scientists in the Physics Laboratory work

with industry to develop new measurement

technologies that can be applied to such

fields as communications, microelectronics, nanomagnetics, photonics, industrial radiation processing, the environment,

health care, transportation, space, energy,

security, and defense.

Our partners are many and our outreach

extensive. JILA, our joint institute with

the University of Colorado, is now in its

46"'' year and still gaining stature with three recent Nobel Laureates. Modeled loosely on JILA, our new Joint Quantum Institute

(JQI) with the University of Maryland

held its Inaugural Symposium on 27

March 2007, an event notable for its high

concentration of both talent and enthusi- asm. Following in the same footsteps, our

nascent Joint Biophysics Institute with

the University of Maryland Biotechnol- ogy Institute is even now formulating a Memorandum of Understanding. At the same time, the Physics Laboratory was

2
Director's Message 3

honored by the former NIST Director's

selection of its Electron Physics Group,

led by Robert Celotta, to form the core of

a new organizational unit, the Center for Nanoscale Science and Technology.

The Laboratory places great importance on

determining, and focusing on, its highest

priority programs. For optical radiation measurements, we rely heavily on the Council for Optical Radiation Measure- ments (CORM), formed to help define

pressing problems and projected national needs in radiometry and photometry. Its aim is to establish a consensus on industrial and academic requirements for physical standards, calibration services, and

interlaboratory collaborative programs in the fields of ultraviolet, visible, and infra- red measurements. Similarly, the Council on Ionizing Radiation Measurements and

Standards (CIRMS) helps to advance

and disseminate the physical standards needed for the safe and effective application of ionizing radiation, including x rays, gamma rays, and energetic particles such

as electrons, protons, and neutrons. For

time and frequency, where the constitu- ency is less well defined, we use decadal

surveys and contacts with manufacturers of

WWVB clocks and GPS receivers. When

we can assist in an important area of

measurement or research, we form

Cooperative Research and Development

Agreements with industry. Laboratory scientists serve with distinction in standards- development committees and readily give

of their time to assist the public.

Our talent is focused on meeting today's

challenges—in biosystems and health care, quantum technologies, and nanoscale

metrology, to name but a few. For health

care, the Physics Laboratory conducts

research on standards to enable hospitals

to use nuclear medicine more effectively. We develop ways to image single biomolecules and to use terahertz radiation for measuring biomolecular processes. The

Physics Laboratory is at the forefront of

the nascent field of quantum information

processing—computing and communications—challenging preconceived notions

of computational complexity and communications security. Similarly, the Physics

Laboratory has been a leading center for metrology at the nanoscale, even before "nanotechnology" gained prominence. We

pioneered electron-spin microscopy, which

images magnetic materials, and our unique

EUV optics facility supports the electronic industry in its drive to develop advanced

lithographic systems for producing ever smaller chips.

Over the years, the Physics Laboratory's contributions have been recognized by

awards from industry, government, and

the scientific community, including 3 Nobel Prizes, 5 members of the National

Academy of Sciences, 1 MacArthur Fellow,

and 47 Fellows of the American Physical

Society. Some of our recent awards and

honors are listed in this report.

As you browse this summary of the Physics

Laboratory, we expect you will want to

learn more. We invite you to visit our website, http://physics.nist.gov/, and we invite your inquiries and interest in measurement

services and collaborations.
Electron and Optical

Physics Division

GOAL

To support emerging The strategy for meeting this goal is to improve measurement science and to electronic, optical, and develop the measurements and standards needed by emerging science and

nanoscale technologies technology-intensive industries.

Thefirst strategic focus is the

development of metrology

for extreme ultraviolet (EUV) optics,

the maintenance of national primary

standards for radiometry in the EUV

and adjoining spectral regions, and

the operation of national user facilities

for EUV science and applications.

EXTREME ULTRAVIOLET

RADIATION METROLOGY

INTENDED OUTCOME AND

BACKGROUND

The intended outcomes of this program

are: maintenance and continuous improvement of the national primary measurement

standards for extreme ultraviolet radiation (EUV: wavelengths between 4 nm and

250 nm, i.e., from soft x rays to vacuum

ultraviolet), development of techniques

for fabricating and characterizing EUV

optical systems, and the development of a synchrotron-based, national primary stan- dard for source-based optical radiometry.

The Division has longstanding responsibility for the national primary radiometric

standards in the EUV region of the spec- trum. EUV radiation is an important tool

for determining the electronic structure of

materials, diagnosing plasmas, measuring

dynamics of the upper atmosphere, and

probing the structure and dynamics of

astrophysical objects.

One of the top candidates for next- generation semiconductor manufacturing

technology is an EUV micropatterning tool, since operation at this short a wavelength (13 nm vs. 193 nm for present, production ultraviolet lithography) enables

diffraction-limited imaging of features with smaller critical dimensions. We are working actively with the semiconductor

industry to develop new metrology and

testing capabilities as needs arise in their

effort to commercialize this next-generation lithography.

The Division's key tool for EUV metrol- ogy is the NIST Synchrotron Ultraviolet Radiation Facility (SURF III). SURF III, the successor to the world's first dedicated

source of synchrotron radiation, is a low- energy (< 400 MeV), high beam-current

(above 1 A), perfectly circular electron storage ring. Its operational characteristics

are ideal for EUV metrology. It does not produce the hard x-ray radiation of higher energy sources, and it can be operated over

a wide range of beam energies to match the

spectral response of systems of interest. As

a calculable source of radiation from the

far infrared through EUV spectral regions,

SURF is also used as a primary standard

for source-based radiometry throughout

the optical spectrum.
Electron and Optical Physics Division 5

ACCOMPLISHMENTS

Calibration of the EUV

Variability Experiment for

NASA's Solar Dynamics

Observatory Mission

The SURF III facility has caHbrated

every extreme ultraviolet (EUV) spec- trometer flown on NASA missions since the 1970s. In 2008, the first mission of

NASA's Living With a Star program is scheduled for launch: the Solar Dynamics Observatory (SDO). The SDO

mission will provide measurements and models of the solar radiation and

dynamics that can disturb Earth's space weather environment.

Figure 1 . The EVE package in the course of a SURF III calibration run. Here it is being loaded into a large vacuum chamber on SURF III beamline 2, which is enclosed in a clean room environment. SDO contains three instrument packages, one of which is the EUV Variability

Experiment (EVE), built by the Laboratory for Atmospheric and Space Physics

(LASP) of the University of Colorado.

EVE measures solar EUV irradiance with unprecedented spectral resolution,

temporal cadence, accuracy, and precision. The EVE investigation program

incorporates physics-based models of the

solar EUV irradiance to advance the understanding of the solar EUV irradiance

variations based on the activity of the

solar magnetic features. Such variations have been found to have major effects on

satellite drag and radio propagation in

the ionosphere, due to the complete ab- sorption of EUV radiation in the earth's upper atmosphere.

The EVE package was calibrated at SURF

III before its transfer to NASA for incorporation into SDO. Suc^h calibration is essential for integrating EVE results into the

historical record of solar EUV variability, and SURF III is presently the only facility in the world that can provide this service.

Contact: Dr. Mitchell L. Furst [301] 975-6378

mitchell.furst@nist.gov

Electron Emission Properties of

Graphene and Carbon Nanotube

Devices

Carbon nanotubes and nanosheets (gra- phene) are promising candidates for lowfield, cold-electron emission devices, such

as efficient electron sources and displays.

Low threshold fields are required to initiate electron emission in these systems, on the order of 1 mV/nm to 10 mV/nm.

This field strength is roughly the same

as that used in photoemission electron microscopy so we investigated the field- emission and photoemission properties of

carbon nanotubes and nanosheets, with

emphasis on the threshold field and the uniformity of emission. Typical nonimaging characterization focuses on the total emitted current. However, to optimize

device performance, the entire emitter

structure must be active.

This motivated our spatially resolved photoelectron emission microscopy (PEEM)

studies of prototype devices produced by

Prof Brian HoUoway at the College of

William and Maty. These studies were carried out in collaboration with Prof. Martin

Kordesch of Ohio University, while he was on sabbatical leave at NIST. Devices

prepared for photoelectron emission imaging and field emission microscopy were

observed in both imaging modes with

submicron spatial resolution.

Figure 2. [a] PEEM and [b] field-emission micrographs of a carbon nanotube electron emission device.

It was found that low-current emission was

uniform and correlated with the photoelectron (PEEM) image. Hot spots were

observed on some specimens that could be imaged simultaneously in PEEM and field emission microscopy. Metallized graphene

sheets were found to be vety good emitters,

and the nature of their emission enhancement is currently under study.

Contact: Dr. Uwe Arp

[301] 975-3233

uwe.arp@nist.gov

Record Beam Currents,

Autonomous Operation, and

Royal Visit at SURF III

In late 2006, it became possible for the first time to inject currents in excess of an ampere

into the SURF III electron storage ring. When SURF II first came on line in the mid1 970s, its maximum injection currents were

1 0 mA. These were increased to about 300 mA by the time of the conversion to SURF III in 1997, but the maximum currents then could not be generated reproducibly. A wide range of improvements in the

injection and RF control tystems, carried out

over the past five years, have led to deterministic injection conditions, which generate

initial currents that are as large as those used

in any other synchrotron radiation source.
6 NIST Physics Laboratory

SURF III Status Display

Beam Current 177.91 mA

Electron Energy

380.0 lUleV

Lifetime RFVolta^B

7-20 h 28.15 kV

Orbital radius 837.0773 mm

Ring Vacuum

6.38E-10hPa FWHMXFWHMY

3.49 mm 2.00 mm

Dose Rate

3.17 mrem/h 12B2 mAh

19:00 ,19:00

07/1 1 09/1

1

Time

16:00

12/11

Last updated: 12-Nov-2007 16:00:20 Comment: AUTO REINJECT

Figure 3. SURF III beam current as a function of time, showing re-injections during the

night in the autonomous mode of operation.

Furthermore, in 2007 we were able to institute regular autonomous operation of the

facility, whereby it automatically re-injects

itself when the beam current decays to a pre- determined target level. (Such decay occurs due to electrons being lost from the beam

due to collisions.) This allows for round-theclock operation, which has been necessary to accommodate growing user demand, particularly that associated with lifetime testing of EUV optical components, which is discussed

below.

Figure 4. HRH Princess Sumaya of Jordan

receives a certificate of proficiency in synchrotron facility operation from

Dr. Katharine Gebbie.

The synchrotron radiation research community is tight-knit, and members of the SURF III staff frequently interact with their counterparts at other synchrotron facilities worldwide, hi May 2007 an unusual engage- ment of this type occurred in the form of

a visit by a royal personage, HRH Princess Sumaya ofJordan. The Princess is the head of

the Royal Scientific Society of Jordan, which

contains the Jordanian counterpart of NIST,

and is also the sponsoring organization of

a synchrotron radiation facility, SESAME,

which is under construction there. During

her tour of SURF III, Princess Sumaya was

offered the opportunity to inject a beam, and

carried out the procedure quite successfully.

Contact; Dr. Charles W. Clark

[301] 975-3708

charles.clark@nist.gov

Predicting the Lifetime of

Extreme Ultraviolet Optics

To help the semiconductor industry meet

its goal of achieving extreme-ultraviolet lithography (EUVL) production by 2010, we have established a dedicated beamline at SURF III for durability testing of multilayer

mirrors, an essential underlying technology.

The new beamline is devoted to acceler- ated testing, and we have added a second branch to a preexisting beamline to provide

broadband illumination (wavelengths of ap- proximately 1 1 nm to 50 nm) onto a single

spot at approximately 1 00 times the intensity

attainable before.

To determine how damage scales with vari- ous parameters, we recently exposed EUVL

mirrors (provided by SEMATECH from

work it co-ftmded) to vaiying levels of light

intensity, water, and hydrocarbon concentrations. Contrary to expectations, we found

that increasing amounts of water vapor

caused less mirror damage, which may be due to a simultaneous increase in the ambient hydrocarbon levels. Subsequent experi- ments have shown that deliberately introduc- ing trace amounts of a simple hydrocarbon

like methanol can mitigate significantly the water-induced damage.

Contact: Dr. Thomas B. Lucatorto [301) 975-3734

thomas.lucatortodinist.gov

Nanoscale Chemical

Imaging with Electron Beam

Tomography

Tomography became an important field about 40 years ago with the application

of X rays to medical imaging. The practice

quickly spread to electron microscopy. The

principal contrast mechanism in x-ray scat- tering is absorption which follows Beer's Law, i.e., the rule of exponential attenuation. Although it was necessary to develop

radically different algorithms for tomography using magnetic resonance imaging

or ultrasound, the electron microscopy

community imported the assumption of a probe traveling in a straight line through a sample with exponential attenuation.

This assumption is valid for thin samples, but for thick samples multiple electron

scattering renders it invalid. Our theoretical analysis found that near the onset of

multiple scattering (as the sample thickness under consideration increases), there is a regime in which the projective assumption

remained valid, but the transmission as a function of thickness deviated significantly

from Beers Law. Extensive numerical simulations confirmed this, attaining excellent reconstructions of an 8 pm square sample

of a photonic band gap material using the multiple scattering transmission function.

Figure 5. [a] A synthetic photonic band

gap structure, and (b] its reconstruction

using Bayesian tomography in the multiple

scattering regime.

We used a Bayesian approach known as the generalized Gaussian Markov random

field, and extended it to treat systems with

multiple scattering. The principal features of this formalism are a prior distribution
Electron and Optical Physics Division 7

based on correlations of neighboring pixels

(or voxels in 3D) in which the smoothness

of the reconstruction may be adapted to

the sample, and a quadratic approximation

to the log of the likelihood derived from

Poisson statistics. In its original formulation, Beer's Law was also assumed. We

made a more general assumption: that

the transmission is any known function,

with sufficient differentiability, of a linear combination of the material parameters

of the sample. This has enabled us to

get highly satisfactory reconstructions of

three-dimensional materials structure from

limited angular sampling data.

Contact: Dr. Zachary H. Levine

(301] 975-5453

zachary.levineOnist.gov

The Division maintains two efforts in this

area, one theoretical and two experimental. The theoretical program is focused on quantitative modeling of degenerate

quantum gases, with particular attention to the dynamics of Bose-Einstein condensates

subject to external fotces, e.g., manipulation of condensates confined in an optical

lattice. This program is an outgrowth of

extensive collaborations with experimental groups at NIST, JILA, and elsewhere,

begun in the mid-1990s.

The experimental programs are concerned

with the application of light storage in and

retrieval from atomic systems as a tech- nique for quantum information processing, and the development of high-speed

quantum cryptography.

Thesecond strategic focus is

metrology for coherent matterwave and quantum information

processing devices.

COHERENT MATTERWAVE AND QUANTUM

INFORMATION

PROCESSING

METROLOGY

INTENDED GUTCGME AND

BACKGROUND

This program provides measurements and

data to enable the development of ultra- cold atom technology, in particular the use of coherent matter waves in sensors, atom

interferometers, and quantum information

processing devices.

ACCOMPLISHMENTS

Quantum Key Distribution

System Operating at a SiftedKey Rate Over 4 Mbit/s

We have collaborated with NIST's Advanced Network Technologies Division in developing a complete fiber-based, polarization-encoded quantum key distribution (QKD) system based on the Bennett-Brassard protocol (BB84). The system operates

at a clock rate of 1 .25 GHz, and is capable

of producing key bits from quantumchannel transmissions (sifted key) at rates above 4 Mbit/s over 1 km of optical fiber. This output can be processed to produce

unconditionally secure cryptographic key

for encrypting messages.

Our results represent a new record in the operational output rate of a QKD system

based on single-photon transmission. They are made possible by the integration

of quantum cryptography protocols with

classical high-speed telecommunications

techniques. The quantum channel uses 850 nm photons from attenuated highspeed vertical cavity surface-emitting lasers

(VCSELs), and the classical channel uses 1550 nm light from normal commercial

coarse wavelength division multiplexing

devices. A polarization auto-compensation

module has been developed and utilized to recover the polarization state and to compensate for temporal drift. An automatic

timing alignment device has also been

developed to quickly handle the initial configuration of quantum channels so that detection events fall into the correct timing

window. These automated functions make

the system more practical for integration

into existing optical local area networks.

We are developing a free-space optical

QKD system operating at the Balmer

alpha wavelength of 656 nm, where light

from the sun is attenuated by 7 dB in a narrow interval, which is advantageous

for daylight operation of free-space QKD

systems. We are also developing semiconductor optical waveguides as a source of

correlated photon pairs, in collaboration with the Laboratory for Physical Sciences of the University of Maryland.

Contact: Dr. Joshua C. Bienfang

[301] 975-2105

joshua.bienfang@nist.gov

'March Madness' Effects

Observed in Ultracold Gases

We have discovered new quantum phases

in ultracold gases that reveal the competition between two major mechanisms of

electrical resistance in solids: crystalline

disorder, and the interactions between

electrons. In "March Madness" terms, basketball fans who arrive early to an empty

stadium can move relatively quickly down

any row unless they encounter a railing,

wall, or other barrier (analogous to crystal

disorder). But once the game begins, a fan's movements are constrained along rows by

other fans already occupying seats (analo- gous to electron blocking). Even though
8 NIST Physics Laboratory

Phillip Anderson and Sir Neville Mott won Nobel Prizes in 1977 for the theory

of these phenomena in metals, it has been

difficult to observe their effects in real T

materials.

Quantum phases of hard-core bosons confined in a one-dimensional quasiperiodic

potential were studied within the theoretical framework of intensity interferometry

(Hanbury Brown-Twiss interferometry).

The quasiperiodic potential induces a cas- cade of Mott-like band-insulator phases, in addition to the more familiar Mott insulator, Bose glass, and superfluid phases. The new phases are incompressible and have

zero superfluid fraction. At critical filling

factors, the appearance of these insulating

phases is heralded by a peak to dip transition in the interferogram, which reflects the fermionic aspect of hard core bosons.

In the localized phase, the interference pattern exhibits a hierarchy of peaks at the

reciprocal lattice vectors of the system. Our

study demonstrates that, in contrast to measurements of the momentum distribution, intensity interferometry provides an

effective method to distinguish Mott and

glassy phases.

Figure B. Representation of the interference

of wave patterns created by atoms that have been released from an optical lattice with disorder. The complex shape of peaks

and valleys is an example of a natural fractal pattern, a pattern that continues to reveal new details no matter how many times it is magnified.

Contact: Dr. Charles W. Clark

(301] 975-3708

charles.clark@nist.gov

fhe third strategic focus is

to develop techniques for

fabricating nanostructures and

measuring their electronic and

magnetic properties.

NANOSCALE

ELECTRONICS AND

MAGNETICS

INTENDED GUTCGME AND

BACKGROUND

The intended outcome of this work is the continuous improvement of methods for

fabricating and characterizing nanometerscale electronic and magnetic structures, as required to meet current and future needs of the semiconductor and data storage

industries.

Our main tools for pursuing this program

are scanning electron microscopy with

polarization analysis (SEMPA) and the scanning tunneling microscope (STM). The

Electron Physics Group in the Division has been a leading innovator in both of these methods, which are outgrowths of work be- gun at NIST in the 1970s. SEMPA enables

us to use conventional scanning electron microscopy (SEM) to image nanometerscale magnetic structure, through spinpolarization analysis of secondary electrons

ejected from the sample. It has several unique capabilities that distinguish it from

other magnetic imaging techniques: it is a highly sensitive, nonperturbative method,

and thus is especially well suited for in situ

studies of surface and nanostructure magnetization; it provides a direct measurement

of the magnetization of a material region,

rather than of a magnetic field; it has the

high spatial resolution (about 10 nm), long

working distance, and large depth-of-field

characteristic of SEM; and it facilitates simultaneous measurements of the magnetization and the topography. SEMPA studies have led to a number of breakthroughs in understanding the basic mechanisms of

magnetism on the micro- and nanoscale,

and have also addressed near-term measure- ment issues faced by the magnetic data

storage industry.

Our STM program is focused on understanding the electronic and magnetic

properties of nanostructures on surfaces. In recent years the STM program has been

particularly concerned with the magnetic

multilayer materials that have been investi- gated by SEMPA. The complementarities

of SEMPA and STM measurements have

elucidated many connections between conditions of layer growth and magnetic device performance.

The main, current direction of the STM

program is the course of research made possible by the recently completed Nanoscale

Physics Laboratory. This laboratory permits

us to measure quantum electronic structures with atomic-scale imaging resolution and

high electron-energy resolution. Samples

grown in situ can be measured in an ultra- high vacuum environment with magnetic

fields of up to 1 0 T at temperatures down to 2.3 K. Additionally, a program in Autono- mous Atom Assembly is underway that allows us to fabricate highly complex and

perfect nanostructures on demand.

The work reported below was performed by

the Electron Physics Group. In 2006, the NIST Director selected the Electron Physics

Group to serve as the nucleus for a new NIST Center for Nanoscale Science and

Technology (CNST), which would have primary responsibility for activities associ- ated with the new nanofabrication facility

in the NIST Advanced Measurement Laboratory complex. In May 2007, CNST was
Electron and Optical Physics Division 9

formally established as a NIST operating

unit, at the same level as the Physics Laboratory and separate from it. We are proud to

see the Electron Physics Group's fine work

recognized at this level. Subsequent reports on their activities will be issued by CNST.

ACCOMPLISHMENTS

Changing the Rings: A Key

Finding for Magnetics Design

We have made the first theoretical determi- nation of the dominant damping mechanism that setdes down excited magnetic

states—"ringing" in physics parlance—in some key metals. These results point to more efficient methods to predict the dynamics of magnetic materials and to improve the design of key materials for magnetic devices.

The ability to control the dynamics of

magnetic materials is critical to high-perfor- mance electronic devices such as magnetic

field sensors and magnetic recording media.

In a computers magnetic storage—like a hard disk—a logical bit is represented by

a group of atoms whose electron "spins"

all are oriented in a particular direction,

creating a minute magnetic field. To

change the bit from, say, a one to a zero,

the drive's write head imposes a field in a

different direction at that point, causing the

electrons to become magnetically excited. Their magnetic poles begin precessing

the same motion seen in a child's spinning

top when it's tilted to one side and begins

rotating around a vertical axis. Damping is what siphons off this energy, allowing the

electron spins to settle into a new orientation. For fast write speeds—magnetization

reversals in a nanosecond or faster—a hard

disk wants strong damping.

On the other hand, damping is associated with noise and loss of signal in the same

drive's read heads—and other magnetic field

sensors—so they need materials with very

weak damping. The design of improved

magnetic devices, particularly at the nanoscale, requires a palette of materials with

tailored damping rates, but unfortunately

the damping mechanism is not well understood. Important damping mechanisms

have not been identified, particularly for the so-called intrinsic damping seen in pure

ferromagnetic materials, and no quantitative

calculations of the damping rate have been

done. So, the search for improved materials must be largely by trial and error.

To address this, we calculated the expected

damping parameters for three commonly

used ferromagnetic elements, iron, cobalt, and nickel, based on proposed models

that link precession damping in a complex

fashion with the creation of electron-hole

pairs in the metal that ultimately dissipate the magnetic excitation energy as vibration energy in the crystal structure. The calculation is extremely complex, both because of the intrinsic difficulty of accounting for

the mutual interactions of large numbers

of electrons in a solid, and because the phenomenon is inherently complex, with at

least two different and competing mechanisms. Damping rises with temperature in

all three metals, for example, but in cobalt and nickel it also rises with decreasing temperature at low temperatures.

Figure 7. Damped precessional motion

of the magnetization represented on

the surface of a sphere. The red curve shows the direction of the magnetization

precessing around its equilibrium direction. On the left, the amplitude of the precession

steadily decreases due to the presence of magnetic damping. Qn the right, a steady

state precession amplitude is reached due

to the presence of an alternating applied

magnetic field balancing the damping.

By comparing the calculated damping effects with experimental measurements, we

were able to identify the dominant mechanisms behind intrinsic damping in the

three metals, which at room temperature

and above is tied to electron energy transitions. The results point to materials design

techniques that could be used to optimize

damping in new magnetic alloys.

Contact: Dr. Mark D. Stiles (301)975-3745

mark.stiles@nist.gov

Speed Bumps Less Important

Than Potholes for Graphene

For electrical charges racing through an

atom-thick sheet of graphene, occasional

hills and valleys are no big deal, but the potholes—single-atom defects in the

crystal—are killers. This conclusion comes

from detailed maps of electron interference patterns in graphene that show how defects

in the two-dimensional carbon crystal

affect charge flow through the material. The results have implications for the design

of graphene-based nanoelectronics.

A single layer of carbon atoms tightly

arranged in a honeycomb pattern, graphene was long thought to be an

interesting theoretical concept that was

impossible in practice—it would be too

unstable, and crumple into some other

configuration. The discovery, in 2004, that graphene actually could exist touched off

a rush of experimentation to explore its

properties.

Graphene has been described as a carbon

nanotube unrolled, and shares some

of the unique properties of nanotubes.

In particular, it's a so-called ballistic conductor, meaning that electrons flow through it at high speed, like photons

through a vacuum, with virtually no

collisions with the atoms in the crystal.
1 0 NIST Physics Laboratory

1

Figure 8. Comparison of an STM topographic image of a section of graphene sheet [top

left] with spectroscopy images of electron interference at three different energies. Strong

interference patterns are generated by atomic scale defects in the graphene crystal (red arrows] but only modest disturbances are caused by larger scale bumps in the sheet [blue arrows.) Analysis of the ripples shows that the electron energy in graphene is inversely

proportional to its wavelength, just like light waves. The area imaged is approximately

40 nm square.

This makes it a potentially outstanding

conductor for wires and other elements

in nanoscale electronics. Defects or

irregularities in the graphene crystal, however, can cause the electrons to bounce

back or scatter, the equivalent of electrical

resistance. So one key issue is just what

sort of defects cause scattering, and by how

much?

To answer this, we grew layers of graphene on wafers of silicon carbide crystals and

mapped the sheets with a custom-built

scanning tunneling microscope (STM)

that can measure both physical surface

features and the interference patterns caused by electrons scattering in the

crystal. (Graphene on silicon carbide is

a leading candidate for graphene-based

nanoelectronics.)

The results are counter-intuitive.

Irregularities in the underlying silicon carbide cause bumps and dips in the graphene sheet that lies over it rather

like a blanket on a lumpy bed, but these

relatively large bumps have only a minor

effect on the electron's passage. In contrast, missing carbon atoms in the crystal lattice cause strong scattering, the interference patterns rippling around them like waves

hitting the piles of a pier. From a detailed

analysis of these interference patterns, the team verified that electrons in the graphene

sheet behave like photons, even at the nanometer scale.

Contact: Dr. Jason N. Grain

(301)975-3744

jason.crain@nist.gov

'Atomic Switch' Experiments

Expand Nanoscale Toolkit

We have used a beam of electrons to move

a single atom in a small molecule back and

forth between two positions on a crystal

surface, a significant step toward learning

how to build an "atomic switch" that turns

electrical signals on and off in nanoscale

devices.

A custom-built, cryogenic scanning tunneling microscope (STM) was used to perform several different types of atomic

scale measurements and manipulations. A

molecular chain of one cobalt atom and

several copper atoms was constructed,

atom by atom, on a surface of copper atoms using the STM to move the atoms. Then the STM was used to shoot electrons

at the molecular chain, and its effect on

the switching motion of the cobalt atom

was measured. Theoretical calculations of

the atoms' electronic structure confirmed

the experimental results.

We used a new technique called "tunneling

noise spectroscopy"—based on our 2004

discovery that an atom emits a characteristic scratching sound when an STM is used

to move the atom—to determine how long

the atom stays in one place. We found that

a single electron boosts the molecule above

a critical energy level, allowing a key bond

to break so the cobalt atom can switch positions. The cobalt atom was less likely to switch as the molecular chain was extended

in length from two to five copper atoms,

demonstrating that the atom switching

dynamics can be tuned through changes in the molecular architecture.

I
Electron and Optical Physics Division 1

1

\ ^[

^

m

a

I •

p.-

0.5 nm

fee Quantum Yield [x 10"

]

Figure 9. [a] An STM moves a single cobalt

atonn (blue sphere] in a small molecule back and forth between two positions on a

crystal surface, [b] Switching is most likely when the STM tip is positioned to the left of the cobalt atom (blue and white speckled

area].

We also found that the position of the STM tip is critical—switching is most

likely when the STM tip is positioned to the left of the cobalt atom. This insight

raises the possibility that molecular orbital

analysis may be used to guide the design

and control of single atom manipulation in nanostructures.

Contact: Dr. Joseph A. Stroscio

(301] 975-3712

joseph.stroscioOnist.gov

Laser Trapping of Erbium May

Lead to Novel Devices

We have used lasers to cool and trap erbium atoms, a "rare earth" heavy

metal with unusual optical, electronic,

and magnetic properties. The element

has such a complex energy structure that

it was previously considered too wild to

trap. This demonstration might lead to the development of novel nanoscale devices for telecommunications, quantum computing,

or fine-tuning the properties of semiconductors.

Laser cooling and trapping involves hitting atoms with laser beams of just the right color and configuration to cause the atoms

to absorb and emit light in a way that leads

to controlled loss of momentum and heat, ultimately producing a stable, nearly motionless state. Until now, the process has been possible only with atoms that switch

easily between two energy levels without any possible stops in between. Erbium has over 1 1 0 energy levels between the two

used in laser cooling, and thus has many

ways to get "lost" in the process. We dis- covered that these lost atoms actually get

recycled, so trapping is possible after all.

Erbium atoms were produced by an oven at 1300 °C. Magnetic fields and six counter-propagating purple laser beams

were then used to cool and trap over a million atoms in a space about 100 pm in diameter. As the atoms spend time in the

trap, they fall into one or more of the 110

energy levels, stop responding to the lasers, and begin to diffuse out of the trap. Recycling occurs, though, because the atoms

are sufficiently magnetic to be held in the

vicinity by the trap's magnetic field. Eventually, many of the lurking atoms fall back

to the lowest energy level that resonates with the laser light and are recaptured in the trap.

Figure 10. A purple laser beam slows erbium atoms [the purple beam traveling

right to left) emerging from an oven at

1 300 °C, in preparation for trapping and

cooling.

The erbium atoms can be trapped at a density that is high enough to be a good starting point for making a BoseEinstein condensate, an unusual, very uniform state of matter used in NIST

research on quantum computing. Cold

trapped erbium also might be useful for producing single photons at wavelengths

used in telecommunications. In addition, trapped erbium atoms might be

used for "doping" semiconductors with

small amounts of impurities to tailor

their properties. Erbium—which, like other rare earth metals, retains its unique

optical characteristics even when mixed

with other materials—is already used in

lasers, amplifiers, and glazes for glasses

and ceramics. Erbium salts, for example,

emit pastel pink light.

Contact: Dr. Jabez J. McClelland

(301)975-3721

jabez.mcclelland@nist.gov
GOAL

To determine atomic properties

and investigate fundamental

quantum interactions

Atomic Physics Division

The strategy of the Atomic Physics Division is to develop and apply atomic physics

research methods, including the interaction between atoms and electromagnetic . fields, to achieve fundamental advances in measurement science—some at the quantum limit— relevant to industry and the technical community, and to produce

and critically compile physical reference data.

Thefirst strategic element

is to advance the physics of

electromagnetic-matter interactions,

to explore new applications for laser

cooled and trapped atoms, to study

exotic states of matter, and to study

and control many-body quantum

systems.

LIGHT-MATTER

INTERACTIONS AND

ATOM OPTICS

INTENDED OUTCOME AND

BACKGROUND

This strategic element focuses on the physics and applications of laser cooling

and electromagnetic trapping of neutral

particles, the manipulation of Bose-Einstein condensates (BECs), and the use of optical

dipole forces as a new tool for analyzing

microscopic objects in biochemistry. It includes both fundamental studies, like the

investigation of superfluidity and applied

studies, such as quantum information

processing and measurement techniques for biomolecular systems. A strong theoretical- experimental collaboration is aimed at inter- preting experimental results and providing

guidance for new experiments.

The development of laser cooling and trap- ping techniques, much of which was done

at NIST, allows exquisite control over the motion of atoms. Such control has been ex- ploited to build more precise atomic clocks and other precision measurement devices at NIST and elsewhere. These techniques also enable the study and manipulation of atoms and molecules under conditions in which

their quantum or wave behavior dominates.

This research has revolutionized the field of

matter-wave optics.

Theoretically and experimentally, our programs aims to understand and exploit: Bose-Einstein condensation of neutral atoms; matter-wave optics; optical and

magnetic control of trapped, ultracold atom

collisions; advanced laser cooling and colli- sion studies for atomic clocks; the quantum

behavior of atoms in optical lattices, includ- ing studies in one-, two-, and three-dimensional systems, and simulation of condensed

matter models with cold atoms; quantum

information processing; quantum computing architectures; and optical characteriza- tion and manipulation of single molecules,

biomolecules, and biomembranes.

The Atomic Physics Division is at the center of the newly established Joint Quantum

Institute between the NIST Physics

Laboratory, the Physics Department of the University of Maryland, and the Laboratory

of Physical Sciences of the National Security

Agency. The Chief of the Atomic Physics Division also coordinates NIST s program

in quantum information science, which

includes activities in the Physics Laboratory,

the Electronic and Electrical Engineering

Laboratory, and the Information

Technology Laboratory.

ACCOMPLISHMENTS

Quantum SWAP Operation with

Neutral Atoms as Qubits

Two outstanding problems in neutral atom quantum computing have been the ability

to address atoms in an optical lattice and
Atomic Physics Division 1

3

the demonstration of controlled two-atom

interactions. We have used a novel, two-period lattice to demonstrate both processes.

In one experiment, published in Physical

Review Letters, we used the state-dependent,

two-period "double well" lattice to selectively address the spins (acting as qubits) in only one of the sublattices, despite the wells being only 400 nm from each other. In another experiment, published in Nature, we

used the double well to isolate and control

pairs of atoms, forcing them to interact in

a state-dependent manner (making use of

quantum exchange symmetry) that gives

rise to the entanglement needed for quan- tum computing. These experiments were

both the first of their kind, and represent

a significant step forward for neutral atom

quantum computing.

Figure 1 . Artist's conception of pairs of opposite-spin atoms (qubits] brouglnt

together in an optical lattice to be entangled

by their atom-atom interactions.

Contact: Dr. James [Trey] Porto (301) 975-3238

trey.porto@nist.gov

Control of Cold Quantum Gases

Many recent atomic physics experiments have used magnetic-field control of scattering resonances to modify the properties

and dynamics of ultracold, atomic quanmm

gases such as Bose-Einstein condensates or mixmres of fermions. These resonances occur when the energy of a bound state of two

atoms is tuned to the same energy as that of

two separated cold atoms. Such resonances can be used to make cold molecules and molecular Bose-Einstein condensates, to strongly

modify the nature of superfluid atom pairing, and to modify the properties of atoms

trapped in optical lattices. Such phenomena

are relevant to fimdamental physics, con- densed matter (solid state) physics, atomic

clocks, and quantum information.

(D Q

Adiabatic - Regime '^''z

Coherent Regime

Rogue

Dissociation Regime

Laser Intensity

Figure 2. The different regimes for coldcollision photoassociation. Here f ^ is the time

scale on which the overall density of the gas

evolves when the light is turned on, is the time scale for coherent oscillations between

atomic and molecular populations, is time

scale over which the transient response

to the turning on of the light is completed,

and f^. is the time scale for spontaneous

emission of light by the excited molecules.

We have quantitatively characterized such

resonances for a number of ultracold gases and developed simple physical models for understanding them. Recent work has

characterized optically induced scattering resonances for laser control of quantum

gases of alkaline earth species such as Sr or Yb, which are of great interest for next- generation atomic clocks. One specific application has been to the temporal dynamics of an atomic Bose-Einstein condensate

when pairs of atoms are converted into molecules by photoassociation. We identify

three main photoassociation regimes that can be understood on the basis of time- dependent two-body theory. In particular,

the so-called rogue dissociation regime,

which has a density-dependent limit on

the photoassociation rate, is identified with

a transient regime of the two-atom dynamics. We have determined how the various regimes could be explored by photoassociating condensates of alkaline-earth atoms.

Contact: Dr. Paul S. Julienne

[301] 975-2596

paul.julienne@nist.gov

Coherent Optical Generation

of Vortices in a Bose-Einstein

Condensate

Vortices (micrometer-size whirlpools)

in a quantum superfluid carry angular

momentum, quantized in units of fl. The

first vortices in Bose-Einstein condensates (BECs) were created at NIST-Boulder, and

they are now routinely made by mechanically stirring the atomic gas.

Figure 3. Absorption image of a Na BEG

vortex state, taken along the axis of the LG

beam, generated by transferring h of optical

orbital angular momentum to each BEG

atom.

We have developed a new, well-controlled, coherent method of vortex creation. Light can carry both "spin" angular momentum, associated with its polarization and

"orbital" angular momentum (OAM)

associated with its stial mode. In particular,

Laguerre-Gauss (LG, donut) modes of laser beams carry OAM per photon quantized in

units of h.
14 NIST Physics Laboratory

In work published in Physical Review Letters we used a two-photon Raman process to induce BEC atoms to coherently absorb the OAM of an LG beam, creating a vortex. We verified the coherence of the process by creating and interfering superpositions

of different vortex states, showing that the

relative phase between the states is deter- mined by the relative phase of the optical

fields. We also created vortices of higher

angular momentum by transferring to each atom the orbital angular momentum of two photons.

Contact: Dr. Kristian Helmerson

[301] 975-4266

kristian.helmerson@nist.gov

A Quantum Phase Transition

with Cold Atoms

The Mott insulator is a remarkable phase

of matter, where the interactions between atoms in an optical lattice lead to a state with an exact number of atoms per lattice

site (e.g., one). This state is central to our quantum information program where the Mott state is the initial state. Any deviation from one atom per site will decrease the

fidelity of subsequent quantum gates.

To extend our understanding of Mottinsulator physics we recently undertook a detailed study of the insulating phase in a 2-D system. (A 1-D optical lattice divides the system into an array of 2-D subsys- tems, and a second 2-D lattice provides a corrugated potential in each subsystem.) This work, published in Physical Review

Letters, focused on the momentum distri- bution of the atoms, finding that in the

insulating phase the distribution agreed

quantitatively with theory. In addition, we

probed the size of the insulating region

by measuring correlations in the noise of

atom cloud images.

Contact: Dr. Ian Spielman

[301] 975-8664

ian.spielman@nist.gov

Relative-lntensity-Squeezed

Light for Measurement and

Quantum Applications

We have discovered a nonlinear optical scheme (nondegenerate four-wave

mixing) that robustly generates strongly

squeezed light in a simple Rb vapor cell. This technique represents an important

advance over the best previous atomic

vapor results (-2.2 dB for vacuum quadrature squeezing) , and presents new opportunities both in purely optical experiments

(e.g., quantum optics, interferometry for precision measurements) and in light-atom

interactions (e.g., quantum atom optics,

and precision spectroscopy).

Figure 5. Squeezing versus transmission and

gain. The solid spheres show the squeezing

measured at 1 MHz, for different cell temperatures, 1 09 ""C [blue], 11 2 °C [red], and

1 1 4 °C [black], as the detuning of the pump

laser is scanned. The projection onto the x-y plane shows contour lines of the theoretical squeezing at 2 dB intervals from +4 to -8

dB, and the projections of the data points.

We create two light beams whose intensity difference is squeezed by -8 dB (noise ~

15 % of the usual shot noise). We have

demonstrated low (detection) frequency

squeezing down to below 5 kHz, a remarkable feat considering that OPO technology

took about 1 5 years to demonstrate this. The light is narrowband and nearly reso- nant with the Rb atomic transition.

(a) Momentum Distributions

(b) Noise Correlations

X Momentum [/cj Shallow Lattice Deep Lattice

Figure 4. Momentum [a] and noise correlations [b] in a 2-D Mott insulating system,

in units of single-photon recoil momentum.
Atomic Physics Division 1

5

This light should be particularly useful in "quantum atom optics" experiments where we will interact nonclassical light with atoms to produce nonclassical matter-wave

beams. We also foresee applications to atomic "quantum memory" applications

for quantum information processing.

Contact: Dr. Paul Lett [301] 975-6559

paul.lett@nist.gov

Figure 6. From left to right, an optical tweezer pulls a nanotube from the left side of a polymersome at -1 0 pm/s. The white scale bar at left indicates 1 0 pm.

Optically Directed Formation of The nanotubes have a water-filled core Robust Polymer Nanotubes approximately 80 nm in diameter and are up to 1 cm long. Optical tweezers maNanotubes, like the carbon tubes used in nipulation creates networks of nanotubes

high-strength materials, are among the and vesicles, systems that hold promise for most promising structures in nanotechnol- nanofluidics and other biotech applicaogy. Naturally occurring phospholipid and tions. The results were published in the

protein nanotubes can transport genetic Proceedings ofthe National Academy of

material between cells, viruses, and bacteria. Sciences. Transport of biological molecules through

nanotubes is a particularly exciting prospect Contact: Dr. Kristian Helmerson

for biotechnology applications. [301 ] 975-4266

kristian.helmerson@nist.gov

We have created robust, biocompatible

nanotubes by directed self-assembly. Start- ing with a polymer vesicle (polymersome)

having a hydrophilic/hydrophobic bilayer

membrane, we use optical tweezers (a focused laser beam that grabs dielectric material) to pull on the membrane. Poly- mer molecules in the distorted membrane

rearrange to form long polymer nanotubes,

which we stabilize by chemical crosslinking.

[he second strategic element

is to advance measurement

science at the atomic and nanometer

scale, focusing on precision optical

metrology, the quantum optics of

nanoscale systems, quantum devices,

nanoscale plasmas, and nanooptical

systems.

NANOSCALE AND

QUANTUM METROLOGY

INTENDED GUTCGME AND

BACKGROUND

This strategic element focuses on developing and exploiting precision metrology at the interface between atomic and nanoscale systems. Systems under study include quantum dots and wires, the quantum

optics of nanosystems, ultracold atomic

quantum gases, metallic nanoparticles,

and those with nanoscale features induced on surfaces by highly charged ions. Such

systems arise in advanced 193 nm and

157 nm lithography, plasma etching of

semiconductor wafers, nanolasers, detectors, biomarkers and sensors, nanomaterials, quantum devices and quantum

information, and atomic clocks.

Our research combines theory and

experiment. Theory is used to extend the fundamental understanding of systems at the atomic/nanoscale interface as necessary

to interpret experiment, to explore new

applications in nanoscale and quantum

technologies, and to motivate new and

enhanced precision metrology. We are developing the theoretical understanding

needed to create nanooptics structures that
16 NIST Physics Laboratory

will be needed in emerging quantum and

nanoscale technologies.

Experiment is used to develop new preci- sion measurement tools for this regime,

to collect precise data essential for the

applications mentioned, and to further the understanding of these systems.

We are now expanding our expertise by

beginning to probe the transport, optical,

and mechanical properties of nanoscale and quantum-coherent systems. We are developing the precision metrology needed

to make accurate optical measurements

of individual quantum nanosystems. We

have made the precise measurements of the

refractive index of high index fluids needed

by the semiconductor industry to develop

immersion lithography for sub- 100 nm

optical lithography.

ACCOMPLISHMENTS

Designing the Nanoworld:

Nanostructures, Nanodevices,

and Nanooptics

Developing and exploiting precision metrology for quantum and nanotechnology

requires nanoscale modeling of ultrasmall

structures, devices, their dynamical operation, and their response to probes.

Atomic-scale simulations of the electronic and optical properties of complex nanosys- tems at the nano/molecular interface are being carried out. These systems include

nanocrystals, self-assembled dots, nanodot

arrays and solids, and bio/nanohybrids.

These simulations provide benchmarks for

precise experimental tests of the atomicscale sensitivity of nanosystems. The work

is providing the foundation needed to build design tools for engineering nanolasers, detectors, biomarkers and sensors, quantum devices, and nanomaterials. For

example, recent work has demonstrated

the critical importance of strain, even in

the smallest nanocrystals, for understanding the optical properties of these systems.

Nanoscale simulations of optical fields near nanosystems are also being carried

out. Results are being used to design

nanoprobes and nanocavities, for use in precision nanooptics metrology. Results are

also being used to design and model the nanooptics highway, that is, a collection of

nanoparticles used to generate, transport, and collect photons on the nanoscale, well below the diffraction limit that governs the

classical transport of photons. Nanooptics

highways will be critical for the quantum

transport of excitations in quantum devices and in the metrology of these devices. Theory is being developed to quantify and

optimize this quantum transport.

Contact: Dr. Garnett W. Bryant

[301] 975-2595

gamett.bryantgin ist.gov

Selectable Resistance Magnetic

Tunnel Junctions by Highly

Charged Ion Modification

Within a broad program to explore

methods to fabricate structures with novel

electronic properties at the nanometer scale, we are using highly charged ions (HCIs) to produce ensembles of nano-features within

magnetic tunnel junctions (MTJs). MTJs

are widely recognized as probable long-term

solutions to the magnetic recording industry's need for ultrasensitive magnetic sensors

for use as new hard drive "read" heads.

Thie leading technical challenge is producing

MTJs whose resistance-area (RA) product

(two dimensional resistivity) falls in a range

that allows for both high signal-to-noise

and large bandwidths. Contemporary ap- proaches have focused on producing MTJ

layer structures with uniform RA products, whereas our approach is to produce a layer

structure that is a superposition of high and

low RA product regions, whose average RA product is determined by the relative density of each region.

Our strategy is to irradiate high quality oxides with very dilute doses of HCIs, thereby

introducing local regions of reduced or ablated oxide at each ion's impact site. The

HCI impact sites result in a very low RA

product compared to the high RA product of the regions that were not struck by

ions. The RA product of the HCI modified

oxide is selected by the dose of HCIs. For

example, 100 HCIs per square micrometer

have been found to reduce the RA product

by a factor of 100.

Contact: Dr. Joshua M. Pomeroy

[301] 975-5508

joshua.ponneroy@nist.gov

Laser Cooling of

Nanomechanical Systems

Using conventional cryogenic techniques,

it is possible to cool nanoscale mechanical

resonators to the point that their mechanical modes are near the quantum ground

state. To actually reach the ground state, and to be able to measure and control the motion, we use a quantum dot embedded

in the mechanical resonator to couple its mechanical energy to optical radiation. The mechanical motion of the resonator modifies the energy spectrum of the quan- tum dot in a manner analogous to that in which the optical spectrum of a trapped

ion is modified by its motion about its equilibrium position. By detuning an

incident laser beam to the red-shifted motional sideband, trapped ions can be

laser cooled to the quantum ground state of the trap. A similar result is predicted for the system comprised of the nanomechanical resonator with an embedded quantum

dot. In both cases, the final temperature is determined by spectroscopic measurement

of the fluorescence.
Atomic Physics Division 1

7

Figure 7.

[a] Monolithic

titanium cylinder

housing sample

and collection

optics;

[b] Sample

package

containing wafer with quantum dots;

[c] Electrodes

fabricated to generate surface

acoustic wave.

We are implementing this cooling process. The first step is to study the optomechanical coupling of a high-frequency acoustic wave to a quantum dot. We have fabri- cated a device, as shown in Fig. 7, which

creates a surface acoustic wave on a sample

containing many quantum dots; one

individual dot will be isolated spectroscopically. We have constructed a microscope to capture the dot fluorescence with an optical fiber. The entire microscope is cooled to below 4 K in high vacuum in a closed-cycle cryostat.

The spectroscopy is demanding; the signal

is weak (a single quantum emitter) and the

resolution required is more than an order of magnitude higher than that provided

by grating spectrometers conventionally

used in quantum dot spectroscopy. We

have built a Fabry-Perot cavity with a resolution of 50 MHz and a throughput of

better than 90 %. The cavity transmission

is collected by a single-photon counting

module. We use the cavity in tandem with

a grating monochromator to unambiguously see the emission of a single quantum

dot.

Contact: Dr. John R. Lawall (301)975-3226

john.lawall@nist.gov

A Few Quantum Dot, UltralowThreshold Laser

Stimulated emission and lasing are by

nature cooperative phenomena and typically involves large number of emitters. A

single-state laser not only represents an interesting limit to the number of contribut- ing states, it also ofi'ers a way to probe the

system's characteristics as it moves from a continuous distribution of states, to a discrete distribution, to finally a single state. There are also technological motivations

to this endeavor, as more efficient lasers requiring smaller numbers of emitters will have an impact in a variety of technologies.

A single-state laser has been recently observed in atomic systems, but requires the preparation of an ensemble of atoms in

the same state. This has not been observed

in solids. We have shown lasing in solids

in which only a few states contribute to

the lasing action. We use semiconductor quantum dots (QDs) placed in a high

quality factor (Q) optical microcavity. The

cavity is a microdisk structure with a diameter of 1.8 \im, and supports whisperinggallery modes in the vicinity of disk perimeter. The Q exceeds 15,000. The microdisk

and simulation of the cavity mode is shown

in Fig. 8.

Figure 8. SEM image of 1 .8 pm diameter

microdisk cavity. Insert: Top-view simulation showing whispering gallery cavity modes.

We observe discrete QD states in the photoluminescence and we control the position of the QD states with respect to the cavity mode by adjusting the sample

temperature. Even when the cavity mode

is positioned where no apparent state is aligned we observe lasing. Our model

indicates this is due to the coupling of tails of the emitter with the very high Q cavity. However, when the cavity mode is aligned

with an emitter state, the lasing threshold drops by a factor of about 3-4. Because

of off-resonance coupling of the cavity

mode and emitter tails, even when a single

discrete QD state is aligned with the cavity

mode and lases we do not have a purely

single state laser. However, this does repre- sent the first time the alignment of such a

single QD state produces such a dramatic

reduction in laser threshold.

Contact: Dr. Glenn Solomon

[301] 975-3225

glenn.solonnon@nist.gov
18 NIST Physics Laboratory

Thethird strategic element

is to produce reference data

on atomic structure, to critically

compile reference data for scientific

and technological applications, and

to develop techniques to apply the

data to further the understanding of

important plasma devices.

CRITICALLY EVALUATED

ATOMIC DATA

INTENDED GUTCGME AND

BACKGROUND

The objective of this strategic element is to

critically compile fundamental constants and spectroscopic data for atoms from the

far infrared to the x-ray spectral regions.

We disseminate reference data on the Physics Laboratory website and produce

high-quality data for urgent scientific or

technological needs. When reliable data do

not exist for high-priority needs, specific measurements or calculations are undertaken to produce them.

The NIST databases for atomic spectra and fundamental constants are recognized

throughout the world. We regularly add new material to our flagship database, the Atomic Spectra Database, which now

contains data for 141,000 spectral lines and 77,000 energy levels. It experiences over 55,000 requests for data each month.

To assist in the diagnostics of a variety of

plasmas, we added two new databases that contain benchmark data on plasma population kinetics, i.e., properties of ionized

gases. These databases provide researchers with the best available data on numerous plasma parameters, such as mean ion charge state for a plasma under specific conditions. An online computational

system for collisional-radiative modeling

of hot plasmas under diverse conditions was also added, developed with Lawrence

Livermore National Laboratory.

ACCOMPLISHMENTS

Precision Wavelengths for New

Telescopes

The Very Large Telescope No. 1 is one

of the largest of a new class of modern

telescopes for ground-based astronomy.

It is located at the European Southern

Observatory in Chile. One of its important missions is to observe spectra of stars and interstellar media at infrared wavelengths, 950 nm to 5500 nm. To do this

it uses a major new infrared spectrometer,

the Cryogenic High-Resolution Echelle Spectrograph (CRIRES).

The wavelength scale of this spectrometer is established by spectral lines from

a thorium/argon hollow cathode lamp,

similar to the platinum/neon lamp used

to calibrate spectrometers on the Hubble

Space Telescope (HST). Unfortunately,

the spectrum of the Th/Ar lamp has not been well studied in the infrared and not enough accurate calibration lines are available.

To remedy this problem, we made preci- sion measurements of Th/Ar lamps with

our 2 m Fourier transform spectrometer.

The wavelengths are accurate to about

0.00004 nm. With these new measurements, CRIRES will be able to achieve its astronomical goals.

In related work for the Hubble Space

Telescope, we made observations of Pt/ Ne lamps similar to those to be used to

calibrate a new spectrograph to be installed on HST in 2008, the Cosmic Origins

Spectrograph (COS). Since the lamps will be used much more intensively on COS

than on earlier space spectrographs, there was concern as to whether they would last

for the whole mission.

We performed accelerated aging tests on

lamps from the same production run as the COS lamps by running them on an interval timer to simulate their use in space. After each three hundred hours of aging, we used our 10m vacuum ultraviolet spectrometer

to quantitatively measure the spectral

output of each lamp. Each lamp was run

until it failed (about 1000 h). Although the aging is continuing for some lamps, results

to date indicate that the lamps will perform

as needed for COS.

Contact: Dr. Gillian Nave

(301] 975-431

1

gillian.nave@nist.gov

Critical Data for Fusion Energy

Science: Ionization Energies for

Tungsten

Construction of the International Ther- monuclear Experimental Reactor (ITER)

will soon start in France. ITER is expected

to generate fusion power for periods up to 1000 s. It will be the most expensive sci- ence project ever undertaken. An important part of ITER is the divertor, a region

of the vessel that exhausts the flow of

energy from charged particles and removes helium and other impurities. Tiles of the

divertor will be made of tungsten, a material with very high melting point.

Although the tungsten tiles are able to withstand the high temperatures in ITER,

atoms of tungsten will be sputtered into the active gases. To understand the complex processes taking place in these gases, it

is important to determine the populations

of the various ions of tungsten in the gas. For this it is necessary to have reliable val-
Atomic Physics Division 1

9

ues for the ionization energies of tungsten

ions. The ionization energy is the amount

of energy required to eject an electron from a given ion so that it is transformed

to the next higher ion.

Previously, only values for the ionization

energies of tungsten from rough theoretical

calculations were available. We developed

a method to determine accurate values for

all tungsten ions—from neutral tungsten

through almost fully stripped tungsten, W^^*. The method is based on scaling

results of theoretical calculations according to experimental data. Uncertainties vary from 1.7 % for to 0.0008 % for W^^*, wfith typical values about 0.1 %. The

residts are published in Atomic Data and

Nuclear Data Tables.

Contact: Dr. Alexander E. Kramida

(3D1] 975-8074

alexander.kramida(Snist.gov

Critical Data for Fusion Energy

Science: Spectra of Highly

Ionized Tungsten

In order to help meet the need for spectral data of wall materials in the divertor region

of ITER, we excited spectra of tungsten ions with our Electron Beam Ion Trap (EBIT).

Spectra in the x-ray region were measured

with a microcalorimeter, a new type of

spectrometer that detects single photons

and measures the rise in temperature to deduce the energy deposited—and hence

the wavelength. At longer wavelengths, a grazing-incidence spectrometer was used.

A number of new spectral lines were identified. The observed spectra were interpreted

by means of coUisional-radiative modeling of the ionized gas in EBIT. Excellent agreement with the observed spectra was

obtained. Fig. 9 shows a spectrum from the microcalorimeter together with a spectrum

predicted by modeling calculations.

1.0

0.8

0.6

0.4

0.2

0.0

1.0

0.8

0.6

0.4

0.2

0.00

Experiment

W*^* [Cu] W'"^*[Ni] W'* [Co]Modeling

4p

3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Wavelength [nm]

Figure 9. Observed spectrum and

theoretical modeling of x-ray spectra of tungsten. The labels Cu, Ni, and Co refer to the isoelectronic sequences of the stages

of ionization of the lines [Cu: W^*: Ni: W^'^*; Co: W^*]. The letters Bf, 5f, etc. refer to upper electronic configurations of W"'^*. The

line at 0.79 nm is blend of two transitions forbidden to electric-dipole radiation: one is an electric-quadrupole transition, the other a magnetic-octopole transition.

According to the calculations, an important

strong line at 0.79 nm is actually a blend of two forbidden-type transitions. We showed

that electron densities in plasma devices like ITER could be determined by measuring

the ratio of the intensities of these two lines. The results are reported in Physical Review A

and the Journal ofPhysics B.

pointing out the merits of these definitions based on prescribed values of the Planck constant, the elementary charge, the Boltzmann constant, and the Avogadro

constant.

The possible new definitions would have

advantages including providing a stable,

precise, and universal measurement system.

With fundamental constant-based definitions of the SI units in place, the values of many of the fundamental physical constants, which are presently determined by

experiment and theory, would have exact

values, and the uncertainties of many other fundamental constants would be signifi- cantly reduced.

The Fundamental Constants Data Center

has worked with relevant organizations

to promote the changes in the SI. This

includes the Consultative Committee for Units (CCU), the Committee on Data for Science and Technology (CODATA), and

the International Union of Pure and Applied Physics (lUPAP).

Contact: Dr. Peter J. Mohr

[301] 975-3217

peter.mohr@nist.gov

Contact: Dr. Yuri Ralchenko

[301] 975-3210

yuri.ralchenko@nist.gov

Redefinition of the International

System of Units (SI)

In an effort to improve the International System of Units (SI) to overcome deficiencies, the Fundamental Constants Data

Center has published a number of articles describing potential new definitions of

the kilogram, ampere, kelvin, and mole.
jap:

Optica Techno ogy

Division

GOAL

To provide the foundation for

optical radiation measurements

for our Nation

The strategy for meeting this goal is to develop and provide national measurement

standards and services to advance optical technologies spanning the microwave

through the infrared, visible, and ultraviolet spectral regions.

Thefirst strategic element is to

develop and provide optical

radiation standards based on the SI

units.

OPTICAL RADIATION

STANDARDS

INTENDED GUTCGME AND

BACKGROUND

The Optical Technology Division provides

the optical radiation measurement science and standards to aid the advancement and

application of optical technology. In particular, the Division advances, maintains,

and disseminates standards for the candela and kelvin base SI units, and associated photometric, colorimetric, pyrometric,

and spectral radiometric quantities. These

standards benefit industries from aerospace

to lighting, by ensuring the accuracy and

consistency of measurements between and

within organizations.

The Division helps maintain the quality

and international comparability of our Nations optical radiation measurements and

standards by participating in international measurement comparisons with other national metrology institutes (NMIs). These

comparisons are organized through the Consultative Committees on Temperature

(CCT) and on Photometry and Radiometry (CCPR) under the auspices of the International Committee of Weights and

Measures (CIPM).

ACCOMPLISHMENTS

New Spectral Irradiance

Standards from the NISI

Synchrotron Ultraviolet

Radiation Facility, SURF III

To reduce uncertainties in the ultraviolet

spectral irradiance scale, to meet the increasingly stringent demands of the climate remote sensing, semiconductor manufacturing, and health and safety communities, the Division in collaboration with

Electron and Optical Physics Division has developed a highly accurate method for

calibrating deuterium lamps. The lamps

are now calibrated in air from 200 nm to 400 nm using synchrotron radiation from

the NIST Synchrotron Ultraviolet Radiation Facility, SURF III.

The absolute spectral irradiances are calculated from the Schwinger equation using

experimental knowledge of the SURF III electron beam current and beam energy and accurate measurements of the area of

the aperture used in the specification of

the irradiance geometry. The storage ring

is operated at low flux levels to minimize

radiation damage to optical components.

The total expanded uncertainty of the

spectral irradiance from 200 nm to 400 nm is l.3%{k = 2).

Figure 1 . The spectral irradiances of NIST

disseminated deuterium lamp standards,

such as the one on the left, are measured at the Synchrotron Ultraviolet Radiation Facility [SURF III], which creates the light seen on

the right.
Optical Technology Division 21

A comparison of the SURF Ill-based

calibrations with past NIST calibrations shows agreement within the combined

uncertainties. The availability of a new

type of deuterium lamp with relighting

reproducibility of better than 0.1 % allows dissemination of a UV spectral irradiance

scale with lower uncertainties, approximately 1.5 %.

Contact: Dr. Ping-Shine Shaw

[301] 975^41

6

ping-shine.shaw@nist.gov

Total Spectral Radiant Flux

Standards Developed

In response to a request from the Council for Optical Radiation Measurements

(CORM), the Division has developed a new calibration service to disseminate

standards for Total Spectral Radiant Flux, an important fundamental attribute of

light sources. A Total Spectral Radiant

Flux standard allows industry to improve

their measurements of the efficacy of

non-incandescent light sources, such

as solid-state light sources now under

development, for which the amount of

output radiation varies significantly with

wavelength.

We have realized the scale of total spectral radiant flux (W/nm) in the 360 nm to 800 nm region by using a specialized reference goniospectroradiometer to map

the lamp output over the full sphere, as shown in Fig. 2.

The use of a spectroradiometer reduces

the typically dominant measurement error associated with the imperfect matching

of the spectral response of a photometer

to the standard visual response of the eye. The use of a goniometer for mapping

the angular output of the sources provides higher measurement accuracy and

increased information about the angular dependence of the lamp output not

available if an integrating sphere is used

instead, as standard within the lighting

industry.

Figure 2. The NIST goniospectroradiometer

measuring the total spectral radiant flux scale of a lamp. The optical fiber input of an

array spectroradiometer is positioned at one end of the rotating arm. To cover the

full range of angles, the lamp is also rotated around its vertical axis.

The NIST Total Spectral Radiant Flux

scale is tied to the NIST spectral irradi- ance scale for the relative spectral distribu- tion and to the NIST total luminous flux unit or lumen for the absolute spectral

photometric output. Two types of lamps

standards have been made available: 75 W

and 60 Wquartz-halogen lamps. Higher

(200 W) and lower (20 W) power lamps

will be offered in the near future. Customer-provided lamps can also be calibrated. This new service provides national

traceability for total luminous flux, as well as for color quantities of light sources measured by integrating-sphere-based

spectroradiometer systems. The uncertainty in total luminous flux is approximately

0.5 % (^ = 2), and the uncertainty in total

spectral radiant flux ranges from 1.5 % at 360 nm to 0.7 % at 550 nm.

Contact: Mr. Yuqin Zong

[301] 975-2332

yuqin.zongOnist.gov

LBIR Facility Improves the

Accuracy of Missile Defense

Sensors

The Division continues to collaborate with

the Missile Defense Agency (MDA) to ensure that infrared sensors used in missile defense, such as for the Exo-atmospheric

Kill Vehicle or EKV, have the accuracy

necessary to discriminate the infrared sig- nature of an incoming missile from space thermal background or from thermally

emitting decoys intentionally released by

or with the missile during its trajectory.

This work utilizes the Division's state-ofthe-art Low Background Infrared (LBIR)

Facility, which offers a low-temperature

thermal background that mimics the 3 K

thermal background of space. The LBIR

facility is used to directly calibrate MDA

and NIST infrared source and detector standards against the LBIR Absolute

Cryogenic Radiometer (ACR). The NIST

source and detector standards are deployed

to MDA for calibrating test facilities.

The primary NIST detector standard deployed to MDA facilities is the BXR.

Recently, the calibration uncertainty of

the BXR was lowered by a factor of two to 3 % (^ = 1). This reduction was achieved

through the use of a specially fabricated and calibrated silver chloride filter to effectively eliminate out-of-band filter infrared radiation leakage affecting the accuracy of

the calibration transfer from the ACR to the BXR.
22 NIST Physics Laboratory

Figure 3. A blackbody standard being

calibrated by the NIST BXR in the Exo- atmospheric Kill Vehicle [EKV] missile sensor cryogenic test chamber.

The reduced uncertainty helped resolve a

5 % discrepancy between NIST measure- ments and MDA test chamber optical models. The discrepancy was shown to be dominated by inaccurate measurement

of the reflectivity of a mirror in the test chamber and incomplete modeling of the

eflfects of diffraction in the optical system.

Improved mirror reflectance measurements and more accurate diffraction modeling

reduced the discrepancy to 2 %, in line with the overall measurement uncertainty. This level of agreement satisfies present

EKV program needs, and will help ensure

reliable warhead discrimination in the presence of sophisticated decoys.

Contact: Dr. Adriaan Carter [301] 975-4765

adriaan.carter@nist.gov

Thesecond strategic element

is to develop novel optical

measurement methods for solving

problems in critical and emerging

technology areas.

OPTICAL MEASUREMENT

METHODS

INTENDED OUTCGME AND

BACKGROUND

The Division strives to improve the accuracy, quality, and utility of optical measure- ments in burgeoning technology areas, such as nanotechnology, biological and

medical physics, climate change, quantum

information, and national and homeland

security.

In the area of nanotechnology, metal and

magnetic nanoparticles, quantum dots, and nanoshells are being developed for use as quantitative probes to interrogate

and manipulate chemical, physical, and

biological phenomena within complex

biological systems. Raman spectroscopy

is being applied to the determination of

the size homogeneity of carbon nanotubes

separated using advanced chromographic

methods. Such well characterized pure

samples have the potential to serve as stan- dards for researchers exploring applications

of carbon nanotubes which have size-specific chemical and physical properties.

The Division has a strong biophysics

program targeting the development of the

critical measurement science infrastruc- ture for systems biology. Spectroscopy,

microscopy, and other optical technologies

are being developed to characterize and

control interactions between biomolecules.

Such technologies include single-molecule

microscopy, fluorescence resonance energy transfer (FRET), optically trapped

hydrosomes containing single biological

molecules, and THz spectroscopy. The

THz spectroscopic measurements provide

benchmark quantitative measurements of

the large-amplitude vibrational modes in biomolecules important for folding and

function. These benchmark measurements

are compared against state-of-the-art molecular models widely used within the chemical, biotechnology, and pharmaceutical industries. Complementing these molecular and cellular-scale technologies,

hyperspectral imaging and optical scat- terometry are being developed for macroscopic imaging of tissue to improve cancer

diagnosis, guide surgical procedures, and

improve surgical outcomes.

Climate-change research places some of

the most stringent demands on optical radiation measurement due to the need to quantify extremely small changes in the average incident solar radiation, reflected

solar radiation, and outgoing infrared radiation over a decadal time scale. In response to these measurement demands,

the Division has developed expertise in space sensor calibration and standards

in support of the satellite programs of

NASA, NOAA, and USGS. The Division

also works with land- and sea-based sensor programs to help ensure measurement ac- curacy and quality.

The Division has a long history of sup- porting our Nation's national defense by

working with the Calibration Coordination Group of the Department of Defense

to ensure that the standards needs of the

military are met in the area of optical radiation measurement. We have devel- oped specialized calibration chambers to mimic the cold thermal background of

space to ensure the comparability and ac- curacy of the sensor measurements of the

Missile Defense Agency and its aerospace
Optical Technology Division 23

contractors. Correlated-photon sources

are being developed to absolutely calibrate photon-cotinting detectors with applications to quantum communication and

quantum crj^ptography. Such technolog}'

may eventually allow all of the Division's fundamental radiation measurements to be

tied to quantum-based standards.

ACCOMPLISHMENTS

A Practical Method for

Spectral and Spatial StrayLight Correction in Optical

Measurement Systems

The Division has developed a simple and

effective method to correct array spectroradiometers for spectral stray-light errors. Such spectroradiometers are increasingly

used in remote sensing, photometry,

colorimetry, and radiometr}' due to their low cost, compact size, and high measure- ment speed. However, their measurement

accuracy is often less than conventional

monochromator-based systems due to the presence of significant spectral stray light. Such stray light increases the detected

light intensity at wavelengths where the

relative output radiation from the viewed

source is low, leading to significant measurement error.

Figure 4. The stray-light distribution function (SDF) of a typical CCD-based

spectro radiometer.

To implement the NIST stray-light correction method, the spectroradiometer first measures several spectrally narrow laser lines

distributed over the wavelength range of the

instriunent. Due to stray-light effects, the spectroradiometer will detect light not only

at the wavelength corresponding to the laser wavelength, but also weakly in channels corresponding to other wavelengths. Typical data are shown in Fig. 4.

From these data we derive a correction matrix, which is used to reduce measurement

error. This method has been shown to reduce the effect of stray light in commercial array spectroradiometers by as much

as two orders of magnitude, leading to a dramatic improvement in measurement

accuracy.

Contact: Mr. Yuqin Zong

[301] 975-2332

yuqin.zong@nist.gov

Follow-on Satellite Instrument

Calibration Conference

NIST, through its U.S. Measurement Sys- tem Initiative, has cosponsored a follow-on conference to the highly successful "Satellite Instrument Calibration for Measuring

Global Climate Change" conference held

at the University of Maryland in November of 2002. The first conference discussed

the requirements for achieving satellite measurements with sufficient accuracy and

long-term precision to monitor climate change. The report has been widely dis- seminated as NISTIR 7047.

The follow-on conference, "Achieving Satellite Instrument Calibration for Climate

Change" or ASIC^ held in May 2006, was

organized by the Space Dynamics Laboratory of the Utah State University with

additional cosponsorship by the National

Oceanic and Atmospheric Administration

(NOAA) and the National Polar-orbiting

Operational Environmental Satellite Sys- tem (NPOESS) office. The primary goal of

the conference was to develop a calibration

science strategy to achieve the measure- ment requirements determined in the first conference. Breakout groups addressed

the following areas: Infrared Sensors;

Ultraviolet, Visible, and Near Infrared Sensors; Microwave Sensors; Active Sensors; Broadband Sensors; Sensor Intercalibration; and a National Roadmap for Satellite Calibration.

The second report has two overarching

recommendations. The first recommendation is that satellite benchmark missions be initiated to measure Earth's radiation budget, including Earths spectral emission,

its reflectance, and total solar irradiance. The second recommendation is for NIST,

NOAA, and NASA to establish a National

Calibration Center to ensure climatequality measurements in operational and

research satellite missions.

Contact; Dr. Raju V. Datia

[301] 975-2131

raju.datla@nist.gov

Quantum Dot Method Rapidly

Identifies Bacteria

A rapid method for detecting and identifying very small numbers of diverse bacteria, from anthrax to E. coli, has been devel- oped in collaboration with scientists from

the National Cancer Institute (NCI). The

work, described in Proceedings ofthe National Academy ofSciences, could lead to the development of handheld devices for the

rapid identification of biological weapons

and antibiotic-resistant or virulent strains of bacteria.

Traditional ways of identifying infectious

bacteria are time consuming and laborious, requiring the isolation and growth

of a bacterial culture over hours to days.

The new method speeds up the process by using fast-replicating viruses (called bac- teriophages or phages) that infect specific
24 NIST Physics Laboratory

bacteria of interest and are genetically

engineered to bind to "quantum dots." Quantum dots are nanoscale semiconductor particles that provide an intense

fluorescent signal and are less prone to deterioration than conventional molecular

tags when illuminated.

The phages were genetically engineered to produce a specific protein on their surface. When these phages infect bacteria and

reproduce, the bacteria burst and release many phage progeny attached to biotin which is present in all living cells. The

biotin-capped phages selectively attract

specially treated quantum dots, which ab- sorb light efficiently over a wide frequency

range and re-emit it in a single color that depends on particle size. The resulting

phage-quantum dot complexes can be

detected and counted using microscopy,

spectroscopy, or flow cytometry, and the

results used to identify the bacteria. <6

Streptavidin • Quantum dot o

Biotinylated phiage ^

Genetically engineered phage Q

Figure 5. Summary of the new method. A

bacterium bursts following infection with a phage. The phages have been genetically

engineered to express biotin on their surface. The biotinylated phages have an affinity for quantum dots labeled with

streptavidin. The quantum dots fluoresce when illuminated as shown by the bright white spot in the square image.

The new method, summarized graphically

in Fig. 5, can detect and identify as few

as ten target bacterial cells per milliliter of sample in less than an hour. It is more

sensitive than conventional optical methods, and it can count how many viruses are infecting a single bacteria cell or how many

quantum dots are attached to a single virus.

The method could be extended to identify

multiple bacterial strains simultaneously by

pairing different phages with quantum dots

that have different emission colors.

A provisional patent application was

filed through NIST, and more recently a nonprovisional patent application was filed through the National Institutes of Health. The NIST contributions to the work

include experimental design and fluores- cence imaging. The non-NIST collaborators are from NCI, NIH, SAIC, and the National Cancer Institute. This research spun off^ multiple new collaborations with

agencies outside NIST, including the Navy

Medical Research Center (a novel, fieldable method to detect biowarfare agents) and the Nanotechnology Characterization Laboratory of the National Cancer Institute (flow

cytometry standards).

Contact: Dr. Jeeseong C. Hwang

(301) 975-4580

jeeseong. hwangOnist.gov

Magnetic IManoparticles

Assembled into Long Chains

Division scientists have controllably assembled and disassembled chains of magnetic

nanoparticles suspended in a solution. The chains were composed of millions of 12 nm diameter cobalt nanoparticles.

Such particles and their chain structures may have applications in medical imaging, hyperthermia treatment for cancer, and information storage, provided that techniques are available to manipulate and

control their physical and chemical properties and to assemble them into structures. The NIST work is the first to demonstrate

the formation and control of centimeter- long chains of magnetic nanoparticles of a consistent size and quality in a solution.

The nanoparticles were induced to form

linear chains by subjecting them to a weak

magnetic field—about the same strength

as a refrigerator magnet. The particles line up because the nanoparticles act like tiny bar magnets, all facing the same direction

as the applied field. Once this alignment

occurs, the attraction between particles

is so strong that reversing the direction of the applied magnetic field causes the whole chain to rotate 180 degrees. When

the magnetic field is turned off^, the chains

fold into three-dimensional coils. When

the solution is lightly shaken, the chains

fall apart into small rings. The chains were

characterized by optical and transmission

electron microscopy (TEM). ATEM image is shown in Fig. 6.

Figure 6. Tunneling electron microscope

(TEM) image of 12 nm diameter surfactant- coated cobalt nanoparticles ordered by

magnet dipole-dipole couplings.

Magnetic particles have already been

used in medical imaging and information storage, and nano-sized particles may

offer unique or improved properties. For

example, magnetic nanoparticle dyes may

improve contrast between healthy and

diseased tissue in magnetic resonance imaging (MRI), a possibility under study by

a different NIST research group. Research

is ongoing to improve the biocompatibility

of these magnetic nanoparticles.

Contact: Dr. Angela R. Might Walker

(301] 975-2155

angela.hightwalker@nist.gov
Optical Technology Division 25

A Highly Efficient Two-Photon

Source

Division scientists have developed an approach to efficiently create pairs of

photons over a wide range of energy, while minimizing the production of extraneous photons. The approach promises to benefit

applications in physics and technology such as quantum information and

telecommunications.

Paired photons can be generated from a monochromatic light source—albeit very

inefficiendy—in standard optical media

such as glass optical fibers. Most photons

normally travel through glass independently,

without interacting. Occasionally, two of

the input photons will interact, producing

an output photon pair with one higher in energy than the original photons and the other lower in energy by the same amount.

Because the vast majority of photons go

through the fiber unchanged, the relative

intensity of these pairs is low. Since the fiber generates the pairs randomly with a range of possible energies, selecting those photons

with some specific energy fiarther reduces

the number of usefial photon pairs. Typically, the photon pairs in the system must

be detected against the photon noise in the system due primarily to Raman scattering. In Raman scattering individual photons

interact nonlinearly with the phonon modes

of the glass to change their energies. Such

scattering produces undesirable photons

with properties that mimic one of the photons of a photon pair.

To increase the efficiency of photon

pair production while minimizing noise from the extraneous Raman photons,

the NIST two-photon source relies on

a microstructured optical fiber. The

fiber has a slender glass core at the center of an array of hollow channels,

giving a cross-section that resembles a honeycomb. The geometrical structure

of the fiber affects the optical modes of

the fiber, leading to an increase in the

intensity of light in the thin central core with a concomitant enhancement of the photon pair production.

This greater pair-production efficiency reduces the length of optical fiber required, from hundreds of meters to a couple of meters. Moreover, optimization of the size of the channels in the microstructured fiber allows reduction of

the amount of Raman scattering relative to the desired two-photon light production. The result is a source that produces

significantly more pairs of photons over

a wide frequency range, with greatly

reduced contamination by spurious Ra- man photons. A picture of the source is shown in Fig. 7.

T

c1

••Vi.

Figure 7. A microstructured optical fiber

in NIST's new correlated-photon source

delivers high numbers of photon pairs over a broad spectral bandwidth with low

noise in a compact device for quantum

communication applications.

Photon pairs from the new source are being applied to studies of quantum

entanglement and quantum cryptography. These studies take advantage of

the quantum properties of these photon

pairs by which measurements on one of a

pair of photons specifies the measurement

result on the other member of the pair.

Contact: Dr. Alan L. Migdall

[301] 975-2331

alan.migdallOnistgov

fhe third strategic element is to

disseminate optical radiation

measurements and standards to

industry, government, and academia.

OPTICAL MEASUREMENT

SERVICES

INTENDED OUTCOME AND

BACKGROUND

The Division builds and maintains worldclass optical radiation measurement facilities to meet the continued and emerging

needs for standards and specialized measurements by government and industry.

These facilities are available to government

and industry customers through formal

calibration services, special tests, and

standard reference materials available from

NIST Technology Services or through collaborative research efforts.

The Division maintains facilities for measuring optical properties such as

reflectance, retroreflectance, transmittance,

color, and gloss; for photometric measure- ments such as luminous intensity and color temperature; and for radiometric measure- ments such as spectral radiance, spectral

irradiance, spectral power, detector responsivity, and radiance temperature. The

Division has highly specialized facilities for performing low-background radiometric measurements, for characterizing remote

sensing instruments, for measuring the

area of precision radiometric apertures, and

for determining the absolute optical power,

radiance, and irradiance spectral responsivities of instruments. New measurement

facilities have been developed for measuring the emittance and retroreflectance of

materials and for providing standards for

ultraviolet spectral irradiance.
26 NIST Physics Laboratory

ACCOMPLISHMENTS

Hyperspectral Image Projector

for the Calibration of Earth

Remote-Sensing Instruments

Present approaches for cahbrating multispectral and hyperspectral imagers and

sounders, such as those used in climate- change research and weather forecasting, use spatially uniform and temporally

constant optical radiation sources, such as lamp-illuminated integrating spheres, to

fill the foil aperture of the light-collecting

telescope in front of the sensor. Consequently, many systems are not tested prior to deployment with optical signals

that mimic the spectrally, spatially, and

temporally varying signals expected during

operation. Tlie lack of such testing is of

particular concern for satellite imagers due

to their high cost, difficult operating envi- ronment, and inability to be retrieved.

A Hyperspectral Image Projector (HIP)

is being developed to enable the realistic

test, evaluation, and calibration of ground

and space-based optical radiation sensors. The HIP is based on digital micromirror devices (DMDs) commonly found in commercial high definition televisions and

projectors. DMDs consist of 768 x 1024

individually addressable, 1 5 fim square

mirrors.

One DMD is illuminated by a prism or a

grating, which disperses broadband light into a spectrum focused onto the DMD.

The DMD allows 1024 narrow spectral

bands to be modulated in intensity, thus

creating a user-specified spectral distribu- tion of light. A programmable source with

such a high spectral fidelity is essential for

realistically reproducing the spectral content of solar radiation reflected oflF of the

Earth's surface or of the thermal emission

of a chemical-agent cloud. DMDs used for video displays have color-filter wheels to generate visual images. However, the HIP

generates a spectral match, not just a color match.

A second DMD, optically in series with

the first, projects any combination of these

arbitrarily programmable spectra into the

pixels of a (768 x 1024) element spatial

image, thereby producing temporally

integrated images having spectrally mixed

pixels. Calibration of the resulting image

using an absolute spectroradiometer provides the absolute values of the radiance as a function of wavelength, spatial coordinate, and time. This calibrated scene, chosen, for instance, to mimic the view of the ocean by a satellite in a geostationary orbit,

is then directed into the sensor under test.

Contact: Dr, Joseph P. Rice

[301] 975-2133

joseph.nce@nist.gQV

Tool Tackles Translucence and

Other Color Challenges

Special eff^ect paints and coatings, such as some automobile paints, look different depending on illumination or viewing

angles, or both, subtleties that cannot be

accounted for by traditional color measure- ment instruments. To address this defi- ciency in measurement capabilities, NIST

has developed a goniospectrometer that automatically measures the color of light

reflected from a surface as a function of

illumination and viewing angles.

The new goniospectrometer provides more

complete data on the reflection of light

from a color surface, and will be used for calibrating similar instruments and for research on exotic-appearing materials and coatings. A database of measurements

of different materials that could be used

for modeling surfaces that have complex

visual effects will be developed using this new capability. The work is part of a NIST

effort to develop accurate measurement

methods for reproduction and quality control of appearance attributes, includ- ing color matching, by determining the optimal subset of illumination and viewing

geometries needed to accurately characterize the perceived color.

The goniospectrometer, housed in a clean room, illuminates a sample with a range of wavelengths of visible light, every 5 nm

from 360 nm to 780 nm, i.e. from the near ultraviolet/deep blue to red/infrared. The sample and detector are rotated around three axes, allowing illumination and viewing in any direction within

a hemisphere around the sample. The

intensity of the reflected beam is measured

at several hundred locations on a sample

surface, as shown in Figure 8.

L

Figure 8. The NIST goniospectrometer measures the intensity of light reflected from the surface of a sample at 332 points.

A plot of these measurements results in a

different shape depending on whether the

illumination comes from above [top] or at a 60-degree angle [bottom].
Optical Technology Division 27

Based on these measurements, computer

software assigns a numerical value to the

color of the reflected light at each illumi- nation-viewing geometry.

Contact: Dr. Maria E. Nadal

[301] 975^632

maria.nadal@nist.gov

Perceived and Measured Colors

of Retroreflective Materials

used in Traffic Signs

In collaboration with the Federal Highway Administration (FHWA), Division

scientists performed a pilot study to compare measured colors with perceived

colors for roadway signs. The study was initiated in response to anecdotal

observations that instrument-measured

daytime chromaticities of retroreflective materials do not correspond well with

perceived chromaticities.

[c] Robert Rathe

Figure 9. Cameron Miller mounts a STOP sign on the goniometer at the NIST

Center for High-Accuracy Retroreflection Measurements [CHARM].

In the pilot study, instrument measured

appearances were directly compared with

visually perceived appearances. A hue

scaling method was used to measure the

colors perceived by the human subjects

for six different types of retroreflective materials, as well as for a diffuse reference material. The test samples had

chromaticities within the range allowed

by U.S. Federal regulations for yellow

and white traffic signs.

The results of this pilot study were pre- sented at the Quadrennial Session of the International Illumination Commission

(CIE) held in China in July 2007. Overall, instrument measured chromaticities of retroreflective materials corresponded

well with observer reported chromaticities. Both the instrument measurements and a majority of observer data showed

a marked decrease in chromatic satura- tion (colorfulness) for yellow and orange

retroreflective samples, compared to the yellow and orange diffuse refer- ence material. To confirm and expand

these findings, a larger study involving more colors is under development at the FHWA laboratories.

Contact: Dr. Wendy L. Davis

(301) 975-6963

wendy.davis@nist.gov

Implementation of "Once is Enough" at NIST

To help improve the quality and control

the costs of its measurement services, the Division has implemented a "Once is Enough" measurement strategy to elimi- nate unnecessary repeat measurements in

calibrations. Spectral Irradiance Lamps

and Spectral Transmittance Filters are two

of the Division's measurement services in which "Once is Enough" is being applied.

To help Measurement Service customers understand this transition and to aid

calibration laboratories in implementing

a similar approach in their own facilities,

the Division has documented the "Once is Enough" process for the Spectral Irradiance Lamp example in an article in the Journal

ofResearch ofthe National Institute ofStandards and Technology. The implementation

strategy has five critical components: auto- mation, uncertainty budget, measurement

process controls, quality system, and peer

review, described in detail in the article. Careful attention to each of these components provides the calibration scientist with the necessary control over the entire process to confidently eliminate repeat measurements.

The implementation of "Once is Enough"

by calibration laboratories will help lower

costs through reduction in instrument

wear, artifact deterioration, and facility and

staff time associated with each calibration.

Contact: Dr. Howard W. Yoon

[3Q1] 975-2482

howard.yoon@nist.gov
GOAL

To provide the foundation of

ionizing radiation measurements

for our Nation.

Ionizing Radiation

Division

The strategy for meeting this goal is to develop, maintain, and disseminate the national standards for ionizing radiation and radioactivity to meet national needs

for health care, the environment, U.S. industry, and homeland security.

Thefirst strategic element is to

develop dosimetric standards

for X rays, gamma rays, and electrons

based on the SI unit, the gray, for

homeland security, medical, radiation

processing, and radiation protection

applications.

RADIATION DOSIMETRY

STANDARDS

INTENDED OUTCGME AND

BACKGROUND

The Radiation Interactions and Dosimetry Group advances the measurement of

quantities important in the radiological

sciences through programs in the dosimetry of X rays, gamma rays, electrons, and

other charged particles. Its mission is to develop, maintain, and disseminate the national measurement standards for these

radiations, and to engage in research on

radiation interactions and effects to meet

requirements for new standards and to address the needs of industry, medicine, and

government.

We maintain the national standards for the gray (Gy), the Systeme International (SI) unit for radiation dosimetry, and develop,

maintain, and disseminate high-quality data on fundamental radiation interactions. These data are used extensively in radiation transport calculations and simulations, with algorithms and codes often developed by our staff, to solve a wide

range of problems in radiation science and

applications.

Standards are disseminated both directly

to the customer and through networks

of secondary calibration laboratories. We

work closely with such networks to maintain measurement-quality assurance and

traceability, by means of calibrations and

proficiency testing services.

Our staff continues to make important

contributions to the work of national and

international standards and scientific organizations, and we are central to measurement-quality assurance of dosimetry in the many application areas of ionizing radiation. For example, the radiation doses in cancer treatment, radiosurgery, diagnostic

radiology, and public or worker exposures

in the U.S. are traceable to our standards and programs. Our focus on homeland

security continues, while significant progress was made in our more traditional radiation-dosimetry programs.

ACCOMPLISHMENTS

Accelerator Facilities

The Division's accelerator facilities continue to support research efforts in

industrial and medical dosimetry, homeland security, and radiation-hardness and materials-effects studies. Substantial progress has been made in the development of the High-Energy Computed

Tomography (HECT) facility. A number

of hardware and software improvements

were made as a result of collaboration with

engineers from Savannah River National

Laboratory, including the installation of an

object manipulation system consisting of a rotating turntable and a two-dimensional

linear stage. A number of test objects are being assembled, which should allow us

to evaluate the performance of the HECT

imaging hardware and gain expertise in the

use of tomographic reconstruction tools.

ml
Ionizing Radiation Division 29

Figure 1 . Angular "slice" of HECT test object obtained using 1 9 MV x rays from the MIRF

accelerator. A drill bit is clearly observed on

the left side of the image; aluminum support

hardware and mounting holes are apparent

in the center portion of the image.

Quality-assurance resting continues on the Clinac 2100C medical accelerator, typical

of those used in cancer therapy. Using

a recently acquired radiation scanner, depth-dose measurements in water were conducted in order to validate machine

performance. Software controls have been

implemented to allow the beam to be

cycled on and off for a fixed period of time

and a preset number of cycles. This tech- nique will allow frequency-domain analysis

of the response of a second-generation

Domen-type water calorimeter, which will become the primary standard for high- energy absorbed dose-to-water. Plans are

to make use of the Clinac in a high-energy

calibration laboratory based on this primary dosimetry standard.

Contact: Dr. Fred B. Bateman

(301) 975-5580

frecl.batennan@nist.gov

X-Ray Calibration Range

Measurements

The calibration and irradiation of instru- ments that measure x rays are performed

in the NIST x-ray calibration facilities in terms of the physical quantity air kerma.

Calibrations are performed by comparing the instrument to a NIST primary

standard, which includes four free air chambers.

Figure 2. 320 kV replacement x-ray tube.

Air-kerma-measurement comparisons with

the BIPM and other primary standards

laboratories are conducted for quality as- surance. One important comparison began

in 2006. The comparison involved a series of measurements at PTB in Germany and

at NIST using the air-kerma standards and

two NIST reference-class transfer ionization chamber standards. Tungsten and molybdenum reference beam qualities in the range from 10 kV to 50 kV (low energy) were used. This comparison with PTB

will be the third comparison for mammography energies, but the first for NIST

using the recently developed BIPM/CCRI

reference beam qualities. Prior to the next

direct BIPM comparison, the results of

the CCRI beam comparison will verify the new correction factors as applied to the NIST standard for these beam qualities.

In addition to participating in measurement

comparisons, the NIST x-ray facilities are used to conduct proficiency tests for various customers. These include secondary calibration facilities, chamber manufacturers, the nuclear industry, the Department of Energy,

the Department of Defense, private calibration facilities, medical facilities, and the Food and Drug Administration. Calibrations are provided in terms of gray/coulomb

for various reference-quality ionization chambers to achieve traceability to NIST.

Updates made to our website (http://physics.nist.gov/Divisions/Div846/Gp2/gp2.

html) explain the proficiency test policy.

Figure 3. NIST 300 kV calibration range, showing the Wyckoff-Attix free-air chamber

(white assembly], the national standard for medium-energy x-ray beam air kerma.

A new free-air ionization chamber has been designed to realize air kerma for x-ray beams of 50 kV to 300 kV, replacing the Wyckoff-Attix chamber used at NIST as a primary x-ray standard (medium energy) for more than fifty years. The dimensions and

the parallel-plate design of the new chamber

are identical to the Wyckoff-Attix chamber,

but the materials are different. The chamber

incorporates a unique guard bar and insulator design, and precision slides facilitate alignment and the direct measurement

of the air-attenuation correction. Once

the new standard is constructed, it will be

fully evaluated in a parallel measurement

arrangement until the correction factors are

established and tested.

Contact: Ms. Michelle C. G'Brien

[301] 975-2014

michelle.obrienOnist.gov
30 NIST Physics Laboratory

X-Ray Security-Screening

Standards for Homeland

Security

With support from the Department of

Homeland Securit)' (DHS), we have

been developing technical-performance

standards for four classes of x-ray security

screening systems: checkpoint cabinet,

computed tomography, cargo and vehicle,

and human subject. Four ANSI working

groups have been organized to develop national standards for technical performance,

focusing particularly on image quality.

Steel Penetration & Contrast Sensitivity

50 % 75 % ANSI N42.46 Resolution

Figure 4. Objects being considered to test penetration, contrast sensitivity, and

resolution for standards being developed for

x-ray and gamma-ray noninvasive inspection

systems for cargo containers and vehicles.

Each standard will include both test methods and x-ray phantoms appropriate for the application. Examples of artifacts that

are being designed and tested are shown in

Fig. 4. In the upper portion, to test penetration and contrast sensitivity of high- energy inspection systems used to inspect

cargo, the orientation of an arrow must be

determined through increasing thicknesses of steel. The lower portion of the figure

is a test piece proposed to test the spatial resolution of CT imaging systems.

In related work, we have established a testbed for assessing the image quality

of portable x-ray and imaging systems used by bomb squads for explosives and

ordinance detection and disarmament. The

results of testing will be used to establish minimum image-quality standards and

to update a National Institute of Justice standard covering these systems.

Contact: Dr. Lawrence T. Hudson

[301] 975-2537

lawrence.hudson@nist.gov

Testing a Method for

Establishing e-Traceabi!ity to

NIST High-Dose Measurement

Standards

To meet rapid turn-around time needs,

yet maintain high accuracy and minimal

uncertainties, an Internet-based dosimetry

calibration system is being developed for re- motely certifying the calibration of industrial

radiation sources. Using alanine dosimeters and a Bruker e-scan electron paramagnetic

resonance (EPR) spectrometer, subscribers' dosimetry systems will be calibrated to the NIST reference dosimetry system. A

computational method for determining the measurement conversion factor (MCF) relat- ing the NIST reference system to the remote

customer system has been established. The

uncertainty in applying the MCF to the dosimeter response has been evaluated and used

to establish an overall uncertainty budget.

The Internet-based system promises to

deliver immediate certification results to customers, on-demand at lower cost. A

working alpha version was assembled on lab computers and a server within the Division.

Recently, several system design changes were

required to adapt to changes in security

requirements, changes that actually led to a simpler and more user-friendly system. The

next stage will be to transfer the software to Bruker to begin beta testing the system.

Figure 5. Alanine dosimeters used in radiation processing allow for accurate

transfer dosimetry.

A testbed consisting of two separate e-scan spectrometers at NIST is being used to test the MCF calculation method. Calibrated

alanine dosimeters are assembled into a "customer" e-scan dosimeter insert set, as would be used for an actual calibration event, and the results are used to test the MCF computation. Testing the electronic

certification process is conducted by measuring a series of unknown/test dosimeters,

applying the MCF, and calculating dose from the NIST standard reference curve. These tests will be performed for all of

the commercially available inserts and

will serve as guidelines for the operational

aspects of this future service.

Contact: Dr. Marc F. Desrosiers

(301)975-5639

marc.desrosiersdinist.gov
Ionizing Radiation Division 31

Thesecond strategic element is

to develop and provide neutron

standards and measurements needed

for w^orker protection, nuclear power,

homeland security, and fundamental

appUcations.

NEUTRON STANDARDS

AND MEASUREMENTS

INTENDED GUTCGME AND

BACKGROUND

The Neutron Interactions and Dosimetry Group maintains and supports the

nation's premier fundamental neutron

physics user facihties, including a weak

interactions neutron physics station, the Neutron Interferometry and Optics

Facility (NIOF), the Ultra Cold Neutron

Facility (UCNF), an Advanced Monochromatic Neutron Test Facility, and the

nation's only high-resolution Neutron Imaging Facility (NIF) for fuel-cell research. We maintain and disseminate measure- ment standards for neutron dosimeters, neutron survey instruments, and neutron

sources, and improve neutron cross- section standards through both evaluation and experimental work.

The Group is at the forefront of basic research with neutrons. Experiments

involve precision measurements of symmetries and parameters of the "weak"

nuclear interaction, including measuring

the neutron lifetime using both thermal

and ultracold techniques, setting a limit on an important time-reversal-violating

asymmetry coefficient, and characterizing the radiative decay mode of the neutron. These data address fundamental issues

that are important in the understanding

of theories of evolution of the cosmos.

It is an internationally renowned pro- gram that maintains an extensive level of cooperation with premier national and international academic and research

institutions.

The neutron interferometry program

provides the world's most accurate measurements of neutron coherent scattering

lengths, which are important to materials science research and modeling of the nuclear potentials. We recently carried out new interferometry experiments to determine the charge distribution of the neutron and for reciprocal space imaging. We are developing and promoting

the applications of efficient neutron spin

filters based on laser-polarized ^He, and

are pursuing applications for these filters

at NIST as well as at neutron research

centers throughout the U.S.

To support neutron standards for national security needs, we are developing

key technical infrastructure. Advanced

liquid scintillation neutron spectrometry

techniques will lead to characterization of neutron fields and detection of concealed neutron sources with low false-positive

rates. We are planning to organize and

lead a Consultative Committee for Ionizing Radiation (CCRI) comparison of

thermal neutron fluence rate measurements, characterizing four different beam

qualities at the NCNR, and to carry out comparisons of NIST standard neutron

sources. The Group is leading an effort that will result in a new international evaluation of neutron cross-section standards.

ACCOMPLISHMENTS

Active Interrogation Standards

Active interrogation involves directing nuclear radiation into a closed container and measuring secondary radiations to gain information about the contents of

the container. Typically, but not always, neutrons are used as the impinging radiation. Active interrogation has the potential

for detecting smaller quantities of special nuclear materials than is possible by using

passive detectors. It also holds the promise

of detecting nonnuclear materials, hazard- ous chemicals, and explosives.

NIST organized a drafting committee and

held four meetings to prepare a new ANSI

Standard, N42.41, Minimum Performance

Criteria for Active Interrogation Systems

used for Homeland Security, which is being published by the IEEE. A cargo- container testbed with three massive cargo

regions, as needed for testing under ANSI

N42.41, has been set up for use at NIST.

It is capable of mobility to other locations.

Contact; Dr. David M. Gilliam (301) 975-6207

david.gilliamOnist.gov

First Observation of the

Radiative Decay Mode of the

Neutron

Beta decay of the neutron into a proton,

electron, and electron antineutrino is occasionally accompanied by the emission of a photon. An experiment to study

the radiative beta-decay of the neutron was completed at the NG-6 fundamental physics end station. The experiment

employed the magnet previously used for the NIST proton trap neutron lifetime apparatus, with the addition of a detector

for photons with energies above 1 5 keV. A

photon detector that operates efficiently in
32 NIST Physics Laboratory

the high magnetic field, low temperature

environment of the magnet was developed.

This apparatus allowed half of the available

electrons and all of the available protons

from neutron beta-decay to be detected,

which provided a high-rate, backgroundrejecting trigger for the observation of

radiative decay photons. In this first-gen- eration experiment, the photon detector consisted of a single 12 mm by 12 mm by

200 mm scintillating crystal coupled to an

avalanche photodiode.

We observed electron-proton-photon

coincidences that were unambiguously

due to the radiative decay of the neutron. We reported the first observation of the

radiative decay mode, and a manuscript

detailing the measurement was published

in the journal Nature.

Contact: Dr. Jeffrey S. Nico

[301] 975-4663

jeffrey.nicoOnist.gov

Seeing Inside an Operating PEM

Fuel Cell

We are applying neutron-imaging methods

for industrial research on water transport

in fuel cells and on hydrogen distribution

in hydrogen storage devices. This facility has provided critical services to major

automotive and fuel cell companies during

the last few years. This is a high demand

and high profile, nationally recognized program.

Recent advances in neutron imaging detector technology, based on microchannel

plates (MCPs) have resulted in an order-of- magnitude improvement in the achievable neutron image spatial resolution. This enhanced resolution of 25 pm allows the

fuel cell researcher to directly measure the through-plane water distribution in the gas diffusion layer (GDL) and distinguish the water in the anode from that in the cathode in the membrane electrode assembly

(MEA). This was not possible with scintil- lator-based neutron detection. Measuring

the through-plane water distribution gives

insight into the water transport mechanisms in the GDL and MEA. Ongoing

developments of neutron MCP detectors should reach an ultimate resolution of

about 10 pm, which will enable the study

of commercially viable membranes that are from 25 pm to 50 pm thick.

Membrane

Anode Electrode Cathode

Channel Assembly Channel

-1.0 -0.5 0.0 0.5 1.0 1.5 Distance from MEA center [mm]

O -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 Distance from MEA center [mm]

Figure 6. An image of water content in a representative section of an operating PEM

fuel cell, in the "through-plane" dimension. Corresponding water content is shown in the graph.

The initial effort at visualizing the in situ through-plane water distribution of a proton exchange membrane (PEM) fuel

cell was recently published, using an MCP

detector at the thermal neutron imaging

facility at the NIST Center for Neutron

Research, as shown in Fig. 6. The visualization of the through-plane water distribution with a spatial resolution of 30 pm

with neutron imaging was demonstrated.

The analysis suffered from the inability

to resolve the membrane swelling. Future work will focus on mitigating this problem. For instance, thinner membranes

will have a smaller total volume change,

reducing the problem. Additionally, rather than being directly coupled to the detector, the cell will be mounted from the bottom,

providing a reference surface for determining the location of cell components.

Future work with the enhanced resolution

will focus on measuring the GDL porous media properties and their interplay with

the dynamic fuel cell operation. Also, us- ing thick membranes, we will measure the proton conductivity as a function of membrane hydration in an operating fuel cell.

Contact: Dr. Daniel S. Hussey

[301] 975-6465

daniel.husseyOnist.gov

Measurements of the Neutron

Vertical Coherence

We have measured the vertical coher- ence function of a single crystal neutron

interferometer for different vertical beam

distributions. We carried out the measure- ments by introducing a vertical path separation via a pair of prisms placed in the two beam paths of a single crystal neutron

interferometer and measured the loss in

fringe visibility (contrast) as this separation

is increased. This loss of contrast is directly

related to the vertical coherence of the neutron beam. We showed that the measured

coherence length is consistent with the experimental distribution of the incoming

neutron beam momentums in the vertical

direction. We also demonstrated that the

loss in contrast with beam displacement

in one leg of the interferometer could be

recovered by introducing a corresponding displacement in the second leg of the

interferometer.
Ionizing Radiation Division 33

Compensating Phase Wedges Shifter

Displacing Wedges Single Crystal Silicon

Figure 7. Schematic diagram of the coherence length experiment. The neutron

is coherently split and recombined after

traveling two paths.

Results from this experiment raise intriguing possibilities for the development of

Fourier Spectroscopy to enable very precise

direct measurement of vertical momentum distribution of beams reflected from

surfaces and hence allow characterization of various surface properties (as done in normal reflectivity measurements) of a sample. Having a single crystal neutron in- terferometer with a long coherence length

also provides studies coherence scattering over scales that are not easily accessible by

other approaches.

Contact: Dr. Muhammad Arif [301] 975-6303

muhammad.arif@nist.gov

Thethird strategic element is to

develop and provide standards

for radioactivity based on the SI unit,

the becquerel, for homeland security,

environmental, medical, and radiation

protection applications.

RADIOACTIVITY

STANDARDS

INTENDED OUTCOME AND

BACKGROUND

The Radioactivity Group develops and

improves the metrological techniques used

for the standardization of radionuclides. Our mission is to develop, maintain, and

disseminate radioactivity standards, de- velop and apply radioactivity measurement

techniques, and engage in research to meet

the requirements for new standards. We

carry out a wide range of programs in lowlevel standards for environmental measure- ments and monitoring, nuclear medicine,

and radiological instrumentation used for

security.

We continue to lead the national effort,

in collaboration with the Department of

Homeland Security (DHS), to develop

standards and protocols for radiation instrumentation for early and emergency

responders. We are spearheading the development of ANSI standards and

testing protocols for spectroscopic portal

monitors, neutron detectors, x-ray and

high energy gamma-ray interrogation

methods, x-ray imaging, data formats for instrumentation data output, and training standards for responders. The Group has been heavily involved in the testing and

data analysis of advanced spectroscopic

portal monitors (with DHS/DNDO)

at the Nevada Test Site, and is involved with the testing of large-area Nal crystals

to be used in these spectroscopic portal

monitors.

The Group continues to lead an

internationally recognized program for standards in nuclear medicine, providing

the national standards for radionuclides used in 13 million diagnostic procedures

and 200,000 therapeutic nuclear medicine

procedures annually in the U.S. Work

is currently being carried out on the

standardization of two alpha-emitting

radionuclides, -"At and ^^^Ra, that are being investigated for use in targeted

radiotherapy against two difi^erent forms

of cancer. A new initiative, aimed at establishing standards and measurement

support to improve accuracy and

consistency in quantitative Positron Emission Tomography/X-ray Computed

Tomography (PET/CT) and SinglePhoton Emission Computed Tomography

(SPECT) imaging, has also been started.

The Group's environmental program

leads the community in low-level and

natural matrix material measurements and standardization, and continues to be heavily involved in the worldwide measurement of environmental-level

radionuclide dispersal and contamination

through a large number of international intercomparisons, traceability programs, and SRMs. A Radioanalytical Emergency

Procedures Manual Database has been

developed to assist organizations preparing

for emergency response.
34 NIST Physics Laboratory

ACCOMPLISHMENTS

New Approaches in Radionuclide Metrology

The NIST Triple-to-Double Coincidence

Ratio (TDCR) spectrometer has been

rebuilt and, as part of the testing phase, standard solutions of were measured

to assess its performance. An agreement

of 0.3 % between the TDCR and certified massic activities (activity per unit mass) was obtained without any attempt

to optimize the value of the ionization quench factor. As a second test, the TDCR was used in experiments leading

to the standardization of ""'Ni. Part of this study involved a direct comparison with Le Laboratoire National Henri Becquerel

(LNHB) using the same solution. The

NIST TDCR result for the massic activity was in excellent (0.3 %) agreement with

the value reported by LNHB, which used

three different TDCR spectrometers to obtain their result.

A short study involving measurements of

the electron capture nuclide ^'Fe was some- what less satisfying, with the NIST TDCR

and CIEMAT/NIST results agreeing only

to within 4 %, although no effort was made during these experiments to optimize the ionization quench factor. Despite

the lack of agreement in the experimental

results for '^Fe, a comparison of calculated

efficiencies as a function of the coincidence

ratio using NIST-developed software and

a program written at LNHB agreed to within 0.01 %.

Due to the complexity of the efficiency cal- culation arising from the need to account

for atomic rearrangements and competition between x-ray and Auger electron emission, a separate program needs to be

developed for each electron emitter being

studied. Programs are under development to analyze data from the decay of

the "'Ra decay chain, '^'^Ge/^'^Ga (mixed

electron capture, positron annihilation),

and the ^'°Pb decay chain (beta, conversion

electron, alpha). Experiments are currently

underway to standardize '"Sr/^^Y using

the TDCR spectrometer. Initial results indicate excellent agreement between the TDCR and CIEMAT/NIST.

Contact: Dr. Brian E. Zimmerman

[301] 975-4338

brian.zimmerman@nist.gov

Primary Standardization for a New SRM and International

Measurement Comparisons

A primary standardization of '^Fe by

isothermal microcalorimetry, initiated in 2004, was completed in 2006. Determinations of the activity for nuclides that decay by pure, low-Z (atomic number)

electron capture (EC) to the ground state of their daughters are amongst the most

difficult within the realm of radionuclidic

standardization. The present work on this difficult-to-measure nuclide is a return by NIST to the use of calorimetry for primary radionuclidic standardizations. While calorimetry was a classical radio- nuclidic measurement method used by

the NIST Radioactivity Group from the

early 1950s through 1975 for primary

standardizations, it was not used for the

past 30 years or so. In the past 5 years, calorimetry was used by NIST to perform

calibrations of brachytherapy sources of

«P '">St, and 'o^Pd. Figure 8. NIST TDCR system, open view showing the photomultiplier tubes.

A solid 30 GBq source of "Fe was pre- pared and gravimetrically linked to a ^^Fe master solution. The source was used to obtain an accurately determined power

measurement using the NIST dualcell isothermal calorimeter. The power

measurement was converted into a ^^Fe

activity through the use of a conventional

average energy per decay estimate. This

activity was linked to the master solution,

which had an assigned (^ = 1) uncertainty

of 0.39 %.

This standardization was used as the

basis for calibrating a new ^'Fe solution standard (SRM 4929F) as well as for measurements of a BIPM-distributed "Fe

solution that was part of an international measurement comparison. Although the

results on the international intercomparison are not yet compiled and released by the BIPM, the NIST results are in very good agreement with several other

national metrology laboratories.

Contact: Dr. Ronald Colle [301] 975-6149

ronald.colle@nist.gov

Standards for Medical Imaging

NIST has established a satellite facility at Oak Ridge National Laboratory (ORNL)

in Oak Ridge, Tennessee, to promote measurement accuracy for nuclear medicine imaging. NIST scientists will use the NIST/ORNL Nuclear Medicine Calibration Laboratory to prepare and measure

radioactivity standards used for Positron Emission Tomography (PET), a noninvasive technique that helps doctors diagnose

diseases (such as cancer), plan medical

treatment, and measure the efficacy of

therapies. An estimated one million PET

procedures were performed in 2004, a number expected to reach three million annually by 2010.
Ionizing Radiation Division 35

The NIST program needs to be carried out regionally because the short halflives of most PET radiopharmaceuticals

prevent shipment of standard test samples

over long distances. Radioactive '^F, for example, decays to half its total radioactivity in about two hours. Therefore, NIST is locating its satellite laboratories at key sites near manufacturers' distribution networks. The sites are selected based on location,

capability, and reputation.

ORNL has extensive expertise in radiation measurements, already operates a measure- ment traceability and testing program

with NIST, and is licensed and capable of

accepting, handling, and shipping radioactive materials. Initial calibrations of a '^F- FDG solution performed in May 2006 led

to the determination of a calibration factor

for dose calibrators as are used in the clinical setting. An intercomparison exercise is planned for the near future.

Figure 9. Typical phantom used in clinical quality assurance testing. The red sphere

inside the phantom is a NIST prototype

demonstrating how calibrated radioactive

inserts can be prepared.

Our close collaboration with the user community will lead to the development

of improved national standards to evaluate

the accuracy and precision of critical and

increasingly used medical diagnostic procedures. For example, we are developing

realistic and well-characterized phantoms

(models) of specific organs and other body parts for the evaluation and calibra- tion of whole body imaging technologies,

particularly those relying on the distribu- tion of radioactivity (such as PET). Our

work in developing a calibration for ""^Ge, which can be used as a longer lived radio- nuclide for PET instrument calibrations,

also contributes towards this goal. Such

developments will assure clinical reproducibility, the comparability of clinical results from different sites, and the correlation of measurements with biological parameters.

Contact: Mr. Jeffrey T. Cessna

[301] 975-5539

jeffrey.cessna@nist.gov

Emergency Preparedness for

Radiological Incidents

A survey of the national radionuclide

metrology community indicated a serious need for performance testing exercises

to assess the capability of laboratories to respond quickly to an unexpected release of radioactivity into the environment.

Radiological emergency response capabilities had previously focused on gross alpha and beta screening and gamma-ray

measurements. However, as the 2006

''"Po poisoning incident in the UK had

shown, having the capabilities to conduct

radioanalytical measurements for specific alpha- (and beta-) particle emitting radio- nuclides is also crucial.

The NRIP'06 emergency preparedness exercise resulted in radioanalytical measure- ment results reported within eight hours

of sample receipt for '»Sr, ^TMTh, "^U,

238U, 238p^^ 239pu^ ^^d ^'^'Am in urine,

soil, and water. Agreement of reported

radiochemical results with NIST certified values ranged from 1.4 % to 180 %.

While the results varied from laboratory

to laboratory and among radionuclides,

the information obtained by the participating laboratories will be helpful

for method improvement and improved

preparedness for radiological emergency

incidences.

The Group is also developing a Radioanalytical Emergency Procedures Manual

Database (REPMD) to assist organizations preparing for emergency response. This will collect existing procedures from

reliable sources into a guide to be accessed and searched by laboratories seeking ap- propriate methods for sampling, screening, surveying, and making rapid radioanalytical measurements of food, biological,

and environmental materials. A first-stage

prototype, demonstrating the ability to handle PDF documents describing

radioanalytical methods and to simplify

the method-collection process, has already

been delivered.

Contact: Dr. Jerome LaRosa

[301] 975-8333

jerome.larosa@nist.gov
Time and Frequency

Division

GOAL

To provide the foundation of

frequency measurements and

civil timekeeping for our Nation

The strategy of the Time and Frequency Division is to advance measurement

science and to provide time and frequency standards and measurement services to commerce, industry, and the public.

Thefirst strategic focus is

to develop the standards

that serve as reference for time and

frequency services and to research

advanced measurement systems.

TIME AND FREQUENCY

STANDARDS

INTENDED OUTCOME AND

BACKGROUND

The Time and Frequency Division maintains standards with the accuracy, continuity, and stabihty essential for supporting

U.S. commerce and scientific research; provides an official source of time for U.S.

civilian applications; and supports coordi- nation of international time and frequency

standards, including realization of the SI second.

NIST time and frequency standards are based on the NIST time scale and the NIST primary frequency standard, NISTF 1 . The time scale is an ensemble of five hydrogen masers and eight cesium-beam

clocks. The stability of the time scale is approximately 0.2 fs/s for thirty days of

averaging, with a long-term frequency

drift of less than 3 (fHz/Hz)/year. The

frequency of the time scale is calibrated by periodic comparisons to the NIST-Fl

laser-cooled cesium primary frequency

standard (9.2 GHz microwave frequency),

with a fractional frequency uncertainty Af/f

approaching 4 x

10"^" (0.4 fHz/Hz, as of

October 2007).

The NIST time scale is the basis of NIST's

realization of Coordinated Universal Time

(UTC), the international time scale. NIST

is one of about 60 timing laboratories

across the world continuously contribut- ing to the realization of UTC. Through

improvements to the NIST time scale, NIST's realization of UTC rarely differs from the international average by more

than 10 nanoseconds. In addition, NIST

is one of only seven laboratories worldwide

(as of late 2007) operating the highest accuracy primary frequency standards to determine the frequency (rate) of UTC.

The extraordinarily stable NIST time scale, coupled with world-leading performance

of the NIST primary frequency standard

(as of late 2007), provides U.S. industry

and science with a unique resource for the most demanding applications of accurate time and frequency. Fiowever, commercial

and scientific needs for even more accurate and stable time and frequency standards

drive a vigorous NIST research program

to improve microwave frequency standards and to develop new, optical frequency

standards.

Since the first atomic clock was invented at the National Bureau of Standards (NIST's

predecessor) in 1949, the performance of

primary frequency standards has consistently improved by about a factor of ten each decade—driven by, and enabling, advances such as telecommunications

synchronization and the Global Position- ing System (GPS). NIST research on

microwave and optical frequency standards

strives to at least maintain this rate of

performance improvement.
Time and Frequency Division 37

ACCOMPLISHMENTS

Primary Frequency Standards

The NIST-Fl laser-cooled, cesium fountain primary frequency standard (Fig. 1) is the U.S. national standard for frequency

and the realization of the SI second.

Since the first formal report of NIST-Fl

frequency to the International Bureau of

Weights and Measures (BIPM) in 1999,

the NIST-Fl uncertainty has been reduced

by about a factor of four.

© Geoffrey Wheeler

Figure I.The NIST-F1 cesium-fountain primary frequency standard, tine Nation's standard for frequency and the SI second,

NIST-F 1 frequency evaluations reported

to BIPM in 2007 included an "in-house"

fractional frequency uncertainty of ap- proximately 4 x 10"^ (0.4 fHz/Hz),

increasing to about 8 x 10"" (0.8 fFiz/Hz)

as received at BIPM due to uncertainties

in the satellite-transfer process. Both of

these results were the best ever reported to BIPM. NIST-Fl has for several years been

the world s best performing primary fre- quency standard, continuing to lead as the performance of both NIST-Fl and other

standards across the world improves.

While continuing to optimize NIST-F 1 , the Division is actively developing the next-generation primary fi-equency standard, NISTF2. The ultimate goal for NIST-F2 is to approach an "in-house" fractional frequency

uncertainty of 1 x 10 '^ in the next few years.

NIST-F2 will use a multi-toss, multiple-velocity system, in which about ten low-density atom balls will be launched to different heights in rapid succession, all coalescing

in the detection zone without having

crossed paths in the Ramsey interroga- tion region. This approach will minimize

spin-exchange shifts while still providing

sufficient atom numbers at detection for good stability.

The second major improvement in NISTF2 will be to cool the drift tube and inter- rogation regions to cryogenic temperatures, vastly reducing the blackbody shift. Use of different cryogens, and/or pumping

on the cryogens, will also enable accurate measurement of the blackbody shift, the value of which has been the subject of

intense debate.

Contact: Dr. Steve Jefferts [303] 497-7377

steven.jefferts@nist.gov

Research on Optical Frequency

Standards

The ultimate accuracy limit of cesium

microwave standards, which operate near

10'° Hz, is expected to be on the order of

10'"' Hz/Hz (their fractional frequency

uncertainty). Optical frequency standards,

operating on the order of 10" Hz, have the

potential for substantially greater stability

and accuracy. Optical frequency standards

also have a potential for dissemination

through optical fiber, which may be ad- vantageous in many applications. As of late 2007, several Division optical frequency

standards are performing with fractional frequency uncertainties on a scale of

10"'^ Hz/Hz, with rapid progress continuing toward the expected achievement of

fractional frequency uncertainties in the

10'"* Hz/Hz range.

The Division conducts a vigorous research program on prospective optical frequency

standards, simultaneously pursuing several

different approaches. These include cold, trapped single ions; cold, neutral atom

clouds; and "logic clocks," using tech- niques of quantum information processing. A crucial part of optical clock research

is optical frequency synthesis using femto- second laser frequency combs, described in

a later section.

There are several reasons for studying

multiple systems. It is too soon to predict

which optical standard will have the lowest overall uncertainty during a period of

particular rapid progress; having multiple

standards using different species and

techniques enables intercomparisons that

reveal unforeseen uncertainties; different standards show promise for different applications such as higher stability or lower

ultimate uncertainty, just as hydrogen

masers display greatest stability and cesium

fountains lowest uncertainty among current microwave standards; and comparing

different frequency standards is a sensitive probe of fundamental physics, such

as possible time variation in fundamental

constants.

Mercury-Ion Optical Frequency

Standard

A frequency standard based on optical transitions (282 nm, 1064.7 THz) in a single,

laser-cooled, trapped mercury ion has potential for better accuracy than cesium fountain standards by a factor of 100 or more. With a Q factor > 10''* and a transition that

is relatively insensitive to environmental

factors, the potential fractional frequency

uncertainty Aflfiox a mercury ion standard

is as small as 10 '** Hz/Hz.
38 NIST Physics Laboratory

As of late 2007, continuing imptovements

in the mercury ion standard have reduced

the fractional frequency uncertainty to

1.6 X 10"'^ Hz/Hz—the world's best result so far for any frequency standard. This

result is about 25 times better than the current NIST-Fl performance. However,

frequency is defined by a microwave

transition in cesium, so no standard based on another oscillator can have a smaller absolute frequency uncertainty. (As further improvements are developed, there may

ultimately be an international redefinition of frequency.)

For several years, NIST has been conducting intercomparisons between NIST-Fl,

the mercury-ion clock, and other optical

frequency standards. Measurements are referenced to NIST-Fl through a hydrogen

maser, using a femtosecond-laser frequency

comb to compare optical and microwave

frequencies. Such experiments demonstrate the frequency stability of the optical

standards. They also set a limit on possible

variations of fundamental constants related

to the fine-structure constant a, in particular the possible temporal variation of the quantity g^^ ( I m^^ ) a^.

Assuming any variation is due to a only, the most recent NIST result (early 2007)

sets an upper bound for the fractional change in the fine-structure constant as no greater than 1.3 x 10'"' per year. It

is a tighter bound by about a factor of

300 than astronomical observations that suggested variations in the fine-structure constant over periods comparable to the age of the universe, and better by a factor of 20 compared to previous measurements

based on frequency standards.

Contact: Dr. Jim Bergquist

[303] 497-5459

james.bergquist@nist.gov

"Logic Clock" Optical Frequency

Standard

A new type of optical frequency standard

uses quantum-information (QI) tech- niques to exploit previously inaccessible clock transitions. The aluminum ion has

a very narrow, doubly forbidden transi- tion at 267 nm that is highly promising

for a precise optical frequency standard. However, the aluminum-ion laser-cooling

transition at 167 nm is not accessible with

current laser technology. The logic clock

navigates around this barrier by using a beryllium ion and an aluminum ion in tandem. Laser operations on the beryllium

ion—the workhorse of the trapped-ion

QI program—cool and interrogate the aluminum ion.

© Geoffrey Wheeler

Figure 2. Till Rosenband adjusts the "logic clock," an optical frequency standard based on quantum information processing

techniques.

Even in early-stage development, the aluminum-ion logic clock has relative

uncertainties approaching 2 x 10 " Hz/

Hz, with significant improvement likely. This approach can be applied to nearly any

ion, opening up a wide range of potential

frequency standards that were previously

unavailable.

Contact: Mr. Till Rosenband

[303] 497-4293

till.rosenband@nist.gov

Neutral Atom Optical Frequency

Standards

The Division develops optical frequency

standards based on clouds of cold neutral calcium atoms and lattices of cold ytter- bium atoms. The calcium optical standard, based on a 657 nm (456 THz) transition,

is particularly robust and well suited as a frequency reference ("flywheel ") for inter- comparisons of optical standards.

Division scientists have constructed a simple, robust, and potentially transportable version of the calcium optical standard,

requiring less than 15 minutes warm-up

time and remaining locked with no inter- vention for 10 or more hours. The calcium

standard achieves a short-term fractional frequency stability of 2 x 10 '^ Hz/Hz with one second of averaging and 3 x 10'"' Hz/

Hz for 200 seconds.

The Division recently demonstrated an

optical standard based on neutral ytter- bium atoms confined to a lattice, produced

by the electromagnetic potential wells of

standing laser beams. The lattice confines

ultracold atoms to small spatial areas, enabling high signal-to-noise ratios while

suppressing motion-related efi-ects such

as Doppler shifts and cold collisions. The

ytterbium lattice is the first example of

using even-numbered nuclei ('^''Yb) with a

strictly forbidden 'S^ - ^P^, clock transition. A small, external magnetic field provides

enough dipole mixing to enable the transition, one insensitive to AC Stark shifts.

The "^*Yb lattice standard demonstrates a

fractional frequency stability of order 10''^ Hz/Hz in early testing, with substantial improvements expected in the near future.

Contact: Dr. Chris Gates

[303] 497-7654

chris.oates@nist.gov
Time and Frequency Division 39

Thesecond strategic focus

is to develop and operate

the frequency and time services

essential for synchronizing important

industrial/commercial operations and

supporting trade and commerce.

TIME AND FREQUENCY

SERVICES

INTENDED OUTCOME AND

BACKGROUND

The Division provides continuous, reliable, time and frequency signals in a wide variety of formats and accuracies to meet diverse needs of U.S. industry, trade, science, and

the general public. NIST time and frequency information is distributed over the Internet, by radio broadcasts, over telephone lines, and through satellites to serve customers in

finance, telecommunications, science, trans- ponation, radio/TV broadcasting, and other

businesses—and as a reliable and convenient

source of official U.S. time for the general

public.

NIST radio stations WWin Ft. CoUins,

Colorado and WWVH in Kauai, Hawaii

broadcast shortwave radio signals containing

a rich variety of time and frequency information, in the form of verbal announcements,

tones, and digital time codes. NIST radio

station WWVB in Ft. Collins, Colorado

broadcasts a low-frequency (60 kHz) digital time code that automatically sets consumer

timepieces to official U.S. time and date, automatically correcting for daylight saving

time, leap years, and leap seconds.

NIST's most heavily used service is the Inter- net Time Service (ITS), automatically setting

clocks in computers and networked devices

to NIST time. The Division also provides the modem-based Automated Computer Time

Service (ACTS) to set computer and network

device time. Many ACTS customers need

the security of a direct connection to NIST

to ensure that the time is legally traceable

to NIST and is auditable. For example, the National Association of Securities Dealers (NASD) requires its 600,000 members to time-stamp many billions of dollars of electronic transactions each business day against

NIST time.

The Frequency Measurement and Analysis

Service (FMAS) and the Time Measurement

and Analysis Service (TMAS) serve industrial and research customers who need tight

traceability to NIST time and frequency

standards. These customers receive continuous, real-time NIST traceability through a highly automated system remotely monitored by NIST, receiving NIST standards by

comparison to GPS broadcasts. The Division

has developed similar technology to enable coordination of time scales among nine national timing laboratories in North America,

Central America, and South America, with

additional laboratories scheduled to join

the network in fiiture years. The low-cost,

user-friendly systems allow laboratories with

limited technical and financial resources to synchronize their time scales to low uncertainties previously available only to the most

advanced timing centers.

To enhance U.S. expertise in this field, the Division offers a variety of training courses. A

four-day metrology seminar with more than 20 expert instructors is offered annually, a new three-day seminar has been initiated for

entry-level time and frequency metrologists,

and we cosponsor an annual workshop on

synchronization in telecommunications systems. NIST staff members also teach about 20 courses per year on special topics in time

and frequency measurement at conferences and on-site at NIST.

ACCOMPLISHMENTS

NIST Internet Time Service (ITS)

Fourteen ITS servers at eleven locations

across the Nation respond to more than two

billion requests per day (as of late 2007)

for setting computer and network clocks to NIST time, automatically. (See Fig. 3.) The

Division website provides free client soft- ware, complete source code, and complete

instructions (about 100,000 downloads

per month). Automatic synchronization to ITS is now a capability of the most popular

computer operating systems, including the

latest versions of Windows, Mac OS, and

many commercial versions of Linux.

Figure 3. Growth in use of the NIST Internet Time Service.

The Division continually updates the servers, software, and network infrastructure, working with the NIST networking group,

to ensure continued provision of ITS in

light of increasing demands.

A number of companies have partnered

with NIST to add traceability and auditability to ITS for timestamping electronic documents and financial transactions. These

applications are in rather limited use now,

but are growing rapidly.

Contact: Dr. Judah Levine

[303] 497-3903

judah.levine@nist.gov
40 NIST Physics Laboratory

NIST Radio Stations WWV,

WWVH, and WWVB

The Division continues to upgrade the

radio stations as part of a long-term modernization plan. Progress includes continuing improvements to WWV and WWVB

transmitters and broadcast systems, includ- ing systems to ensure automatic recovery from power failures or loss of primary

transmitters, replacement of WWVH (Hawaii) metal antenna towers with fiberglass towers to eliminate corrosion damage, and

upgrading insulators in the guy wires sup- porting the eight 122 m (400 ft) towers for the WWVB antennas (Fig. 4).

© Photo Works, Louisville, Colorado

Figure 4. An aerial view of the WWVB

antenna systems.

More than 50 manufacturers produce

WWVB-controlled timepieces, with

several million new units sold each year. With growing sales, both manufacturers and consumers want to know that WWVB

signal strength is sufficiently strong across the Nation to ensure good reception. We

designed monitors to measure power from

WWVB broadcasts, which we plan to place at strategic locations around the U.S. Each will continuously report the WWVB

signal strength to the Division through

the Internet. The results will be displayed on a publicly available website, along with

archives of all signal strength records. These data will help manufacturers set performance specifications for real-world

signal strengths.

We have been actively consulting

with WWVB-controlled timepiece

manufacturers to improve their product

performance. Based on experiments

conducted with manufacturers, we

modified the modulation depth of the time code broadcasts to provide more

reliable performance for radio-controlled timepieces in noisy environments. Also, the Division published Recommended

Practices for Manufacturers and Consumers ofWWVB Radio Controlled Clocks after consultation with manufacturers and

enthusiast user groups. It has been

downloaded more than 200,000 times in the past two years.

Contact: Mr. John P. Lowe

[303] 497-5453

john.lowe@nist.gav

Ihe third strategic focus is to

develop new measurement

systems and methods in support of

emerging technologies.

NEW MEASUREMENT

SYSTEMS AND METHODS

INTENDED OUTCGME AND

BACKGROUND

In addition to meeting current customer

needs, the Division prepares for the fiature of time and frequency measurements and

calibrations. Through interactions and

discussions with constituents, we identify

important emerging requirements and

technologies. We strive to apply our expertise and creativity to those applications with

the potential for greatest impact on U.S.

industry, science, and the general public.

Synthesis and measurement of optical

frequencies is crucial to the future of Division programs, and time and frequency

metrology in general. Division expertise in developing and applying frequency combs

based on femtosecond lasers has led to measurement of frequencies with relative uncertainties approaching 10 ''' (0.1 aHz/

Hz), orders of magnitude better than pre- viously possible, and to direct comparison

of microwave and optical frequency stan- dards, bridging five decades in frequency.

We are working on techniques for amplification, noise reduction, and applications

across different frequency ranges, such as the important near-infrared telecommunications range.

A second key thrust is development of new

tools to better measure close-to-carrier noise in oscillators and other electronic components. Such measurements are

crucial to development of new oscillators, microwave and optical, used in advanced

radars, telecommunications, high-speed

digital circuits, and many other applications. Much of this work is conducted

with significant support from DARPA,

involving NIST, industry, and research organizations.

A third major program is the development of ultra-miniature atomic frequency

standards and related devices, to dramatically improve the performance of small

electronic devices such as GPS receivers, portable magnetometers, and gyroscopes. Such chip-scale atomic devices need not

be as accurate or stable as large laboratory

standards, but they will bring atomically

precise measurement and frequency control to small, battery-powered electronic

devices.

DARPA and other funding agencies

support the Division's participation in government-industry-university collaborations, recognizing that our core expertise

in research and metrology accelerates the
Time and Frequency Division 41

development of commercial and military

products and services with strategic national economic and security impacts. This support is one important way the Division

ensures that programs are well aligned with

high-priority industrial and national needs.

ACCOMPLISHMENTS

Improvements in Frequency

Combs

A key application of frequency combs

based on femtosecond lasers is to generate an arbitrary optical or microwave fre- quency output given an optical frequency

reference input. This remarkable capability is crucial to the development and

dissemination of useful optical frequency

standards. As mentioned, the Division

uses optical frequency combs to directly

compare a wide range of microwave and

optical frequency standards, includ- ing NIST F-1 (9.2 GHz), the calcium

atom standard (456 THz), the mercury

ion standard (doubled 532 THz), the aluminum ion "logic clock" (doubled

562 THz), the ytterbium lattice clock (519 THz), and the strontium atom clock atJILA (430 THz).

The Division has been continually improving the performance and versatility of

frequency combs by exploring new ways

to broaden the femtosecond laser output

without use of microstructured optical

fibers, which are susceptible to damage.

The Division also collaborates with the NIST Electronics and Electrical Engineering Laboratory to develop near-infrared femtosecond lasers for improved wavelength and frequency references, such as

in the important 1.4 pm to 1.6 pm optical telecommunications band.

comb-generation techniques: broadband

operation and nonlinear microstructure

fiber. The frequency differences, deter- mined by optical heterodyne techniques, were measured to a relative uncertainty of

1.4 X

10"'-' Hz/Hz, with the uncertainty

arising primarily from mechanical and

thermal effects and limits on integration

time. The results suggest optical frequency

combs can be reliably used for frequency

comparisons and synthesis to at least a

fractional uncertainty of 10 " Hz/Hz,

and likely better when technical noise (mechanical and thermal fluctuations) are better controlled and longer integration

times are used.

Recent Division advances in frequency

comb development and applications include techniques for high-resolution,

two-dimensional dispersion of the modes

of the comb, into a "frequency brush."

(See Fig. 5.) This enables rapid, high-resolution spectral fingerprinting—high-resolution absorption spectroscopy of iodine vapor spanning 6 THz can be collected

in a few milliseconds. This technique is promising for high-resolution quantum

coherent quantum control and arbitrary

optical waveform synthesis, areas the Division is actively pursuing.

The Division also demonstrated the use of frequency combs for ultraprecise time

and frequency transfer over fiber optic

networks, including a "real world" demonstration of time transfer over 30 km

of optical fiber in an urban environment

with a timing jitter better than 10 '^ Hz/

Hz at 1 second of integration. Such exquisite performance will enable the power

of future optical frequency standards to be efficiently transferred and applied.

Contact: Dr. Scott A. Diddams

(303) 497-7459

scott.diddamsOnist.gov

© Geoffrey Wheeler

320 GHz

Figure 5. Tara Fortier adjusts an optical

frequency comb, and a "frequency brush,

dispersed modes of the frequency comb

used for massively parallel absorption

spectroscopy of iodine.

Figure 6. Scott Diddams with a femtosecondlaser-based

optical frequency

synthesizer system.

The Division led an intercomparison of

four different femtosecond-laser frequency combs from three different laboratories, using two fundamentally different
42 NIST Physics Laboratory

Chip-Scale Atomic Devices

The Division has become a world leader

in research, metrology, and development

of chip-scale atomic devices (CSADs),

bringing atomically precise measurements

to portable electronic applications, such as timekeeping and frequency control, measurement of magnetic fields, and inertial navigation (gyroscopes).

The program began with development of a miniature, all-optical atomic clock, based on coherent population trapping. This stimulated DARPA interest in further de- veloping a chip-scale atomic clock (CSAC)

to bring atomically precise timing and

frequency control to portable electronic

devices, such as enhanced GPS receivers and more secure communications devices. The goal is to develop a CSAC of 1 cm'

total volume, consuming no more than 30 mW of power with a fractional fre- quency stability of about 1 X 10 " Hz/Hz

over one hour. This has now moved into a commercialization phase in which NIST

assists with evaluations.

The Division has expanded the basic chipscale atomic technology into other types of

instruments. Atomic magnetometers, for example, have been developed with physics

packages of similar size to the CSACs.

Measurements indicate that the sensitivity of these instruments can be as good as 70 fr/Hz'-, which compares favorably with

magnetometers based on high- T super- conducting quantum interference devices (SQUIDs)—but without the need for cryogenic cooling, large electronics packages, and the power they require.

Highly sensitive gyroscopes are under

development with the same power and size

goals as the clocks and magnetometers.

These inertial sensors are based on polarized atomic nuclei that define a direction

in space as a reference for precision measure of rotation.

The Division has collaborated with the NIST Electronics and Electrical Engineering Laboratory to use standard MEMS

fabrication techniques in making the CSAD physics packages, suggesting that chip-scale atomic devices based on the Division model could be mass-produced

at relatively low cost using wafer-level as- sembly techniques. Such a process would

enable the extremely broad application of

CSADs. The Division continues to actively

partner with companies and research or- ganizations to help commercialize CSADs

and to develop new applications.

Contact: Dr. John Kitching

(303) 497-4083

john.kitchingOnist.gov

Figure 7. Photomicrograph of the physics

package of a NIST chip-scale atomic magnetometer [CSAM], with a schematic

diagram. [1 ] Laser [2] Optics. [3] Vapor cell with rubidium atoms. [4] Detector For scale, a CSAM is shown next to a dime and rice grain.

Thefourth strategic focus

is to develop quantumlogic components and quantum

information systems based on

trapped ions, in support of new

atomic frequency standards and a

national program aimed at advancing

computation and communication.

QUANTUM

INFORMATION

PROCESSING USING

TRAPPED IONS

INTENDED OUTCOME AND

BACKGROUND

We conduct research on the development

and properties of prototype quantumlogic devices consisting of small numbers of electromagnetically trapped and

laser-cooled ions serving as quantum bits

(qubits). This research comprises quan- tum computing, quantum measurement

(including noise reduction in frequency

standards), and development of new

classes of quantum-logic-based frequency

standards.

This project arose as part of a long-term

research program on ion-based frequency

standards. In particular, the goal of reducing fundamental quantum projection noise suggested the possibility of using similar approaches for quantum computing and

quantum metrology. Division researchers soon became leaders in quantum computing research, and NIST-wide programs

in quantum computing and quantum
Time and Frequency Division 43

communications rapidly developed and

demonstrated significant success.

Our focus on quantum computing meets two primary needs. First, quantum computing research is a national priority to ensure economic and physical security, with

substantial investment by both defense and civilian fianding agencies. Our unique

expertise in quantum state engineering has made the trapped-ion quantum computing

program a world-leading effort.

Second, Division work on quantum state engineering serves our time and frequency

metrology mission. The "logic clock" optical frequency standard described earlier is an excellent example of quantum information processing techniques being applied to develop a new type of atomic clock, which

is already performing comparably to the

world's best optical frequency standards.

It can, in principle, be adapted to other

species that hold potential for even better performance. The Division has also demonstrated Heisenberg-limited spectroscopy

with three entangled ions, in a scheme that could be scaled to an arbitrary number

of ions or atoms. In principle, this could

dramatically reduce the averaging time re- quired for a frequency standard to reach its

statistical uncertainty limit, substantially

improving the performance, and broadening the applications, of atomic clocks.

ACCOMPLISHMENTS

Progress in Quantum State

Manipulation for Quantum

Computing and Quantum

Measurement

The Division's quantum computing and

quantum measurement program continues

to make strong progress. We have now

demonstrated all the so-called DiVincenzo

criteria for a practical, scalable quantum

computer, although of course much

additional research and development is required before a practical quantum computer is realized.

In the past several years. Division scientists have demonstrated for the first time

deterministic teleportation of quantum

information on atomic (ionic) qubits

paving the way for efficient transfer of in- formation in a complex quantum computer—and robust quantum error correction schemes necessary for practical, scalable quantum computers. Division scientists achieved a world record of entangling six beryllium ions in a Schrodinger cat state

general considered the most useful and most highly entangled state for quantum

information processing.

More recently the Division has demonstrated semi-classical quantum Fourier transform operations on an array of three trapped beryllium ions. Performing

Fourier transform operations is a key step towards realizing Shor's algorithm in a

scalable quantum computer, a method to quickly factor large integers for quantum

cryptography.

The Division has demonstrated worldleading coherence times of greater than

10 seconds for single physical qubit states, orders of magnitude greater than previ- ous experiments, and orders of magnitude

greater than the typical microsecondorder operation times. In principle this enables many thousands of operations to be performed without loss of coherence. And the Division demonstrated the first

successful experimental purification of

two-ion entangled states, overcoming the

effects of decoherence when one qubit in an entangled pair is physically transported

to another location.

© Geoffrey Wheeler

Filter Capacitor Microfabricated Control Lead

Filter Resistor

Figure 8. David Wineland adjusting one of the systems used for studying quantum-logic

gates, and a new planar electrode ion trap

for scalable quantum computing research.

A major challenge for developing a largescale quantum computer based on trapped

ions is to develop an architecture that can

simultaneously handle a large number

of ion qubits, including laser cooling,

quantum processing operations, storage and transport of qubits throughout the computer, and other operations. Recently, the Division has demonstrated a planar

geometry for ion traps, where the previous

three-dimensional array of electrodes has been "unfolded" into a planar array that

still generates an electromagnetic potential

well to trap and move the ion qubits. This new planar geometry is highly promising

for a practical, scalable solution.

Contact; Dr. David J. Wineland

(303] 497-5286

david.winelandOnist.gov
Quantum Physics

Division

GOAL

To make transformational

advances at the frontiers of

science, in partnership with the

University of Colorado at JILA

The strategy of the Quantum Physics Division is to help produce the next generation of scientists and to investigate new ways ofprecisely directing and

controlling light, atoms, and molecules; measuring electronic, chemical, and

biological processes at the nanoscale; and manipulating ultrashort light pulses.

Thefirst strategic element is to

develop measurement science

tools and applications.

MEASUREMENT SCIENCE

INTENDED GUTCGME AND

BACKGROUND

Measurement science is used for many

industrial and scientific purposes and is

central to many NIST activities. Applications range fi-om providing the length scale

for mechanical measurements to providing a

direct connection between optical and radio

frequencies. The Quantum Physics Division continues a leadership role in developing new precision-measurement techniques and

applications.

The highly stabilized laser is the workhorse

in precision measurement. Traditionally, this meant continuous wave (CW) lasers that generate light with a very precise and stable

single frequency. Recently, the Division became an international leader in adapting CW techniques to the stabilization of

mode-locked lasers, which generate a broad

comb composed of sharp lines, each of

which has a veiy precise and stable frequency. Such a stable frequency comb not only

simplifies measurement at any given optical

frequency, but also facilitates establishing a

direct connection between optical and radio

frequencies. This connection, in turn, enables optical atomic clocks and absolute optical frequency metrology. The importance

of femtosecond (10'^ s) comb techniques,

and the Division's contributions to them, was recognized by the 2005 Nobel Prize in

Physics, shared by long-time Division member and JILA pioneer John L. Hall.

Applying precision optical spectroscopic

techniques to help improve our understanding of molecular interactions is also proving

fruitftil. They can also be used for address- ing fundamental physical problems, such

as determining the electron electric dipole

moment.

These developments continue JILA's tradition of developing laser stabilization and

associated precision measurement methods

used today by NIST the international stan- dards community, and leading universities worldwide. Our strong position in this new

field assures NIST's continued leadership in standards and measurement.

ACCOMPLISHMENTS

Electron Electric Dipole

Measurement

The so-called Standard Model of particle

physics is enormously successfial in predicting the behavior of the zoo of subatomic

particles that make up the world around

us. However, it can be shown mathematically that this model cannot explain what

happens to particles that collide at very high energies, nor can it describe the high-temperature conditions that must

have been present at the very earliest moments after the big bang. It is not possible

to build an accelerator big enough to reconstruct those conditions, but theorists point out that the speculative models they

construct to explain the highest energy

physics also make predictions about the

properties of everyday, room temperature

particles, predictions that can be tested in a

precision measurement lab.

One such prediction is that the electron should have a nonzero electric dipole

moment (EDM). The assertion is that the

electron possesses a tiny asymmetry such

that its center-of-mass and its center-of- charge will be offset from one another. If the current experimental limit on this off-
Quantum Physics Division 45

set could be improved by a factor of 100,

a large class of proposed extensions to the Standard Model could be either disproved

or else provided with their first experimental support.

The experiment is daunting: the current experimental limit says the offset is smaller than 10 '^ femtometers. Put another way,

if you were to scale the electron up to the

size of the earth, its asymmetry would be

smaller than a wavelength of light.

To go another two orders of magnitude

further. Division scientists are making use of cold, trapped molecular ions to serve as

high-electric-field laboratories for studying

electrons. They are probing the electron- in-a-molecule system with a combination

of frequency-comb-enabled optical spec- troscopy and atomic-clock-driven radio- frequency spectroscopy.

Contact: Dr. Eric Cornell [303] 492-6281

cornell@jila.colorado.edu

Figure 1 . The Quantum Physics Division's newest hire, James Thompson.

Optical Atomic Clocks

An optical atomic clock uses an optical fre- quency transition as its quantum reference, giving it better frequency stability than

a clock using the standard microwavefrequency transition. An optical clock produces a phase-coherent RF signal from

the optical standard by using an optical

frequency comb that is precisely phase

stabilized to the optical standard.

An optical atomic clock based on ultracold strontium atoms confined in an optical

lattice has demonstrated a world-record

spectral resolution, reaching a resonance

quality factor of 2.4 x lO'''. The fractional frequency instability has already reached

3 fHz/Hz at 1 s. We have characterized the systematic uncertainty in fractional frequency to 0.15 fHz/Hz, which has sur- passed the current best evaluations of the NIST cesium primary fountain standard. Future progress on this atomic clock is expected to be as fruitful as in the past. We expect to push this system to an ac- curacy level reaching 0.01 fHz/Hz and

instability lower than 1 fHz/Hz at 1 s.

The stability of such a clock can be evalu- ated only through comparison to another

high-stability optical clock. Ideally, comparison to a third clock is needed to deter- mine the performance of all of the clocks involved. The need for comparison has hindered atomic clock development because

the timing/frequency signals are degraded

by transmission. Recent efforts at JILA and

NIST have demonstrated coherent optical

phase transfer over a 32 km optical fiber with fractional frequency instability of

0.01 fHz/Hz at 1 s.

This work constitutes a major advance in the ability to distribute extremely precise

and accurate frequency and timing signals over long distances through fiber networks.

In fact, we have recently taken advantage

of this capability to remotely compare

the Sr lattice clock at JILA against the Ca

optical clock in the Time and Frequency

Division at NIST. The short-term stability

of the Ca clock permitted the evaluation of

the overall systematic uncertainty of the Sr clock at the level of 0.15 fHz/Hz.

These fiber stabilization results are a twoorders-of-magnitude improvement in the

stability of frequency distribution, and

demonstrate the lowest level of timing jitter and phase noise for a tens of kilometer

long-distance timing distribution system. This technology will be extremely valuable

for particle accelerator facilities, synchronized radio or optical telescope arrays, remote calibration of length standards, and

long-distance interferomerry.

Contact: Dr. Jun Ye

[303] 735-3171

ye@jila.colorado.edu

Fundamental Limits to

Femtosecond Combs

Femtosecond optical frequency combs generated by mode-locked lasers have revolu- tionized optical frequency metrology and

enabled optical atomic clocks. Measure- ments have shown that the intrinsic stability of femtosecond combs is remarkable,

better than 10 Hz/Hz.

At some level, quantum fluctuations will

set a lower limit for the stability, in a manner analogous to the well-known Schawlow-Townes linewidth of a CW laser. Just

as for the Schawlow-Townes linewidth, some photons spontaneously emitted by

the gain medium will be incorporated into

the lasing mode, but they will have the wrong phase, timing, and wavelength. A

mode-locked laser is intrinsically a nonlinear system, thus the analysis is much more

complex than for a CW laser, although

there are similarities to noise processes in an amplified fiber optic telecommunications system.

Accurate calculation of the effect of quan- tum fluctuations on a mode-locked laser

requires a good understanding of the laser's dynamic response to a small perturbation. We have experimentally characterized the dynamics by recording how the

pulse energy, center frequency, phase, and

timing respond to small changes in pump

power. The measurements showed that gain dynamics, which had been neglected
46 NIST Physics Laboratory

previously, must also be included. The

full characterization is now being used to predict the phase fluctuations driven by

spontaneously emitted photons.

Contact: Dr. Steven T. Cundiff

[303] 492-7858

cundiffs@jila.colorado.edu

Thesecond strategic element

is to exploit Bose-Einstein

condensation, quantum degenerate

Fermi gases, and cold molecules for

metrology and ultralow-temperature

physics.

ULTRACOLD ATOMS AND

MOLECULES

INTENDED GUTCGME AND

BACKGROUND

The Quantum Physics Division and

JILA are world renown for studies of

Bose-Einstein condensates and quantum

degenerate Fermi gases. The exemplary

JILA collaboration between NIST and

the University of Colorado (CU) led to the achievement of the first Bose-Einstein

condensate by Eric Cornell (NIST) and

Carl Wieman (CU), who together received the 2001 Nobel Prize in Physics. This

achievement, coupled with the creation of the first quantum degenerate Fermi gas and the first Fermi condensate by MacArthur Fellow Deborah Jin (NIST), places the Quantum Physics Division and JILA

at the forefront of studies of macroscopic

quantum mechanical systems.

A better understanding of these systems is

critical as the miniaturization of electronic components pushes into the size region

where quantum mechanical effects play

a significant role in their operation. Additionally, these systems provide unique

opportunities for metrology and for gaining insights into analogous transitions

in technologically important solid-state systems. We plan to continue to explore

the new quantum mechanical systems that these discoveries have made accessible and

to maintain our leadership position. The

development of techniques to produce ul- tracold molecules also promises important

advances in chemical physics.

ACCOMPLISHMENTS

Casimir-Polder Forces

When two solid objects are brought very

close together but not quite into physical

contact, they experience a mutual attraction

called the Casimir force. WTiile this force is very small by most measures, it has technological significance because in nanoscale mechanical devices, the force can dominate the

behavior. Generated by quantum mechanical fluctuations in the vacuum separating

the two objects, the Casimir force has long

been predicted to depend on temperature,

although this dependence has never been

conclusively demonstrated.

Division scientists have been studying an

effect that is simpler than, but related to, the Casimir force—the Casmir-Polder

force. This force between a solid surface and a nearby atom is so small that it is most

readily studied using an ultracold sample of

atoms, a Bose-Einstein condensate (BEC).

Figure 2. The ultrahigh vacuum chamber

used for Casimir force measurements.

Division scientists have recently succeeded

in observing for the first time the temperature dependence of a Casimir-type force. A BEC of rubidium atoms was suspended

magnetically about 6 ]im above a surface of

fused quartz. Then, as the surface temperature was increased from 300 K to 570 K,

the attractive pull on the BEC was seen to more than double.

Contact: Dr. Eric Cornell (303)492-6281

corneiiOjiia.colorado.edu

Kosterlitz-Thouless Transition on a Lattice

The nature of a phase transition (such as melting, ferromagnetism, superconductivity, or superfluidity) can be strongly

affected by the dimensionality of the

system. For instance, it's widely believed

that high- superconductivity is at least in part a consequence of the two-dimensional

nature of the layered structure of copper

oxide crystals. In gases of ultracold atoms,

the now familiar Bose-Einstein phase transition (between a normal and a superfluid

gas) that occurs in three dimensions is pre- dicted to be suppressed in two dimensions

in favor of a more exotic transition known

as the Berezinskii-Kosterlitz-Thouiless (BKT) transition.

Division scientists have been studying

BKT physics in a system of ultracold rubidium atoms confined in a two-
Quantum Physics Division 47

Figure 3. Top view of a quasi-2D Bose-Einstein condensate as the effective temperature

gradually increases from left to right. The randomly ordered dots that appear at higher

temperature are the cores of thermally generated vortices and are thie signature of a

Berezinskii-Kosterlitz-Thouless transition.

dimensional optical lattice. Atoms can move from one well of the lattice only

by tunneling; atoms within each well make up a conventional, if small, 3-D

BEC, with a well-defined quantum phase.

Initially, the phases in all the wells are the same; the phase coherence of the system

extends across the entire sample. As the temperature is increased, thermally driven phase fluctuations increase and eventually

pairs of vortices are spawned and wander

randomly through the sample, destroying the phase coherent state. The sudden

appearance of vortices is the microscopic

mechanism for the BKT transition. While

the BKT transition has been studied in other condensed-matter systems, this is the

first time the appearance of vortices has been quantitatively documented.

Contact: Dr. Eric Cornell (303) 492-6281

cornell@jila.colorado.edu

Ultracold Fermions and

Superfluidity

Several studies of the behavior of Fermi

condensates in the region of the BCS-BEC

crossover have been completed. Working with condensed matter theorists with

expertise in high- T superconductivity, the measured phase diagram for Fermi superfluidity was compared with a BCS-BEC

crossover theory. While the good qualitative agreement seen in this comparison is very encouraging, quantitative difi^erences

reveal the need for more advanced theoretical understanding of the crossover.

0.0 ' ' • ^ 1

1 0 -1 Interaction Strength Mk^a

Figure 4. Measured Fermi superfluid phase

diagram compared with BCS-BEC crossover

theory (red line).

We have also quantitatively studied the thermodynamics of the Fermi gas in the region of the BCS-BEC crossover. We

measured the momentum distribution of the Fermi gas, which shows dramatic

effects due to the pairing of atoms. We also measured the energy of the gas at unitarity (strongest possible interactions). This measurement demonstrated that ultracold Fermi gases are in the regime of "universality," where the physics does not depend on

the details of the interatomic potentials.

In related work, a new experimental probe

of the gas was introduced by demonstrating that information can be extracted from noise in absorption images of the

ultracold cloud. In particular, by looking

for correlations in the noise we were able

to detect atom-pair correlations, including

both spatial correlation and momentum

correlations. In the future, this new tech- nique could be used to detect the pairing

of atoms in a Fermi superfluid.

Figure 5. P-wave molecules, seen after

dissociation.

Another exciting direction for future work

is exploring the possibility of creating new

types of Fermi superfluidity. To this end, we have explored the possibility of creating

a new type of atom pairs using a p-wave

Feshbach resonance in the ultracold Fermi

gas. We successfully created and detected p-wave molecules, as well as p-wzve

quasi-bound states. We measured both the energy of these pairs and their lifetime as a function of magnetic field. Unfortunately,

the measured lifetime of the molecules is

relatively short and appears to be limited by molecule-atom collisions.

Contact: Dr. Deborah Jin (303) 492-0256

jin@jilau1 .colorado.edu

Cold Molecules

We have performed the first experimental

and theoretical investigations of ground

state polar molecules confined within a potential surface defined by combined

electric and magnetic fields. This type

of trap is novel as the molecule has both

electric dipole and magnetic dipole moments, causing complex dynamics within

the spatially inhomogeneous electric and

magnetic fields. Unlike previous work

where ground state polar molecules were

trapped inside an electric trap, the new

trap configuration gives the freedom to
48 NIST Physics Laboratory

apply an external electric field to control dipole-dipole interactions while keeping

the molecules trapped in an inhomogeneous magnetic field.

This capability will be important for precision measurements and for study

of dipolar gas physics and cold dipolar

collisions and reactions. We have already

used this trap to determine the collision

cross section between cold molecules and

hot background gas. In addition, we made

clear observations of single particle dynamics inside the trap that are in excellent agreement with theory.

Figure 6. Absorption images of a gas of ultracold heteronuclear molecules expanding

after release from the trap. Elapsed time on

top frame is 1 ms, middle 3 ms, and bottom

6 ms.

We see a possibility of producing ultracold polar molecules from ultracold gases, using

Feshbach resonances and optical transitions. For this experiment we have built an apparatus that is capable of producing

ultracold-atom gas mixtures and accessing

magnetic-field Feshbach resonances.

Rapid progress has been made in this ex- periment. Using an interspecies Feshbach

resonance, we have created and detected heteronuclear Feshbach molecules, measured their binding energy as a function

of magnetic field, and studied various molecule-atom collisions that limit the molecule lifetime. These results are very promising in that we have been able to realize relatively long lifetimes for ultracold, trapped molecules.

With these molecules we have begun optical spectroscopic measurements, exploring transitions to electronically excited molecule states. We have seen a dramatic

enhancement in these excitation rates when starting with Feshbach molecules,

compared to photoassociation of ultracold atoms. Future work will employ multiple

optical frequencies, referenced to an optical frequency comb, to drive these weakly

bound molecules to more deeply bound

states.

Contact: Dr. Jun Ye

[303)735-3171

yeOjila.colorado.edu

fhe third strategic element is to

advance ultrafast science.

ULTRAFAST SCIENCE

INTENDED GUTCGME AND

BACKGROUND

Ultrafast science has traditionally exploited

ultrashort optical pulses with durations as short as a few femtoseconds. These pulses

provide precise time resolution and/or high

peak powers. Because they are produced

by mode-locked lasers, their frequency

comb spectra can be controlled with the techniques described in the first strategic element. In ultrafast science, the control of

the comb spectrum corresponds to control of the electric field of the pulses in the time domain. Control of the electric field of the pulses enables the observation of

unique physical phenomena and the ability

to coherently synthesize new pulse shapes.

Traditional ultrafast techniques are used

in the Division to study the interactions of excitons in semiconductors, collision dynamics in atomic vapors, and the motion of biomolecules, providing technologically important information for both

optoelectronics and biotechnology. We use phase stabilization to improve measure- ment techniques and develop radical new

ultrafast technologies such as "gainless"

amplification of femtosecond pulses in a build-up cavity.

ACCOMPLISHMENTS

Femtosecond Enhancement

Cavities

The use of femtosecond enhancement

cavities continues to push the frontiers on

wide-bandwidth molecular detections and

VUV frequency comb generation. Optical

frequency comb-based cavity-ringdown

spectroscopy has recently enabled high sensitivity absorption detection of molecules

over a broad spectral range.

We have demonstrated an improved

system based on a mode-locked erbiumdoped fiber laser source centered at

1.5 pm, resulting in a spectrometer that is inexpensive, simple, and robust. It provides

a very large spectral bandwidth (1.45 pm

to 1.65 pm) for investigation of a wide

variety of molecular absorption features. Strong molecular absorption at 1.5 pm al- lows for detection at sensitivities approaching the level of 1 nL/L. We have performed measurements of the rovibrational spectra

for CO, NH,, Hp, and C^H^ with an

absorption sensitivity of 10'* cm 'Hz ''^'

per detection channel. Spectral resolution has been dramatically improved to less than 1 00 MHz, easily useful for isotope

identification.
Quantum Physics Division 49

Femtosecond enhancement cavities can also be used to reach high intensities, which are usually achieved by using

low repetition rate, expensive optical

amplifiers. High-harmonic generation

at 136 MHz repetition rate has been

produced with a cavity enhanced, Yb-fiber frequency-comb laser. The intracaviry field peak intensity reaches above 3 x 10"^ W/

cm', corresponding to a record high

3.5 kW average power. We have demonstrated laser-induced plasmas and highharmonic generation in Xe, Kr, and Ar. High-harmonic signals after an Al filter have been observed, thus it is clear that we

are now reaching shorter wavelengths in comb generations than ever before.

Contact: Dr. Jun Ye

(303)735-3171

yeOjila.colorado.edu

Optical Two-Dimensional Fourier

Transform Spectroscopy

An optical two-dimensional Fourier transfijrm spectrometer has been developed and

is being used to study many-body effects

in semiconductors. Multidimensional Fourier-transform spectroscopy was originally

developed in nuclear magnetic resonance

using radio frequencies. Recently there has been significant work to bring these tech- niques to infrared and optical frequencies.

Achieving the necessary phase control and

stability is a challenge. We have achieved it by using actively stabilized delay lines.

Many-body effects in semiconductors were extensively studied using traditional

ultrafast spectroscopic techniques. While

the experimental results proved the nonlinear signals are dominated by many-body

effects, they were unable to disentangle the various terms. Optical two-dimensional

Fourier transform spectroscopy excels at separating the various contributions to the

signals. The separation is in part due to the

spreading of the signals in two dimensions and also because full phase information can be obtained. The experimentally

obtained spectra have been compared to calculations and show good agreement, but only when terms beyond the standard Hartree-Fock approximation are included.

a)

Figure 7. Two-dimensional Fourier Transform spectra of exciton resonances in a GaAs Ineterostructure. (a) is experimental

data, (b) is theory within a Hartree-Fock

approximation, and (c] is a full theory

including terms beyond Hartree-Fock.

A second-generation spectrometer is under

development. It will allow all excitation pulses to be phase locked, not just two, as

is the case for the current spectrometer.

The new spectrometer will be used for continuing studies on semiconductors and for studies of atomic vapors and proteins.

Contact: Dr. Steven T. Cundiff [303] 492-7858

cundiffs@jila.colorado.edu

Grism-Based, ScalableRepetition-Rate Ti:Sapphire

Amplifier

Working with academia and industry, Division scientists have developed efficient

reflection grisms (gratings in contact with

prisms) for pulse compression in femto- second Tirsapphire laser amplifiers. These components simplify and miniaturize the

optics required for commonly used femtosec- ond amplifier systems. A simple and efficient grism-based femtosecond amplifier system

that produces 36 fs, 300 pj pulses at 5 kHz

to 1 5 kHz repetition rates was demonstrated

using the down-chirped pulse amplification

technique.

Contact: Dr. Ralphi Jimenez

(303) 492-8439

rjimenezOjilaul .colorado.edu
50 NIST Physics Laboratory

[he fourth strategic element

is to apply cutting edge

measurement science to biological

systems.

BIOPHYSICS

INTENDED OUTCOME AND

BACKGROUND

The Quantum Physics Division investigates important biological systems at the single molecule level, thus leveraging our measurement expertise and experi- ence with atomic and quantum systems.

Accordingly, we are evolving a part of our

research program in this direction to help

NIST contribute to the scientific revolution taking place in the biosciences.

The Division's strengths are the foundation

for our efforts to contribute to groundbreaking research on biological systems.

These strengths include our ability to build

institutional bridges to renowned university departments, a superlative infrastructure, experience in manipulating and

measuring atomic and quantum mechanical systems, and a reputation that allows

us to attract and hire the best and brightest of today's young scientists. Our new

biophysics program is being implemented

in close collaboration with the Department

of Molecular, Cellular, and Developmental

Biology and the Biochemistry Division of

the Chemistry Department at the University of Colorado. We expect that bringing

additional departments into JILA will enhance the very productive interdisciplin- ary character of the institute. Most importantly, because of our existing expertise,

NIST's bioscience program should rapidly

acquire the high stature achieved by our

other programs.

ACCOMPLISHMENTS

Subnanometer Optical

Tweezers Measurements of

DNA Molecular Motor

Single molecule experiments are revo- lutionizing biophysics. Optical traps,

also known as optical tweezers, can hold

micrometer-sized beads in three dimensions, apply calibrated piconewton-scale

forces, and measure displacement with

atomic precision.

Atomic-scale sensitivity is most useful for biology if it can be maintained over peri- ods sufficient to average Brownian motion,

and thus reveal the underlying protein motion. The most widely used single molecule

experiments are anchored to surfaces, but

drift of this surface prevents them from

being atomically precise. To address this shortcoming, the Division has developed

an actively stabilized, optical-trapping

microscope based upon improved laser

stability and the introduction of a fiducial mark firmly attached to a cover slip.

To demonstrate the capabilities of this microscope, measurements were made on a DNA helicase. DNA helicases are molecular motors that unwind DNA, which

is critical to the replication and repair of

the genome. As they hydrolyze adenosinetriphosphate (ATP), they unwind the DNA duplex.

Pioneering work on a super-family one

(SFl) helicase provided the first direct evi- dence for the step size of a helicase. These

single-turnover biochemical unwinding

experiments showed a rate limiting step every 4 to 5 base pairs (bp). This large "kinetic" step size has been seen in other SFl

helicases for unwinding double stranded DNA (dsDNA). In contrast, recent crystal- lographic studies of SFl helicases bound

to DNA, in different nucleotide states, suggested one base pair motion per ATP.

Fluorescent ATPase assays also show 1 ATP/bp. Thus, the mechanism and step

size of SFl helicases (if a single step size is even correct) remains unresolved.

Figure 8. An optical trap stretches a DNA

molecule. One detector laser measures

the trapped bead position, while the other one measures the sample drift. This drift

is then actively suppressed by moving a piezoelectric stage in three dimensions.

To address this ongoing uncertainty, we

directly measured the physical step size of a SFl helicase (RecBCD) along DNA

using a single-molecule, optical-trapping

assay with atomic-scale resolution. With

this enhanced resolution, we note three

significant results. First, RecBCD takes

distinct steps of variable size (2 bp to 7 bp,

occasionally larger). Second, the average observed step size is 4. 1 bp, which agrees with the previously determined kinetic step

size (3.9 bp). Third, we see an unexpected

backward motion of a few base pairs at moderate force and low ATP levels, consistent with a kinetic competition between

reannealing of the unwound DNA and

forward helicase activity.

Contact: Dr. Thomas T. Perkins

[303] 492-81 86

tperkins@jila.colorado.edu

Femtosecond Spectroscopy of

Heme-proteins

Heme proteins fulfill diverse roles, important in both human health and in biotechnology. In the former, they serve as

carriers and storage molecules for oxygen and other small molecules in tissues, as

electron transfer mediators in mitochon-
Quantum Physics Division 51

drial respiration, and as drug metabolizers

in the liver. In technological applications,

heme proteins are being employed in toxic waste remediation and in hybrid bio-nanoelectronics systems.

Research on the function of heme proteins has largely focused on structure. However,

paralleling the growth in structural data,

a large body of evidence has accumulated

showing that proteins are flexible molecules, continuously undergoing structural fluctuations on timescales ranging

from femtoseconds to seconds or longer. Since protein motions are critical to their

kinetics (e.g. the access of molecules to

their interiors) and thermodynamics (e.g. entropy), there is a compelling need to quantify the relation between structure, dynamics, and function.

We have performed photon echo spectros- copy on heme proteins, and have used a combination of experiments and theory to demonstrate that, with an understanding

of the symmetry properties of the heme,

this popular measurement technique can

be used to provide information on protein

motions. The development of this method

sets the stage for detailed studies of physiologically and industrially relevant heme

proteins.

Contact: Dr. Ralph Jimenez

[303] 492-8439

rjimenez@jilau1 .colorado.edu

Real Time Folding Kinetics of

Single RNA Molecules

The ability to image fluorescence from

single biomolecules represents one of the major scientific achievements of the last decade. In combination with time-correlat- ed single photon counting, these methods now offer an unprecedented window into

kinetics and dynamics of single biomolecules. They completely avoid the "blurring"

that unavoidably occurs in any collection of molecules due to ensemble averaging.

The biomolecules are labeled with donor

and acceptor dyes, where the efficiency

of fluorescence resonance energy transfer (FRET) from initially excited donor to ac- ceptor is a strong function of the biomolecular conformation. For donor/acceptor

dye pairs bound to a folding biopolymer,

the FRET efficiency

^ (i.e., / 7(7 ,+/ )) red red green and polarization anisotropy information

are monitored in real time and used to provide conformational information from

the well known distance and alignment

dependence for dipole-dipole energy transfer.

Figure 9. The P4-PB domain of the Tetrahymena thermophyla group 1 Intron. The "tetraioop/tetraloop receptor" and

"A-rich bulge" are ubiquitously present in ribozymal RNA.

Work in the Division has focused on real time folding dynamics of small RNA

sequences, using single molecule FRET

methods to explore tertiary "loop-loop"

interactions responsible for making larger

ribozymal RNA fold into biochemically

active conformation. The specific system

of interest is the P4-P6 domain of the Tetrahymena thermophyla group 1 Intron,

in particular the presence of two classic

tertiary binding motifs (the "tetraloop/

tetraloop receptor" and "A-rich bulge")

ubiquitously present in ribozymal RNA.

This system is an interesting target from a biophysical perspective because we know

the exact RNA sequence, and therefore can

successfully design relatively simple constructs that recapitulate a specific tertiary

motif in isolation.

Recently, we have focused on developing new experimental "burst" capabilities for studying single RNA constructs freely diffusing in solution, which permit a rigor- ous control for ruling out possible surface tethering effects on the kinetics. Data

reveal "bursts" of fluorescence as single

RNA molecules diffuse into and out of the focused laser excitation volume (=0.1 fL). Analysis of the "red" vs. "green" photon arrival statistics permits us to infer the FRET

value and therefore the folded vs. unfolded

conformation of an individual RNA as a function of external stimulus (e.g., [Mg*']).

Contact: Dr. David Nesbitt

[303] 492-8857

djn@jila.colorado.edu
I Research Area*

n t QpHeal Physlci- (

<) lechjTotogy let (Jeierminiog

rafed spectra) regions. minq Radiation : provicJi

n Physics: coixJucts n

• The Official U.S. Time

• Physical Reference Oatei Physics Lab News

It WST

:i NMR in tiny samples ol fluids fiowng

ji mtcrDchjp. The prototype chip

GOAL

To coordinate and facilitate

the electronic dissemination of

information via the Internet

WWW DISSEMINATION

OF INFORMATION

INTENDED OUTCOME AND

BACKGROUND

The Office of Electronic Commerce in

Scientific and Engineering Data (ECSED) is

responsible for the Physics Laboratory (PL)

World Wide Web pages at

http://physics.nist.gov.

We produce material for Web publication, encourage and support the production of

material by others, and ensure the high

quality of disseminated information. We

are also engaged with PL Divisions and the Measurement Services Division ofTechnol- ogy Services in developing physical reference databases for Web dissemination. We design

and develop effective Web database interfaces

to facilitate access to the data, providing data

in multiple formats suitable for customer

needs.

Since June 1994, we have provided a wide

array of information ranging from physical

reference data, technical activities, research and calibration facilities, technical contacts, publication lists, general interest, and news

Office of Electronic

Commerce in Scientific

and Enaineerina Data

The strategy for meeting this goal is to publish Physics Laboratory information on the World Wide Web, to develop web-accessible databases ofphysical reference

data, and to evolve protocols to ensure interoperability in the exchange of scientific and engineering data.

ACCOMPLISHMENTS

Units Markup Language

We have continued to develop an XML

(extensible Markup Language) schema

for encoding scientific measurement units. This includes initiating an OASIS (Organization for the Advancement of Structured Information Standards) UnitsML Technical Committee to finalize the development

of the UnitsML schema. Adoption as a standard will allow for the unambiguous exchange of numerical data over the

Internet.

To complement the UnitsML schema, we

are in the process of developing a database (UnitsDB) containing detailed information on both SI and non-SI scientific units. We anticipate UnitsDB will be used by our

customers to download industry-specific

dictionaries of scientific units, using a Web

Services interface.

We are also planning to develop a general ontology to describe the relationship

between measurement quantities independent of any specific system of units. These

activities are supported in part by the NIST Systems Integration for Manufacturing Applications (SIMA) program.

items. For the most recent six months, there was an average of nearly 2 million requests

for web pages per month fi^om the Gaithers- burg server, over half coming from about 30

online databases containing physical refer- ence data. A complete list of our databases is

available at http://physics.nist.gov/data.

Recent work includes the development of new (1-4) and updated (5—11) Web databases:

1 . Atomic Energy Levels and Wavelengths Bibliographic Database

2. NLTE4 Plasma Population Kinetics Database

3. SAHA Plasma Population Kinetics Database

4. FLYCHK Collisional-Radiative Code

5. Fundamental Physical Constants

B. Searchable Bibliography on the

Constants

7. Atomic Spectra Database

8. Energy Levels of Hydrogen and

Deuterium

9. Atomic Transition Probabilities Bibliographic Database

1 . Atomic Spectral Line Broadening

Bibliographic Database

1 1 . X-ray Transition Energies
Office of Electronic Commerce in Scientific and Engineering Data 53

Support for Publication of the

DLMF

Abramowitz and Stegun's Handbook of

Mathematical Functions (with Formulas,

Graphs, and Maihematical Tables) was

first published by the National Bureau of

Standards in 1964. It remains a technical

bestseller and is among the most widely

cited of all math reference compendia. But

the Handbook is increasingly out of date,

especially its numerical tables which ac- count for over half its length. It also lacks many recent developments in the theory

and computation of functions that find essential use in physics and other sciences.

A project is underway at NIST to develop

a replacement that will become a major

resource of math reference data for special functions and their applications. The new

Digital Library ofMathematical Functions {DLMF ) will appear in a hardcover edition and as a free electronic publication on the Web, at http://dlmfnist.gov/. The

completed hardcover edition will be over 1000 pages in length and is scheduled to be printed in 2008.

We provided support to the development

of the DLMF. This assignment entailed

electronic editing of existing chapters with

extensive handwritten corrections, and

adding new sections from handwritten

text. We began working on the DLMF in August 2003 (providing up to 40 % of one staff person per year) and ultimately

contributed to all 37 of its chapters.

Contact: Dr. Robert Dragoset

[301] 975-3718

robert.dragoset@nist.gov

NIST Atomic Spectra BiblioqRAphic DataBases

New Capabilities for On-Llne Databases

lomic Transition Probabilil

Bibliographic Databas^

The NIST Atomic Transition Probability

Bibliographic Database (http://physics.

nist.gov/fvalbib) has been available online since 1994, and was one of Physics

Laboratory's first physical reference databases available on the Web. This database

contains references to publications that include numerical data, comments, and

reviews on atomic transition probabilities

(oscillator strengths, line strengths, or

radiative lifetimes). The initial database contained approximately 2300 references. The current database now contains 7465

references, dating from 1914 through

2007.

, AtomijcTEnergy Leve.is|^^

tepectra^Bibliog'raphi^Q^^^^^

We recently collaborated with Physics

Laboratory's Atomic Spectroscopy Data

Center to release an on-line version of the NIST Atomic Energy Levels and Spectra

Bibliographic Database (http://physics.

nist.gov/elevbib). Its references pertain

to atomic structure and spectra that arise from interactions or excitations involving

electrons in the outer shells of free atoms and atomic ions, or from inner shell excitations corresponding to frequencies up to the soft x-ray range. This interactive data- base allows access to references on atomic

energy levels and wavelengths. Preference is given to experimental papers. The database

contains approximately 10880 references, dating from 1892 through 2007.

temic SpectrailLine wsgMjgmHj

iBibiioqra'phic Pata^Sa

The NIST Atomic Spectroscopy Data

Center also maintains an additional biblio- graphic database that contains references

to publications that include numerical

data, general information, comments, and

reviews on atomic line broadening and

shifts (http://physics.nist.gov/linebrbib).

The NIST Atomic Spectral Line Broadening Bibliographic Database, on-line since 1998, has been updated to contain 3666

references, dating from 1961 through

2007.

These bibliographic databases have a wide

customer base including major corporations, government laboratories, and universities. The users of these databases include

scientific researchers working in atomic

physics, laser physics, lighting, semiconductor fabrication, material processing,

biophysics, thermonuclear fusion, astrophysics, and chemistry.

Contact: Ms. Karen Olsen

[301] 975-3286

karen.olsen@nist.gov
Awards and Honors

NOBEL PRIZE IN PHYSICS

John ("Jan") L. Hall, Scientist

Emeritus in Quantum Physics

Division and a Fellow ofJILA, a

joint research institution of NIST

and the University of Colorado in

Boulder, Colorado. Dr. Hall shared

the 2005 Nobel Prize in Physics with

Theodor W. Hansch of the MaxPlanck-Institute for Quantum Optics

(Catching, Cemany) and LudwigMaximilians-Universitat (Munich,

Germany) and Roy J. Clauber of

Harvard University. Hall and Hansch

were cited, "for their contributions

to the development of laser-based

precision spectroscopy, including the

optical frequency comb technique."
Awards and Honors 55

Herbert P. Broida Prize

(American Physical Society)

In recognition ofan outstanding contribution

to thefield ofatomic and molecidar spectroscopy or chemicalphysics

1!^

James Bergqiiist, Time and

Frequency Division, 2007

Prize, "for seminal contributions to ultra-high-resolution laser spectroscopy and

the realization of accurate

optical frequency standards"

I.I. Rabi Award (IEEE Society for

Ultrasonics, Ferroelectricity,

and Frequency Control)

To recognize outstanding contributions

related to thefields ofatomic and molecidar frequency standards, and time transfer and

dissemination

James Bergquist, 2006 Award, "for seminal contributions to laser spectroscopy and

the realization of accurate optical frequen- cy standards"

Leo Hollberg, Time and

Frequency Div., 2007

Award, "for seminal

contributions to optical

frequency metrology with

the development of ultra

stable optical frequency standards and

related femtosecond clockwork"

De Boer Services Gold Pin

(International Commission on

Illumination (CIE))

Yoshi Ohno, Optical

Technology Div., for exceptional administrative and scientific contributions to the physical measurement of light and

radiation

William F. Meggers Award

(Optical Society of America)

For outstanding work in spectroscopy

JunYe, Quantum Physics

Division, 2006 Award,

"for development of

innovative spectroscopic measurement techniques based on femtosecond

optical frequency combs"

Carl Zeiss Research Award

Jun Ye, 2007 Award, for his outstanding

applications of femtosecond frequency

combs

I.I. Rabi Prize in Atomic,

Molecular and Optical Physics

(American Physical Society)

To recognize and encourage outstanding

research in Atomic, Molecular and Optical

Physics by investigators who have held a

Ph. D. for 10 years or less

Jun Ye, 2007 Prize, for advances in precision measurement, including techniques for

stabilizing and measuring optical frequencies, controlling the phase of femtosecond

laser pulses, and measuring molecular

transitions

Deborah Jin, Quantum

Physics Division, 2005

Prize, for her pioneering

work in the production of

degenerate Fermi gases and exploitation of their novel physical properties

George C. Pimentel Prize for

Advances in Matrix Isolation

Spectroscopy

Marilyn Jacox, Scientist Emeritus, Optical

Technology Division,

2005 Prize, for her many

major contributions to matrix isolation spectros- copy, including, most recently, investigations of highly unstable negative ions and

negative ion clusters

Doctor of Science (Honoris

Causa), University of Waterloo

Marilyn Jacox, 2006 Award, "for her long and distinguished career in physical

chemistry"

European Young Scientist

Award

Scott Diddams and Svenja Knappe, Time

and Frequency Division, 2007 Award from

the European Frequency and Time Forum,

for Diddams' work on femtosecond laser frequency combs, and for Knappe's work

on chip-scale atomic devices

The Texas A & M Trotter Prize

and Endowed Lecture Series

William Phillips, Atomic

Physics Division, 2006

Prize, for pioneering

contributions to the understanding of the connections between

science and religion and their role in

establishing a consistent worldview
56 NIST Physics Laboratory

Member of the National

Academy of Sciences

Deborah Jin, Quantum

Physics Division, for her work in the rapidly

advancing field of

experimental ultracold fermions

Fellowship of the American

Association for the

Advancement of Science

Deborah Jin, Quantum Physics Division,

for advances in the study of quantum gases and the properties of a Fermi degenerate gas

Alfons Weber, Scientist Emeritus, Physics

Laboratory, for playing an

important role in the development of molecular

physics as a researcher and

as a manager of Federal programs at NIST

and NSF

Fellowship of the American

Academy of Arts and Sciences

Eric Cornell, Quantum

Physics Division, for preeminent contributions

to the science of Bose

Einstein condensation and

to society at large

Deborah Jin, Quantum Physics Division,

for preeminent contributions to the science of ultracold, degenerate gases

Fellowship of the American

Physical Society

Garnett Bryant, Atomic

Physics Division, for seminal contributions to nanooptics and to the theory of semiconductor

quantum dots and other complex quantum nanostructures

Steven CundifF, Quantum

Physics Division, for pioneering work in carrier- envelope phase

stabilization of modelocked lasers and its applications to optical frequency metrology

and ultrafast technology

Kristian Helmerson,

Atomic Physics Division,

for pioneering work in cooling, trapping, and

coherent manipulation of

cold atoms and for the development of seminal techniques for the manipulation and control of objects with

optical tweezers

Dietrich Leibfried, Time

and Frequency Division,

for seminal contributions

to the field of quantum

information processing

using trapped ions, includ- ing the demonstration of high fidelity logic

gates and the implementation and

application of entangled states

William Ott, Deputy

Director, Physics Laboratory, for sustained

leadership of the research and service programs of

the Physics Laboratory of

the National Institute of Standards and

Technology

Eric Shirley, Optical

Technology Division, for important contributions

to the computation of the

optical properties of solids from the infrared to the

x-ray spectral regions

Eite Tiesinga, Atomic

Physics Division, for pioneering work on the measurement and control of cold atomic collisions by scattering resonances

Fellowship of the Optical Society

of America

Steven Cundiff, Quantum Physics Division, for contributions to ultrafast laser spectroscopy of semiconductors and to carrier-envelope phase stabilization of

mode-locked lasers

Jun Ye, Quantum Physics

Division, for the application of frequency combs

and ultrafast and ultrastable lasers to precision measurements and

funda ital
Awards and Honors 57

Fellowship of the Illuminating

Engineering Society of North

America

Yoshi Ohno, Optical

^^^V^^^l Technology Division, for ^B^ -i^BH contributions to the Wf^\^^K^' rnetrology of light

through development of ^ measurement methods

and metrics and education of the lighting

metrology community

Fellowship of the Royal Society

of Chemistry

David Nesbitt, Quantum

Physics Division, for promoting the advance- ment of a wider application of chemical science

Fellowship of the Health Physics

Soceity

Chris Soares, Ionizing

Radiation Division, in recognition of outstanding

contributions to the profession of Health

Physics

Senior Member of the IEEE

John Curry, Atomic Physics Division, for progress

in developing energyefficient lighting

International LORAN

Association, Best Paper Award

Michael Lombardi, Time

and Frequency Division,

2006 Award, for the paper "The potential role of

enhanced Loran-C in the

national time and

frequency infrastructure"

IEEE International Solid-State

Circuits Conference Jack Paper

Award

John Kitching, Time and

Frequency Division, with

Clark T.C. Nguyen

(DARPA, Univ. Michigan), 2005 Award, for the paper "Towards chip-scale

atomic clocks"

National Conference of

Standards Laboratories

International, Best Paper

Award

John Kitching, Time and Frequency Division, 2005 Award, for "Chip-scale atomic

clocks at NIST"

Young Scholars Competition

Jun Ye, Quantum Physics Division, 2005

Technological Innovation Prize, for his paper "Optical phase control from 10"'^

seconds to 1 second: precision measure- ment meets ultrafast science"

American Physical Society,

Outstanding Doctoral Thesis

Research in Atomic, Molecular

and Optical Physics

Cindy Regal, University

fW-- of Colorado and guest

; researcher in Quantum

~ ^I^M Physics Division, 2007

\ Award for, "Experimental

realization of BCS-BEC

crossover physics with a Fermi gas of atoms"

Ana Maria Rey, University of Maryland and guest

researcher in Electron and

Optical Physics Division,

2005 Award for, "Ultra- cold bosonic atoms in

optical lattices," conducted at NIST

American Physical Society, Best

Student Paper {in Experiment]

Chris Langer, U. of

Colorado graduate student

in Time and Frequency

Div., 2006 Award, for "Robust quantum

memory using magneticfield-independent atomic qubits"

Optical Society of America,

New Focus / Bookham Student

Award

Virginia Lorenz, U. of

Colorado graduate

student in Quantum

Physics Division, 2006

Award, for her presentation "Three-pulse photon

echo peak shift measurements in dense potassium vapor"
58 NIST Physics Laboratory

Arthur S. Flemming Awards

Established in 1948, the Flemming Awards

honor outstanding Federal employees with no more than 15 years ofgovernment service. About ten winners are selected each yearfrom

all areas ofthe Federal service.

David Jacobson, Ionizing

Radiation Division, 2006

Applied Science, for applying neutron metrol- ogy techniques to address

technical barriers to the development of robust and efficient hydrogen fuel cells

Steven JefFerts, Time and

Frequency Division, 2004

Applied Science, for outstanding technical and

managerial leadership of

NIST-Fl, the world's most

accurate atomic clock

Keith Lykke, Optical

Technology Division,

2004 Applied Science, for the development of novel

laser technology for the accurate calibration and

characterization of optical instruments used in ground and satellite-based remote

sensing, missile defense and targeting, and

standards research, development, and

dissemination

Yoshi Ohno, Optical

Technology Division,

2005 Applied Science, for

his innovative research and international leadership in the optical sciences of photometry and colorimetry

James "Trey" Porto,

Atomic Physics Division,

2006 Basic Science, for an

experimental program and

research team to attack the problem of quantum

processing with neutral atoms, establishing

NIST's program in neutral atom quantum

information as one of the top in the world

Carl Williams, Chief

Atomic Physics Division,

2005 Basic Science, for

definitive theories of the physics ot ultracold atoms and molecules and their application to precision measurement,

atomic clocks, and the new fields of

Bose-Einstein and fermionic condensation

and quantum computing

Jun Ye, Quantum Physics

Division, 2004 Basic

Science, for his contributions to the fields of

precision measurement,

quantum optics, ultrasensitive detection, and cold molecules

Bonfils-Stanton Foundation

Recognizes outstanding Coloradansfor

significant and unique cotttributions in the

arts and humanities, community service, and

science and medicine

Deborah Jin, Quantum

Physics Division, 2006

Award for Science and

Medicine, for her work in the field of ultracold Fermionic gases

Service to America Medals

Presented by the Partnership for Public

Service to celebrate excellence in federal civil

service

Konrad Lehnert,

Quantum Physics

Division, was a 2007

finalist for the Call to Service Medal, for pushing

the frontiers of measure- ment science up against the ultimate limits imposed by the famous uncertainty

principle of quantum mechanics

William Phillips, Atomic

Physics Division, was awarded the 2006 Career Achievement Medal for

service as an ambassador

for science and the

Federal workforce

Presidential Rank Awards

Recognizes Senior Executivesfor exceptional

long-term accomplishments

Robert Celotta, Electron and Optical Physics

Division & CNST, 2006

Award for Distinguished

Senior Professional, for pioneering research in nanotechnology

Charles Clark, Chief

Electron and Optical

Physics Division, 2007

Award for Distinguished

Executive, for establishing

SURF III as the Nation's preeminent facility for ultraviolet radiation measurements and for maintaining a vigorous program of

personal scientific research
Awards and Honors 59

James Faller, Quantum

Physics Division, 2006

Award for Meritorious

Senior Professional, for a

career dedicated to precision measurement

science with an emphasis on experimental

gravitational physics and tests of funda- mental physical laws

Katharine Gebbie,

Director, Physics

Laboratory, 2006 Award

for Distinguished

Executive, for sustained,

extraordinary leadership

and dedication in creating and managing

the NIST Physics Laboratory to an

unprecedented level of excellence

Paul Julienne, Atomic

Physics Division, 2007

Award for Meritorious

Senior Professional, for being one of the world's preeminent theorists in the

fields of photoassociation and ultracold

collisions

William Phillips, Atomic

Physics Division, 2005

Award for Distinguished

Senior Professional, for his leadership in the development of laser cooling and

trapping of atoms and its application to atomic clocks and neutral atom quantum

computing

Presidential Early Career Award Accenture Government

for Scientists and Engineers Women's Leadership Award

Established in 1 996, the highest honor

bestowed by the U.S. government on scientists and engineers beginning their independent

careers

Joshua Bienfang,

Electron and Optical

Physics Division, 2006

Award, for outstanding

research in quantum

communications and

experimental quantum cryptography

James "Trey" Porto,

Atomic Physics Division,

2005 Award for worldclass research on neutral- atom quantum computing

and novel quantum

properties of atoms in one-dimensional

systems

Washington Academy of

Sciences Physical Science

Award

Paul Julienne, Atomic Physics Division,

2005 Award, for pioneering studies of the theory of ultracold atomic collisions and

its numerous applications that continue to impact forefront research, from Bose-Einstein condensation to atomic clocks

Albert Parr, Optical

'» Technology Division,

2006 Award, for leader- ship in developing

state-of-the-art optical measurement facilities in support of national programs crucial to the U.S. economy and defense preparedness

Katharine Gebbie, Director, Physics

Laboratory, 2006 Award in the Govern- ment Visionary category. "In her 15 years of leadership at NIST's Physics Lab, Dr. Gebbie has repeatedly proven her dedication to the spirit of scientific discovery

and teamwork. Under her direction,

scientists from NIST have received three Nobel Prizes, and her leadership has led

to improvements in the quality of clinical mammography, port entry radiographic

devices, and the irradiation of potentially

contaminated mail."

R&D 1 00 Award

Joshua Bienfang, Electron and Optical

Physics Division, 2007 Award, for NIST's

high-speed fiber-based quantum key distri- bution system, able to transmit at gigabits per second and produce megabits per second of secure key, twice as fast as any

other existing quantum key system

Scientific American 50

David Wineland, Time

and Frequency Division,

in 2006, for his research on quantum computing

and for fabricating chips

capable of storing just a few ions, paving the way for more

elaborate chips that can manipulate ions in more serious numbers
60 NIST Physics Laboratory

Gold Medal (DoC)

JJje highest honor conferred by the Department ofCommerce, for distinguished

performance characterized by extraordinary,

notable, or prestigious contributions that

reflectfavorably on the Department

Lisa Karam, Chief,

Ionizing Radiation

Division, 2006 Gold

Medal, "for her leadership

in developing radiation standards and measure- ment methods needed in the national

effort to ensure protection from terrorist

attack"

Jabez McClelland,

Electron and Optical

Physics Division &

CNST, 2006 Gold Medal,

"for pioneering

experiments on the

fabrication and replication of permanent

nanostructures based on an atom optical control of molecular beam epitaxy"

Thomas Parker and Judah Levine, Time

and Frequency Division, 2007, for their

"leadership of the NIST time scale, the source of all NIST time and frequency measurements

used billions of times each day"

Joseph Stroscio, Electron and Optical Physics Division & CNST, 2005

Gold Medal, "for the development of new

instruments and methods

to measure nanostructure properties and

for seminal research in nanoscale science and technology"

Silver Medal (DoC)

For exceptionalperformance characterized by

noteworthy or superlative contributions that have a direct and lasting impact within the Department

Raju Datla, Optical

Technology Division,

2005 Silver Medal, "for directing the development

of innovative infrared

optical measurement

technology and standards to support

critical national needs in missile defense and climate-change research"

Mitchell Furst, Electron and Optical Physics

l~ I Division, 2006 Silver W ^— Medal, "for outstanding

improvements in performance oi the NIST

SURF III Synchrotron Ultraviolet Radiation Facility"

Leonard Hanssen,

Optical Technology

Division, 2007 Silver Medal, "for seminal

contributions to infrared measurement science and

technical standards in support of civilian and defense applications of remote

sensing"

Edwin Heilweil, Optical

Technology Division,

2007 Silver Medal, "for advancing the state-of-theart in terahertz technology

and data for applications

in defense, homeland security, and

manufacturing"

Kristian Helmerson,

Atomic Physics Division,

2007 Silver Medal, "for pioneering the field of

coherent atom optics and

persistent atom currents"

Jeeseong Hwang, Optical

Technology Division,

2007 Silver Medal, "for the development of

innovative nanotechnology

tools for the highly

selective and sensitive optical detection of

bacterial pathogens"

John Kitching, Leo HoUberg, Hugh

Robinson, and Peter Schwindt, Time

and Frequency Division, and John

Moreland and Li-Anne Liew, EEEL

Electromagnetics Division, 2005 Silver Medal, "for designing, constructing, and

operating the world's first ultra-miniature atomic clocks and magnetometers"

Mark Stiles, Electron and

Optical Physics Division

& CNST, 2005 Silver Medal, "for exceptional contributions to the theory of magnetic

phenomena in nanostructures and thereby

furthering U.S. competitiveness in the development of a wide array of magnetic

sensors and information storage devices"
Awards and Honors 61

Bronze Medal (NIST)

For work that has resulted in more effective and efficient management systems,

the demonstration ofunusual initiative or

creative ability, significant contributions on majorprograms, scientific accomplishment,

or superior performance

Julia Bachinski,

Quantum Physics

Division, 2006 Bronze

Medal, "for excellence in administrative support of

science at JILA"

Joshua Bienfang, Electron and Optical

Physics Divison, and Barry Hershman,

Alan Mink, Anastase Nakassis, and Xiao

Tang, Advanced Network Technologies

Division (ITL), 2005 Bronze Medal, "for outstanding performance in advancing

quantum cryptography towards commercial application"

Gamett Bryant, Atomic

Physics Division, 2007

Bronze Medal, "for exceptional contributions

to the theory of

nanomaterials,

semiconductor quantum wells, quantum

wires, quantum dots, and nanocrystallites"

Karen Olsen, Robert Dragoset, and

Gloria Wiersma, Office of Electronic Commerce in Scientific and Engineering

Data, 2005 Bronze Medal, "for pioneering

the dissemination of physical reference data on the WWW and for providing

outstanding customer service for more

than 10 years"

Alex Farrell, Electron and

;

' Optical Physics Division,

2005 Bronze Medal, "for outstanding service to customers of the NIST

SURF III Synchrotron

Ultraviolet Radiation Facility"

Gerald Fraser, Chief

Optical Technology

Division, 2007 Bronze

Medal, "for leadership in the development of

programs, facilities, and

partnerships in infrared and optical radiation measurement and standards"

^^^B^^^H David Jacobson,

Ionizing Radiation

Division, 2006 Bronze

Medal, "for his contribution in developing an advanced neutron imaging facility for fuel cell research"

Michael Lombardi and Andrew Novick,

Time and Frequency Division, 2007

Bronze Medal, "for development and

implementation of the SIM network

for precision international time

synchronization in North, Central, and

South America"

Cameron Miller, Optical

Technology Division,

2007 Bronze Medal, "for contributions to the

first-ever assessment of the U.S. measurement system's

ability to sustain innovation at a worldleading pace"

James "Trey" Porto,

Atomic Physics Division,

2006 Bronze Medal, "for the creation and leadership

of a program in quantum

information using neutral atoms as qubits"

Adriaan Carter and Eric Shirley, Optical

Technology Division, 2005 Bronze Medal,

"for developing innovative computational

and experimental methods to accurately

calibrate infrared sensors used in missile defense"
62 NIST Physics Laboratory

William P. Slichter Award

For outstanding achievements by NISTstaff

in building or strengthening ties between NISTand industry

Steven Grantham, Robert Vest, Charles

Tarrio, Thomas Lucatorto, and Shan- non Hill, Electron and Optical Physics

Division, 2007 Award, "for establishing

a firm measurement foundation for EUV

reflectometry, optics lifotime characterization, and pulsed radiometry for EUV

lithography"

John Burnett, Atomic

Physics Division, 2006

Award, "for his pioneering contributions to the development of immersion microlithography"

Colleagues' Choice Award

Recognizes nonsupervisory employees who,

in the eyes oftheir colleagues, have made

significant contributions that broadly

advance the NIST mission and strategic

goals or contribute to the overall health and

effectiveness ofNIST

Anita Sweigert, Physics

Laboratory, 2006 Award,

"for extraordinary

dedication to, and

administrative support for, the NIST Summer

Undergraduate Research Fellowship

(SURF) program"

Samuel Wesley Stratton Award

For outstanding scientific or engineering achievements in support ofNIST objectives

Jun Ye, Quantum Physics

Division, 2006 Award,

"for femtosecond comb

technology work which

merges time- and frequency-domain spectroscopic

techniques and is enabling new develop- ments in optical atomic clocks"

Allen v. Astin Measurement

Science Award

For outstanding achievement in the ad- vancement ofmeasurement science or in the

delivery ofmeasurement services

Howard Yoon and Charles Gibson,

Optical Technology Division, 2005 Award,

"for major advances in the realization and

dissemination of the NIST spectral irradi- ance scale, widely used in climate-change

research"

Edward Uhler Condon Award

For distinguished achievement in effective written exposition in science or technology

Michael Lombardi, Time

and Frequency Division,

2005 Award, "for publications aimed at informing not only

technical experts and

manufacturers about NIST time and

frequency services, but also the general

public"

Eugenne Casson Crittenden

Award

Recognizes superior achievement by per- manent employees who perform supporting

services that have a significant impact on

technicalprograms beyond their own offices

Eyvon Petty, Time and

Frequency Division, 2007

Award, "for outstanding

support of NIST Boulder

programs, including the Boulder SURF Program,

Boulder Labs seminars and colloquia, and

training Boulder staff'

Jacob Rabinow Applied

Research Award

For outstanding achievements in the practical

application ofthe results ofscientific engineering research

John Kitching, Time and

Frequency Division, 2007

Award, "for outstanding

leadership of NIST s world-leading chip-scale

atomic device program"

Sigma Xi (NIST Chapter)

Outstanding Postdoctoral

Presentation Award

Benjamin Brown and Patricia Lee, Atomic Physics Division, 2007 Award for

their paper, "A two-qubit quantum gate with neutral atoms in an optical lattice"
63

Sigma Xi (NIST Chapter) Young

Scientist Award for Excellence

in Scientific Research

Jason Grain, Electron and

Optical Physics Division

& CNST, 2006 Award,

for work leading to the discovery of "end states" in one dimensional atom

chains and elucidating electronic effects in

the length distributions of one dimensional

chains of atoms

ORGANIZATIONAL CHART

Department of Energy

Hydrogen Program R&D Award

Muhammad Arif,

Ionizing Radiation

Division, 2007 Award,

for his outstanding

achievement in fuel cell

research and development

NASA Group Achievement

Award

Joseph Reader, Gillian Nave, and Graig

Sansonetti (jointly with staff of the Space Telescope-European Coordinating

Facility), Atomic Physics Division, 2006

Award, in recognition of painstaking

efforts to provide maximum scientific value

to Hubble Space Telescope data using

precision laboratory spectral measurements and physical instrument modeling

techniques

Physics Laboratory

Katharine Gebbie, Director

William Ott, Deputy Director

B

Electron and Optical Physics Division

Charles Clark, Chief

Atomic Physics Division

Carl Williams, Chief

Optical Technology Division

Gerald Fraser, Chief

Ionizing Radiation Division

Lisa Karam, Deputy Chief

Time and Frequency Division

Thomas O'Brian, Chief

Quantum Physics Division

Steven Cundiff, Chief
64 NIST Physics Laboratory

PHYSICS LABORATORY RESOURCES

Key to Table Abbreviations

STRS Congressionally appropriated funds for NIST's Scientific and

Technical Research and Services

ATP Intramural research funds provided to support the goals of

the NIST Advanced Technology

Program

OA Funds provided by other

agencies in support of needed

research and measurement

Other Other sources of funding,

including calibration fees

PHYSICS LABORATORY RESOURCES 2003-2007

($ Millions]

|, 1003 -> r\r\ A 2004 2005 2006

i

2007

SIRS M 43.1 40.3 43.6 48.1 49.2

ATP 1 2.7 0.6 1.6 0.9 0.9

OA M 14.0 20.8 20.4 21.6 20.7

OTHER ^ 5.2 5.2 5.0 4.6 4.7

TOTAL 65.0 66.9 70.6 75.2 1 75.5

Federal Agencies Supporting

Physics Laboratory Research Representative Private Sector Collaborators

Department of Agriculture

Department of Commerce

Department of Defense

Department of Energy

Department of Health and Human

Services Department of Homeland Security

Department of Justice Department of State Environmental Protection Agency

National Aeronautics and Space

Administration

National Science Foundation

American Association of Physicists in Medicine

American Chemical Society

American Geophysical Union

American National Standards Institute American Physical Society

American Society for Testing and Materials Biophysical Society

Commission Internationale de I'Eclairage

Council for Optical Radiation Measurements

Council on Ionizing Radiation Measurements and Standards Health Physics Society

Illuminating Engineering Society of North

America

Institute of Electrical and Electronics Engineers

International Electrotechnical Commission

International Organization for Standardization

National Council on Radiation Protection and Measurements NCSL International Nuclear Energy Institute Optical Society of America

International SEMATECH

SPIE—The International Society for Optical Engineering
EDITORS: Jonathan E. Hardis and William R. Ott

Physics Laboratory, National Institute of Standards and Technology

U.S. Department of Commerce

Carlos M, Gutierrez, Secretary

National Institute of Standards and Technology! James M. Turner, Deputy Director

NISTSP 1075

May 2008

Disclaimer: Any mention of commercial products

is for information only; it does not imply NI5T

recommendation or endorsement, nor does it imply

that the products mentioned are necessarily the best available for the purpose.