AlllDb M772SS

Supportins U.S. Industry, Government, and the Scientific Community

by providins measurement services and researcli for electronic,

optical, and radiation technoiosy.

Nisr

National Institute of Standards and Technology

j : r^i?? Technology Administration

U.S. Department of Commerce
Physics Laboratory at a Glance 1

Director's Messase 2

Electron and Optical Physics Division 4

Atomic Physics Division 12

Optical Technolosy Division 20

lonizins Radiation Division 28

Time and Frequency Division 36

Quantum Physics Division 44

Office of Electronic Commerce in 52

Scientific and Ensineerins Data

Awards and Honors 54

Physics Laboratory Resources 63

Orsanizational Chart 64
PHYSICS LABORATORY AT A GLANCE

PL Vision

Preeminent performance in measure- ment science, technology, and services.

PL Mission

The mission of the NIST Physics

Laboratory is to support U.S. industry,

government, and the scientific community by providing measurement services

and research for electronic, optical, and

radiation technology. The Laboratory

provides the foundation for metrology

of optical and ionizing radiation, time

and frequency, and fiindamental quantum processes.

PL Goals

The Physics Laboratory develops goals

within its mission and focus areas. These

include health care quality assurance, nanoscale measurements and data, and

measurements and standards that support homeland security. In addition to

these over-arching focus areas, which are shared by other NIST Laboratories, PL

has substantial programmatic interest in

time and frequency, optical and photonic, and environmental and energy

metrology and 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 Technolosy Division: to provide the foundation for optical radiation

measurements for our Nation.

lonizins 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 measurement science, in partnership with the University of Colorado

atJILA.

Office of Electronic Commerce in

Scientific and Engineering Data: to coordinate and facilitate the electronic

dissemination of technical information

via the Internet.

PL Resources

192 full-time staff (140 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

$67 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-Accuracy Cryogenic Radiometry - 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) - Nanoscale Physics Laboratory - Neutron Imaging Facility - Neutron Interferometer and Optics

Facility (NIOF) - 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,

andWWVB

- Automated Computer Time

Service (ACTS) - Internet Time Service (ITS)

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/
e hope this report conveys the excitement and the relevance

of the prosrams within the NIST Physics Laboratory. First and

foremost, we support U.S. industry by providins measurement

sen/ices and research for optical, electronic, and radiation

technologies. Our great strength—and what distinguishes us from an academic or industrial laborator/—is that we are

vertically integrated. Our world-class measurement services

are backed by state-of-the-art engineering efforts to develop

new measurement standards, which are in turn supported by

frontier, mission-oriented research that anticipates the Nation's

future measurement needs.

Thus the Laboratory addresses the fundamental triad of standards, measureFor example, our Time and Frequency

Division is delivering seven different

kinds of time and frequency services

while also developing optical frequency

atomic clocks, chip-scale atomic clocks,

and a futuristic atomic clock for space

flight. While our Internet Time Service

provides official U.S. time in over a

billion daily transactions, we are also

pursuing research on trapped ions for

the next generation of frequency standards—and quantum-logic devices.

Similarly, our Ionizing Radiation

ments, and data in a climate of vigorous

and competitive research. We believe

that the quality of our service stems in

large measure from the breadth, vigor

and excellence of our research programs

and that our contributions gain credibility because they are based on the best

technical judgment available.

2
Division is developing highly sensitive

neutron detectors for homeland security

while also using ultracold neutrons to

investigate symmetries and parameters

of the nuclear weak interaction.

We maintain the U.S. national standards for the Systeme International (SI)

base units of time (the second), light

(the candela), and noncontact thermometry (the kelvin, especially above

1 200 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 is extensive. For optical radiation measurements, we rely heavily on

the Council for Optical Radiation

Measurements (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 infrared 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. When we can assist in an important area of measurement or research, we may form Cooperative Research and

Development Agreements with industry

groups or individual firms. Laboratory

scientists serve with distinction in stan- dards-development committees, and

readily give of their time to assist the

public.

We have been recognized for the quality

and excellence of our programs and

staff many times over the years, by the

American Physical Society, the Optical

Society of America, and other leading

scientific organizations. Members of our

staff have been elected to fellowship in

the National Academy of Science, the

American Association for the Advancement of Science, the American

Association of Physicists in Medicine,

and other esteemed bodies. Twice since

1 997, Laboratory scientists have won

the Nobel Prize in Physics. Beginning on page 54 of this report, we highlight some of the awards and honors

bestowed upon us recently.

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.

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.

Katharine Gebbie

Director, Physics Laboratory
GOAL

TO SUPPORT EMERGING

ELECTRONIC, OPTICAL,

AND NANOSCALE

TECHNOLOGIES

ELECTRON AND OPTICAL PHYSICS DIVISION

The strategy for meeting this goal is to improve measurement science and to

develop the measurements and standards needed by emerging science and

technology-intensive industries.

^l^e first stratesic focus is

to develop techniques for

fabricating nanostructures

and measuring tlieir

electronic and magnetic

properties.

Nanoscale Electronics

and Masnetics

INTENDED OUTCOME AND

BACKGROUND

The intended outcome of this work is

the continuous improvement of methods for fabricating and characterizing

nanometer-scale 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 pro- gram 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 begun at NIST in

the 1970s. SEMPA enables us to use

conventional scanning electron

microscopy (SEM) to image nanometerscale magnetic structure, through

spin-polarization 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

measurement 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 pro- gram has been particularly concerned

with the magnetic multilayer materials

that have been investigated 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 electronenergy resolution. Samples grown in situ

can be measured in an ultrahigh vacuum

environment with magnetic fields of up

to 10 T at temperatures down to 2.3 K.

Additionally, a program in Autonomous

Atom Assembly is underway that will

allow us to fabricate highly complex and

perfect nanostructures on demand.

4
ACCOMPLISHMENTS

Understanding Single Atom

Manipulation

A low-temperature STM can move

atoms about on clean, flat surfaces. However, our limited understanding of

the interactions involved restricts our

ability to make complex nanostructures.

We recently studied the atom dynamics

that occur during atom manipulation

important if we are to make real nanodevices on technological substrates. We found that the atoms at the end of an iridium STM tip create a potential

trap sufficient to capture a cobalt atom

adsorbed on a clean copper crystal and

to limit its lateral motion to less than

0.2 nm. We also discovered that the

vibrational level of the cobalt-copper

bond could be varied dramatically by

changing the electron current tunneling

into the cobalt atom.

By adjusting the proximity of the STM

tip to the cobalt atom, as well as the

current flowing through it, it is possible

to translate the cobalt atom across the

copper crystal surface in a controlled

and well-understood manner. It is even

possible to force the cobalt atom into

what is normally not a binding site on

I - ^ - - 4

-

Fisure 1 . Bindins site imase for a cobalt atom

on a copper (111) surface, showins three-fold

symmetr/.

the surface. As the conditions necessary

for forcing the atom into a nonbinding

site are approached, the atom begins to jump back and forth between the nonbinding site and a neighboring binding

site, giving rise to audio frequency noise

in the tunneling current. This noise can

be monitored in the laboratory and

correlates with the locations of the

nonbinding sites on the surface.

Using our newly acquired understanding

of the atom manipulation process, we

were able to: obtain a direct observation

of a characterizable random two-state

fluctuator, demonstrate the ability to modify single atom surface dynamics,

show how chemical binding sites can be

modified to change unstable ones to stable and vice versa, provide the first

explanation for the origin of excess tunneling noise, and present a new type of

STM image that reveals the surface

binding sites of the crystal. (See Fig. 1 .)

This work is an example of a new

class of measurements referred to as "Atom-Based Metrology," where a single

atom probes its local environment while

nanoscale techniques position it within

that environment. Here, the probe is the

cobalt atom and the STM tip moves it

across the copper surface. The atom

responds to the surface potentials

through its lateral motion, which is

reflected in the measured tunneling

current. This allows measurement of the

binding site map of the copper surface

through observation of the dynamical

response of a single scanned atom to

its environment. We are planning

additional experiments using atombased metrology.

CONTACT: DR. JOSEPH A. STROSCIO

(301) 975-3716

joseph.stroscio@nist.gov

Model

Left of center

Right of center

0.0 0.2 0.4 0.6 0.8 1.0 Normalized Distance from Center

Figure 2. SEM image of a silicon nanopillar,

along witli a SEMPA image of tine epitaxial,

cobalt tfiin-film disk at tine top of tfie pillar

The SEMPA measurement shows a geometrically

constrained domain wall whose width varies

with radial distance.

Geometrically Constrained

Magnetic Nanostructures

Small, patterned, magnetic thin-film

structures play a critical role in emerging

magnetoelectronic technologies, which

range from nonvolatile random access memories to magnetic field sensors. One potential advantage of miniaturizing these devices is that the size and

geometry of the patterned structure may

be used to shape the internal magnetic

nanostructure and thus control the

device operation. Imaging this internal

nanostructure is a measurement challenge, since the structures consist of

only a small amount of magnetic

material and can easily be perturbed by

conventional magnetic imaging methods

such as Magnetic Force Microscopy

(MFM).

5
ELECTRON AND OPTICAL PHYSICS DIVISION

In collaboration with the University

of Cambridge Thin-Film Magnetism

Group we have used our SEMPA facility

to noninvasively image the magnetic

nanostructure of epitaxially grown thinfilm Co disks. Isolated, micrometersized Co disks were grown by depositing

a several-nanometer-thick Co film onto

a Si substrate with etched circular pillars. Unlike bulk Co, these epitaxially

grown Co thin films have a cubic crystal

structure that leads to a four-quadrant,

closed-flux domain structure, characteristic of a film with cubic anisotropy.

The SEMPA images (e.g.. Fig. 2)

showed how the internal magnetic

nanostructure of these disks depends

critically on the size and shape of the

element. Magnetic domain wall widths,

for example, do not depend on sample

geometry in bulk ferromagnets. But in

these structures the domain walls are

geometrically constrained by the significant shape-related magnetostatic energies, and the wall widths vary dramatically with radial distance from the

magnetic vortex core.

CONTACT: DR. JOHN UNGURIS

(301) 975-3712

john.unsuris@nist.gov

Imaging Magnetic Sensors

Recent advances in thin-film and multilayer magnetism offer the exciting possibility of creating a new generation of

magnetic sensors that are small, inexpensive, and as sensitive as currently

used, more cumbersome sensors such

as SQUIDs. Development of this new

generation of sensors requires understanding and control of the magnetic

nano-structure, in order to enhance

sensitivity and eliminate potential

sources of magnetic noise.

oommf)

2 4 6 X [MM]

Figure 3. SEMPA image of a zigzag magnetic

sensor element, compared witli tlie OOMMF

micromagnetics simulation. Line scans through

the centers of the elements show the magnitude of the magnetic oscillations.

We are working with NIST magnetics

groups in EEEL, MSEL, and ITL to test and measure possible new materials and

devices for use as sensors. One potentially useful device is a zigzag-shaped magnetic sensor developed by EEEL. The

device's magnetic sensitivity is based on

anisotropic magnetoresistance (AMR),

and therefore requires the magnetization

to be tilted with respect to the current

passing through the device. In the

zigzag sensor, the shape anisotropy

forces the magnetization to tilt relative

to the current.

We have used SEMPA to measure how

well various zigzag geometries accomplish this angular biasing and to look

for potential sources of magnetic noise.

(See Fig. 3.) SEMPA imaging is especially useful since it not only images the

magnetization directly, it provides a

quantitative measurement of magnetization directions that can be compared to

the results of micromagnetic calculations. The SEMPA images also reveal

potential magnetic trouble spots such as

trapped magnetic singularities, which

can interfere with reproducible magnetic

response, as well as defects that can produce magnetization-related noise.

Work is currently underway to allow

imaging of electrically active magnetic

sensors, which will allow a better understanding of noise sources and failure modes in real devices.

CONTACT: DR. JOHN UNGURIS

(301) 975-3712

john.unguris@nist.gov

Current Induced Magnetic

Switching

In a magnetic multilayer, changing the

relative orientation of the magnetizations of two layers changes the current

flowing through the multilayer. This

effect, called giant magnetoresistance, is

used in magnetic sensors, magnetic ran- dom access memory (MRAM), and read

heads in magnetic disk drives. An

inverse effect, where the current changes

the magnetic configuration, is being

studied for possible applications. In this

case, a current passing through a multilayer exerts a torque on the magnetizations of different layers causing the

magnetizations to rotate.

Large enough currents passing through

such multilayers can switch the magnetizations of the layers between parallel and

antiparallel, or cause one to rapidly precess around the other layer. If the size of the current necessary to reverse magnetizations can be reduced sufficiently,

spin-transfer torques could provide a way to switch bits in MRAM. In other

devices, it should be possible to make

current-controlled oscillators.

6
ELECTRON AND OPTICAL PHYSICS DIVISION

We have developed quantitative models

for these spin-transfer torques to help

the development of devices based on

this effect. (See Fig. 4.) In particular, we

recently developed an analytic formula

for the torque as a function of the

device geometry and the magnetic configuration. Such a formula will allow

rapid simulation of prototypes for

device optimization.

(J

r

Co

Fisure 4. Electron diffusins near a ferromasnetic

interface. The spin of tine electron diffusing in

the copper has its direction changed when it

scatters from a cobalt interface with an in-plane

spin wave.

We have also shown how spin-transfer

torques can cause a magnetic instability

even with a single ferromagnetic layer.

This effect was first seen in point-contact experiments and later in more

device-like, lithographically fabricated

nanopillars. We explained how in-plane

inhomogeneities in the magnetization

lead to the observed instabilities. We are

presently studying the effect of these

inhomogeneities on more typical device

geometries.

CONTACT: DR. MARK D. STILES (301) 975-3745

mark.stiles@nist.gov

End States in OneDimensional Chains

The abilities to fabricate structures on

the nanoscale and to measure their electronic properties present the opportunity to discover new phenomena. We have

observed a new kind of electronic state

at the ends of a one-dimensional nanostructure. This "end state" is a direct

consequence of the lower dimensionality

of the structure. Such end states can be

thought of as zero-dimensional analogs

to two-dimensional states that occur at

the surface of a crystal.

In fabricating these structures, we

exploit the self-assembly of atom chains

that occurs when we deposit gold on

stepped silicon surfaces at elevated temperatures. Rows of atom chains of varying length can be seen in the STM

images of Fig. 5, which are of the same

area but measured at opposite polarity.

The chains in the upper panel, measured at a sample potential of +0.5 V,

appear shorter than the chains in the

lower panel, measured at a sample

potential of -1.0 V, as emphasized by

Figure 5. STM images of one-dimensional atom

chains on Silicon, showing empty states (upper

panel) and filled states (lower panel). End

states cause the chains to appear shorter in the

upper panel.

the white box around a seven-atom

chain. Such a polarity contrast in STM

suggests an underlying difference in the

density of states for the empty and filled

states near the ends of the chains,

indicating the presence of end states.

To characterize this new kind of electronic state, we made spatially resolved

scanning tunneling spectroscopy measurements along finite chains to map

the density of states. These measure- ments reveal quantized states that form

in isolated chain segments. Furthermore, a transfer of spectral weight from

the filled to the empty states over the

atoms at the ends of the chains is

directly attributable to the formation

of end states.

These end states cannot be described

by a simple particle-in-a-box model for

states along the chains. A comparison

to a tight-binding model demonstrates

how the formation of end electronic

states transforms the density of states and the quantized levels within the

chains. The end states effectively lower

the energy levels of the filled states within the chains, suggesting a possible

driving force for their formation. As a

further confirmation of the tight-binding model and the end electronic effects, we calculated STM topography profiles

at positive and negative biases and

reproduced the experimentally observed

contrast at the end atoms in Fig. 5.

CONTACT: DR. DANIEL T. PIERCE

(301) 975-3711

daniel.pierce@nist.sov

7
ELECTRON AND OPTICAL PHYSICS DIVISION

he second strategic

focus is the development of

metrolosy for extreme ultraviolet (EUV) optics, the maintenance of national primary

standards for radiometr/ in

the EUV and adjoinins

spectral resions, 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 synchrotronbased, national primary standard for

source-based optical radiometry.

The Division has longstanding responsibility for the national primary radiometric standards in the EUV region of the

spectrum. EUV radiation is an important tool for determining the electronic

structure of materials, diagnosing plas- mas, 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 metrology 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 (up to 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.

ACCOMPLISHMENTS

Characterization of Damaged

EUV Condenser Optics

EUV lithography is a candidate process

for producing the next generation of

semiconductor devices, with feature sizes

that are 50 nm or less. One of the outFisure 6. Measured EUV reflectivity over surface

of a condenser optic, and an SEM imase of a

small resion showins the striations associated

v/ith the erosion of the multilayers.

standing issues that must be solved in

order for EUV lithography to proceed

to commercialization is the durability

of condenser optics, which collect and

direct the radiation from its source. EUV radiation is produced by hightemperature plasmas generated by electrical discharges or high-intensity lasers. These plasmas emit not only EUV radiation, but also broadband radiation,

electrons, and ions. This hostile environment can damage the condenser optics

and reduce its lifetime, which must be

months long for EUV lithography to

be commercially viable.

In collaboration with SEMATECH

we have analyzed one such condenser

element, which had operated for three

months in the Engineering Test Stand

at Sandia National Laboratories. This

condenser had a Mo/Si multilayer reflective coating, and it was used to collect

the radiation from a laser-produced Xe

plasma. After exposure to the plasma,

the optic was covered by a visible array of erosion-associated striations. The

origin of these stripes was a mystery.

As shown in Fig. 6, the reflectivity of

the optic was measured at the NIST/

DARPA EUV facility while die surface

composition and structure were mea8
ELECTRON AND OPTICAL PHYSICS DIVISION

sured using the Electron Physics Group's

SEM, AUGER, and AFM faciUties. This combination of tools allowed an

understanding of the optic's EUV reflectivity in terms of the nanoscale compositional and structural properties of the

surface.

The measurements showed that the lowreflectance stripes were due to periodic

stripes of increased roughness, and that

each stripe corresponded to one additional Mo/Si bilayer of the multilayer

coating being removed.

CONTACT: DR. SHANNON HILL (301) 975-4283

shannon.hill@nist.gov

Long-Term Endurance Testing

of EUV Projection Optics

The lithography tool that exposes the

wafers in the patterning process is called

a stepper. It consists of a radiation

source and its condenser optics to illu- minate the patterning mask, projection

optics to image the mask onto a resistcoated wafer, and a mechanical device

that aligns the wafer to the mask.

Although the system is operated under

vacuum, there is still a significant

amount of water and hydrocarbons

present. These materials interact with

the EUV and cause the performance of

the optics in the system to degrade. The

effect is significant, and it is a critical

factor in determining the operational

lifetime of a stepper.

NIST recently commissioned a beamline on SURE III dedicated to longterm exposure studies of EUV multilayer projection optics. It contains a spherical, 75 mm diameter, Mo/Si multilayer

Fisure 7. Simulated reconstruction of a polymer

sample, as imased by transmission electron

microscopy. Length of bar in lower right is 1

micrometer

focusing mirror. This images the EUV

beam onto a sample optic with a spot

size of approximately 0.6 mm x 0.8 mm

(FWHM). The sample chamber is separated from the mirror chamber with a

removable, 0.3 \im thick beryllium foil.

It filters out long-wavelength radiation

and allows a differential vacuum

between the sample chamber and SURF.

This permits exposure of the sample

optics to EUV radiation in the presence

of larger partial pressures of water and

other species, to simulate the environments present in EUV steppers.

CONTACT; DR. CHARLES S. TARRIO

(301) 975-3737

charles.tarrio@nist.gov

Nanoscale Chemical Imaging

We are developing state-of-the-art measurement techniques and algorithms to

acquire three-dimensional, chemically

resolved images of nanoscale samples,

using transmission electron microscopy.

We seek an enhanced, fiandamental

understanding of the probe-sample

interactions relevant to electron

microscopy, including incoherent and

coherent scattering, electron energy loss

spectroscopy, and x-ray generation and

propagation. In this joint project, we

use instrumentation to acquire data in

the Chemical Science and Technology

Laboratory and investigate reconstruction algorithms to form the images with

the Information Technology Laboratory.

Earlier work led to reconstructions of

integrated circuit interconnects using an x-ray microscope, as well as to the

detailed observation of M x-ray absorption edges in tantalum and tungsten.

More recently, the possibility of per- forming reconstructions on polymer

samples up to 8 micrometers in size

using a scanning transmission electron

microscope has been demonstrated in

simulation. The total size is noteworthy

because nearly all tomographic reconstructions use smaller samples to avoid

the multiple-scattering regime. Here it

is shown that multiple scattering can be accounted for mathematically, and

reconstructions may be performed, even in the presence of a few scattering

events. A simulated reconstruction

appears in Fig. 7.

CONTACT; DR. ZACHARY H. LEVINE

(301) 975-5453

zachary.lcvine@nist.gov

Absolute Radiometry at

SURF III

The SURF III facility recently became

the source of the most accurate ultraviolet lamp calibrations in the world.

The SURF upgrade in the mid-1990s

was motivated by the need to improve

our source calibration capabilities in the

ultraviolet spectral region. To accomplish this, the magnet system had to be

improved, which in SURF's case meant

replacement of the coils, the steel used

in the back legs, the power supply, and

the control system.

9
ELECTRON AND OPTICAL PHYSICS DIVISION

Recently these immense improvements

were put to the test during a Consultative Committee for Photometry and

Radiometry (CCPR) key comparison

between several national measurement

institutes, piloted by the German

Physikalisch-Technische Bundesanstalt

(PTB). This comparison focused on the

calibration of specially prepared deuterium lamps in the spectral range from

200 nm to 350 nm.

NIST was the sole laboratory to employ

synchrotron radiation in the calibration

process, leading to the smallest uncertainties among all participating laboratories. The uncertainty achieved at SURF

was 0.5 % (coverage factor k = 1) for

the entire spectral range.

Figure 8. Monochromator during alignment.

For this comparison, a detection system,

consisting of a monochromator, a diffusing device, and a photodetector, was

calibrated against SURF, utilizing the

calculability of synchrotron radiation in conjunction with our accurate monitoring of its operational parameters.

Figure 8 shows a monochromator

during alignment. Once the system was

calibrated, it could be used to determine

the spectral irradiance of a lamp.

CONTACT: DR. UWE ARP

(301) 975-3233

uv^e.arp@nist.3ov

he third strategic focus is metrolosy for coherent matter-wave and quantum information processins devices.

Coherent Matter-Wave

and Quantum

Information

Processing Metrology

INTENDED OUTCOME AND

BACKGROUND

This program provides measurements

and data to enable the development of

ultracold atom technology, in particular

the use of coherent matter waves in sensors, atom interferometers, and quantum information processing devices.

The Division maintains two efforts in

this area, one theoretical and one experimental. The theoretical program is

focused on quantitative modeling of

degenerate quantum gases, with particular attention to the dynamics of BoseEinstein condensates subject to external

forces, 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 program develops

deterministic atom-delivery systems, i.e.,

devices that can deliver precisely one atom to a predetermined location, on

demand. In addition, the Division is developing a testbed for quantum communication systems, together with the

Atomic Physics Division and the

Information Technology Laboratory.

ACCOMPLISHMENTS

Characterization of

"Atom-on-Demand" Source

Recent developments in our laboratory

have led to a new source of atoms that is almost completely deterministic: single

atoms can be made available at a high

rate with near unity certainty. Such a

source has applications not only in quantum information processing, where

single atoms can be used as qubits, but

also in nanotechnology, when doping of

nanostructures reaches the level where

each nanostructure contains only a countable number of dopants.

In order to proceed to the next step in our research program, which will be to

extract atoms from our source and

demonstrate controlled deposition, we

have conducted a number of studies to

characterize our source. These have

involved a detailed analysis of all the

experimental parameters that determine

the performance of the source, and also

real-time photography of single atoms.

The detailed analysis has allowed us to implement Monte Carlo simulations

that show extremely good agreement

with experimental observations of such

parameters as the single-atom probability and the single-atom extraction success

rate. The photography, using a high-sensitivity CCD camera (Fig. 9), has given

us the ability to investigate the spatial

properties of our source, which will

prove crucial in extracting, transporting,

and depositing the single atoms with

high spatial resolution.

CONTACT: DR. JABEZ J. MCCLELLAND

(301) 975-3721

jabez.mcclelland@nist.gov

10
ELECTRON AND OPTICAL PHYSICS DIVISION

Random numbers of atoms.

JODaaDaDaaDDOOODaoDaDaoDDDoaDDOooDDOoaDDa

• • •

Single atom

-[

oncdemand...

Fisure 9. Real-time •'r

images of single atoms in an atom-on-demand source. Without feedback, tfie number of atoms is random, fluctuating between one, two, and three. With feedback, there is always just a

single atom in the source.

Resonant Atom-Molecule

Mixtures in QuantumDegenerate Gases

Cooling fermionic, atomic gases to quantum degeneracy, in conjunction

with the ability to directly control the

interatomic interactions through magnetic-field-tunable Feshbach resonances,

has opened the door to a detailed study

of the crossover between BardeenCooper-SchriefTer superfluidity and

Bose-Einstein condensation of diatomic

molecules in an atomic Fermi gas.

A Feshbach resonance can be used to

couple atom pairs into a bound molecular state, thereby creating bosonic

dimers in the gas. Under suitable conditions, these dimers can undergo BoseEinstein condensation. The BCS-BEC

crossover is a cornerstone problem of

condensed matter physics, due in large

part to its importance in the understanding of high-temperature

superconductivity.

We have studied the equilibrium phase

diagram of atom-molecule mixtures in a

simple model under experimentally

relevant conditions. A finite fraction

of molecules persists for energies above

dissociation threshold. At high temperatures this is ascribable to a detailed balance between atomic association and

molecular dissociation in the gas, while

in the quantum-degenerate regime Pauli

blocking stabilizes molecular states embedded in the continuum.

Recent experiments found a significant

discrepancy between theory and experiment concerning the dependence of the

dimer condensation threshold on the

temperature of the gas. We found that

this discrepancy disappeared when the

thermodynamic evolution of the system was taken into account. In particular,

the temperatures measured in the exper- iments are those of the initial state of

the Fermi gas; as one sweeps through

the Feshbach resonance, the temperature

of the gas changes. The conditions of

the experiments are believed to be adiabatic, which means that the system

should follow a trajectory of constant entropy in the thermodynamic phase

diagram. Examples of such trajectories

are shown in Fig. 10. These demonstrate

that assuming fixed temperature of the

gas would overestimate the condensate

threshold temperature.

CONTACT: DR. CHARLES W. CLARK

(301) 975-3708

charles.clark@nist.gov

1.0

Q.

0.6

0.4

0.2

0.0

-4 -2 0 2 4 Resonance Energy [eRes^e^B^p)!-4 -2 0 2 4 Resonance Energy [eRes^C^B^F)!

Figure 10. Phase diagrams of atom-molecule mixture showing the molecule fraction (A) and condensate fraction (B) as a function of temperature and resonance energy, £^^^, in units of the Fermi temperature and Fermi energy, respectively Lines indicate contours of constant entropy, which are the trajectories followed by the system under adiabatic variation of the threshold energy.

11
'

'''

GOAL ATOMIC PHYSICS DIVISION

TO DETERMINE ATOMIC "^^^ strategy ofthe Atomic Physics Division is to develop and apply atomic

_ ^ . physics research methods, and particularly the interaction between atoms and

PROPERTIES AND ^ ^ r j

electromagneticfields, to achieve fundamental advances in measurement sciINVESTIGATE , /• • / • / / , /

• , ence—some at the quantum Limit—relevant to industry and the technical

FUNDAMENTAL QUANTUM community, and to produce and critically compile physical reference data.

INTERACTIONS - .

Ihe first strategic

element is to advance the

physics of electromasneticmatter 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.

Lisht-Matter

Interactions and

Atom Optics

INTENDED OUTCOME AND

BACKGROUND

This strategic element focuses on the

physics 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 and applied

studies, such as developing measurement

techniques for biomolecular systems and

developing a quantum information

processor. A strong theoretical-experimental collaboration is aimed at interpreting experimental results and providing guidance for new experiments.

The development of laser cooling and

trapping techniques allows exquisite

control over the motion of atoms. Such

control has been exploited to build more

precise atomic clocks, gravity meters,

and gravity gradiometers. 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.

Our research includes theoretical and

experimental projects that contribute to

the understanding and exploitation of:

Bose-Einstein condensation of neutral

atoms; matter-wave optics; optical and

magnetic control of trapped, ultracold

atom collisions; advanced laser cooling

and collision studies for atomic clocks;

the quantum behavior of atoms in optical lattices, including in low dimensionality; the superfluid to Mott-insulator

quantum phase transition; quantum

information processing; quantum

computing architectures; and optical

characterization and manipulation of

single molecules, biomolecules, and

biomembranes.

ACCOMPLISHMENTS

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

quantum gases such as Bose-Einstein

condensates or mixtures 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 fundamental physics, condensed matter (solid

state) physics, atomic clocks, and

quantum information.

L

12
We have applied quantum mechanical

models to quantitatively characterize

such resonances and to develop simple

physical models for understanding

them. These have been applied to give

good agreement with data and predictive power for bosonic species ^^Rb (see

Fig. 1) and '^^Cs, and for fermionic

species "^Li and ^'^K. We have also initiat- ed studies on optically induced scattering resonances for laser control of quantum gases of alkaline earth species such

as Ca or Sr, which are of great interest

for next-generation atomic clocks.

CONTACT: DR. PAUL S. JULIENNE

(301) 975-2596

pauLjulienne@nist.sov

100

E

^

0.1

0.01

Experiment — Theory -

15.6 15.8 16.0 16.2 16.4

IVIagnetic Field (B) [ml]

Fisure 1 . Lifetime of the tunable, molecular bound state of the ^^Rbg dimer as a masnetic

field B is varied near a scattering resonance at

15.2 mT. The rapid increase in lifetime is due

to the dramatic increase in the size of the

v^eakly bound atom-pair, to hundreds of

nanometers, as the field gets closer to the resonance value.

Figure 2. Time sequence of video microscopy images showing two liposomes, brought into contact

with optical tweezers and induced to fuse by an optical scalpel, a pulsed ultraviolet laser focused on

the contact point, which initiates the fusion (a). Images (b), (c), and (d) were taken 132 ms, 264 ms,

and 528 ms later, respectively

Spectroscopy of Na2

Molecules in the Lowest

Triplet State

We have used the technique of twocolor photoassociation spectroscopy

(two colliding atoms absorbing photons

to create a diatomic molecule) to improve the spectroscopy of the lowest

triplet state of the Na, molecule. The

spectra obtained represent a factor of

1 000 improvement in resolution over

the previously obtained spectra of this

state, and include a number of previously unobserved vibrational levels, as well

as unresolved hyperfme and fine structure. This knowledge has altered our view of the angular momentum coupling scheme that must be used to

represent this state of the molecule.

Knowledge of the interaction potentials

between two sodium atoms, at the level of detail that can be obtained by

photoassociation spectroscopy, is

required to predict the behavior of this

prototype system of two colliding, effectively single-electron atoms. Improved

theory in this area is necessary for

understanding many experiments in atomic and molecular physics, and is

especially pertinent for current studies

of atomic and molecular Bose-Einstein

condensates.

CONTACT: DR. PAUL D. LEH

(301 ) 975-6559

paul.lett@nist.gov

Optical Manipulation of

Nanocontainers for

Biotechnology

In collaboration with researchers in CSTL and CARB, we are developing

optical techniques for manipulating

nanocontainers (containers with femtoliter volumes of fluids), to perform

ultrasmall volume chemistry and to

isolate and sort single molecules.

We are currently investigating three systems, liposomes, polymersomes, and

hydrosomes, for use as nanocontainers.

Liposomes and polymersomes are closed

structures composed of a lipid and poly- mer membrane, respectively, typically

about 1 0 micrometers in diameter. The

membrane acts as a barrier to separate an aqueous interior environment from

an aqueous exterior environment.

Hydrosomes are micrometer-sized, surfactant-stabilized water droplets that

reside in a fluorocarbon environment.

The techniques we use include optical

tweezers, for trapping and remotely

moving the nanocontainers, and an

"optical scalpel," for opening membranes in order to induce fusion of

liposomes and polymersomes. (See

Fig. 2.) In all three systems, we are

able to bring together two similar

nanocontainers using optical trapping

and to subsequently fuse them together,

allowing their contents to mix.

13
ATOMIC PHYSICS DIVISION

We have demonstrated the use of hpo- somes and hydrosomes in performing

controlled, elementary chemical reactions. We are currently investigating the

application of these nanocontainers for

single-molecule studies and singlemolecule sorting.

CONTACT: DR. KRISTIAN HELMERSON

(301) 975-4266

kristian.helmerson@nist.gov

Neutral-Atom Quantum

Information

Single atoms can act as qubits for quantum information (QI) using, for example, the internal hyperfine and Zeeman

states as the qubit states. Our approach

to neutral-atom QI is to hold and

manipulate the atoms using laser fields

for trapping and transporting. An optical lattice provides a natural register for atomic qubits. A BEC loaded adiabatically into an optical lattice provides,

potentially, millions of qubits initialized

in their ground states, since the BEC,

or at least the condensed fraction, is

initially in the ground state.

If a noninteracting BEC is slowly loaded

into an optical lattice, the typical result

is that the coherent wavefunction of

each atom is spread across all the available lattice sites, so that there is a statistical (Poissonian) fluctuation in the

number of atoms in any given site. If,

however, there are repulsive interactions,

at some lattice depth the competition

between tunneling and the on-site

repulsive interaction favors the ground

state being one (or some fixed number

of) atom(s) per lattice site. This is a phase transition known as the Mott

insulator transition because the system

goes from being superfluid (at large

tunneling rate) to insulating (at small

tunneling).

We observe the phase transition for Rb

atoms in a three-dimensional optical lattice by looking at the diffraction pattern

formed by the atoms upon release from

the lattice. As shown in Fig. 3, wellresolved diffraction indicates phase

coherence across the lattice, and therefore an uncertain atom number in each

site. The disappearance of the diffraction

pattern is characteristic of a fixed number per site, and therefore an uncertain

phase difference from site to site, indicative of being in the insulator state.

CONTACT: DR. WILLIAM D. PHILLIPS (301) 975-6554

william.phillips@nist.gov

Typical Scan Time [ms]

Figure 3. As the 3-D lattice depth is

increased, the tunneling between lattice sites

decreases. At a lattice depth of around 10

recoil energies, the system undergoes the

Mott transition, and the diffraction pattern

disappears. The transition is reversible, and

the diffraction reappears when the lattice

depth is reduced.

^^i^e second strategic

element is to advance

measurement science at tine

atomic and nanometer scale,

focusins on precision optical

metrolosy, quantum devices,

nanoscale plasmas, and

nanooptical systems.

Nanoscale and

Quantum Metrology

INTENDED OUTCOME 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, 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 sys- tems 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

14
ATOMIC PHYSICS DIVISION

create nanooptics structures that will be

needed in emerging quantum and

nanoscale technologies.

Experiment is used to develop new precision measurement tools for this

regime, to collect precise data essential

for the applications mentioned, and to

further the understanding of these systems. We have developed precision

metrology to make accurate displacement measurements to subatomic

dimensions by use of frequency combs

locked to a cesium atomic clock. We

have made the precise measurements of

the refractive index of water needed by

the semiconductor industry to develop

immersion lithography for sub- 100 nm

optical lithography. And we are now

expanding our expertise by beginning to probe the nanooptics and nanomechanical properties of nanoscale and quantum-coherent systems.

ACCOMPLISHMENTS

Designing tlie 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

nanosystems at the nano/molecular

interface are being carried out. These

systems include nanocrystals, self-assembled dots, nanodot arrays and solids,

molecular electronics, and bio/nanohybrids. These simulations provide

benchmarks for precise experimental

Fisure 4. Field within and around a 60 nm

radius sold nanoring. Enhanced fields inside

the nanoring vvould make the nanoring a useful container for precision nanoexperiments.

tests of the atomic-scale 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.

Nanoscale simulations of optical fields

near nanosystems are also being carried

out. Results are being used to design

nanoprobes and nanocavities, as shown

in Fig. 4, for use in precision nanooptics

metrology. Results are 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 transport of excitations in

quantum devices and in the metrology

of these devices.

CONTACT: DR. GARNEH W, BRYANT

(301) 975-2595

garnett.bryant@nist.gov

Subatomic Displacement

Measurements

We are concluding our program to improve the accuracy of Michelson and

Fabry-Perot interferometry for measuring displacements of macroscopic

objects with subatomic precision. Our

work in Fabry-Perot interferometry is

the realization of the idea first put forth

by Zoltan Bay at NBS in 1970, of using

a microwave measurement of the mode

spacing within a Fabry-Perot cavity to measure displacements free of the systematic error induced by diffraction.

In our most recent implementation of

Bay's idea, as shown in Fig. 5, we probe

two adjacent modes of a variable-length

Fabry-Perot cavity with red light from a HeNe laser at 633 nm, and another

mode with orange light from a HeNe

laser at 612 nm. A precise measurement

of the mode spacing using the light at 633 nm allows us to determine the exact number of modes in the 16 THz interval between the red and orange lasers. We then beat light from the HeNe lasers

against light from a visible frequency

comb that is locked to a cesium atomic

clock. The resulting measurements of

the cavity length are not compromised

by diffraction. They are related directly

to the definition of the second, and by

extension, the meter.

15
ATOMIC PHYSICS DIVISION

We are now turning our focus to the

metrology needs of microscopic systems

themselves, in particular, microelectromechanical (MEMS), nanoelectromechanical (NEMS), and nanooptical

systems. Precision optical and quantum

optical metrology will be exploited to probe individual nanoscale and,

possibly, quantum-coherent systems.

CONTACT: DR. JOHN R. LAWALL

(301) 975-3226

john.iav/all@nist.3ov

From Comb

From CW Lasers

Collimator

Fiber 3 dB Coupler

Avalanche

Photodiodes

Figure 5. Setup to measure frequency difference of 1 6 THz between lasers at 61 2 nm

and 633 nm. Light from the CW lasers is beat

against light from a visible frequency comb

in a fiber 3 dB coupler After collimation, the

red and orange components are separated

with a grating, and the beats of the CW lasers

with adjacent comb lines are measured on

avalanche photodiodes.

Optical Properties in Support

of UV Lithography

In late 2002, the semiconductor lithography industry began an effort to

explore the feasibility of developing

immersion lithography as a method to extend optical lithography into the sub100 nm feature-size region. In this technology, an immersion fluid is inserted

between the fmal lens of a 193 nm or 157 nm lithography projection system

and the silicon wafer, thus dividing the

diffraction-limited feature size by the

refractive index of the fluid. However,

at that time there existed no accurate measurements of the key optical properties of water, the principal candidate

193 nm immersion fluid.

To address this need, the Atomic Physics

Division and the Optical Technology

Division teamed up to develop a UV

fluid refractive index measurement facility. By March of 2003, the project delivered the first accurate measurements of

the refractive index of distilled water at 193 nm to five decimal places, sufficient

for system design. The project also

delivered other key optical properties of

water, including the dependence of the

index on wavelength, temperature, pressure, and gas and impurity content.

Immersion lithography systems using

water at 193 nm are being designed and

built around the world, relying on these

measurements as key design parameters.

The project has also characterized the

optical properties of other fluids with

significantly higher 1 93 nm indices than

that of water, which may potentially

enable further resolution increases. The

semiconductor industry now has a parallel effort to explore immersion lithography at 157 nm. The project has also

delivered the first measurements of the

key optical properties of the candidate

immersion fluids in this vacuum

ultraviolet region.

CONTACT: DR. JOHN H. BURNEH

(301) 975-2679

John.burnett@nist.30v

Figure 6. Scanning tunneling microscope image

(32 nm x 32 nm) of a 9 nm mound, two

atomic layers high, created by the impact of a

single Xe'*^* ion on the Au(1 1 1 ) surface. The

mound has relaxed to a perfect hexagon, and

the "herring-bone" reconstruction in the background has rearranged around the mound to

minimize surface energy.

Nanometrology of HighlyCharged-lon Collisions with

Neutral Matter

Highly charged ions (HCIs) constitute a unique and exotic form of matter, typically out of human reach, but they can

be created and studied within the NIST

Electron Beam Ion Trap (EBIT) facility. When neutral matter is exposed to HCIs, the intense electronic interaction

produces extreme conditions that allow

us to probe properties of both participants, including processes of x-ray emission, charge exchange, and surface damage (see Fig. 6). By coupling HCIs with

surface science techniques like scanning

tunneling microscopy, we are able to

observe electronic and morphological

changes at atomic length scales and to probe the fundamental connections of

atomic and solid state physics.

This unique combination of capabilities

has been used to diagnose HCI damage

to advanced Mo/Si multilayer mirrors,

used for extreme ultraviolet (EUV)

lithography. Tunneling spectroscopy and

EUV reflectivity measurements have

revealed that the EUV-source ions cause

approximately ten times more damage

if they neutralize on the oxidized ruthenium capping layer of the optics than

if they neutralize prior to collision.

These measurements highlight the

broader need for providing critical components with protection from HCIs

16
ATOMIC PHYSICS DIVISION

when operating in close proximity to

plasmas. Experiments currently underway on gold surfaces are designed to determine whether high-electron-density

materials exhibit less damage than insulating and oxidized materials, currently

used for critical components.

CONTACT: DR. JOSHUA M. POMEROY

(301) 975-5508

Joshua. pomeroy@nist.sov

^^he third strategic element

is to produce reference

data on atomic structure, to

critically compile reference

data for scientific and technolosical applications, and to

develop techniques to apply

the data to further the understandins of important plasma

devices.

Critically Evaluated

Atomic Data

INTENDED OUTCOME AND

BACKGROUND

The objective of this strategic element

is to critically compile fiindamental

constants and atomic spectroscopy data

from the far infrared to the x-ray spectral regions. We disseminate these reference data on the Physics Laboratory

website, produce high-quality data for

urgent scientific or technological needs,

and resolve discrepancies in the body

of the data. 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. The

Atomic Spectra Database on our website

now dispenses about 100,000 downloads (answers) per month, up from

80,000 only two years ago. The

principal users are plasma physicists,

crystallographers, astronomers, lighting

engineers, and spectrochemists.

The newest version of the Atomic

Spectra Database significantly reduces

internal inconsistencies between atomic

energy levels and atomic transition frequencies by merging older databases and

resolving and removing inconsistencies.

However, the databases remain far from

complete, and the quality of the data

available in the literature from which

the databases are built is still uneven. The current versions of our databases

are not sufficiently reliable for some

fields of science and technology, and

needs for such reference data are continuously growing. Our scientists focus

their resources on the most urgent needs

of the user communities.

ACCOMPLISHMENTS

New Generation of Atomic

Spectra Database

Version 3.0 of the NIST Atomic Spectra

Database has been released, which contains many new data and interface

improvements. Information is given for

the wavelengths, energy levels, transition

probabilities, Lande ^-factors, and

ionization energies of many atoms and

ions. The Database now contains evaluated data for over 100,000 spectral lines and over 70,000 energy levels.

This new version is based on a relational

database management system, which

assures a high level of consistency and

integration of the data, as, for example,

for the information on the lines and levels of a particular atom. New interface

features include instant access to bibliographic references, dynamic transition

(Grotrian) diagrams, online generated

plots for spectral line identification, and

online generated plots for Saha/LTE

plasma emission spectra for arbitrary

electron temperature and density.

CONTACT: DR. JOSEPH READER

(301) 975-3222

joseph.reader@nist.gov

2002 CODATA

Recommended Fundamental

Constants

Based on work of the Fundamental

Constants Data Center of the Division,

the Committee on Data for Science

and Technology (CODATA) has recom- mended for international use a new set of values of the fundamental physical

constants and energy-related conversion

factors.

The new set of values, termed the

2002 CODATA recommended

values, became available to the public on December 8, 2003 at

http://physics . nist. gov/constants

A detailed paper on the data selection

and methodology of the adjustment is due to be published in the Reviews

of Modern Physics.

17
ATOMIC PHYSICS DIVISION

This review of the fundamental constants provides recommended values and

their associated uncertainties, updating

the last review of 1998. Since then, new

methods have become competitive for

the determination of the Planck constant h, the fine-structure constant a, and the relative atomic mass of the electron m^; and there has been a dramatic

improvement in the measurement of the

Newtonian constant of gravitation G.

Two noteworthy additions in the

2002 adjustment are recommended

values for the bound-state RMS charge

radii of the proton and deuteron, and

tests of the exactness of the Josephson

and quantum-Hall-effect relations

icTj = 2e/h and R^^ = h/e^, where and

Ry^ are the Josephson and von Klitzing

constants, respectively, and e is the

elementary charge.

This work has met with immediate

acceptance by the scientific community.

The new values were published in the

online August 2004 Physics Today

Buyers Guide and in the 85"^'^ edition of

the CRC Handbook of Chemistry and

Physics for 2004-2005.

CONTACT: DR. PETER J. MOHR

(301) 975-3217

peter.mohr@nist.gov

Precision Measurement of

Reference Wavelengths for

1 93 nm Lithography

Some of the newest tools for microlithography are based on the ArF excimer

laser, which emits radiation that can be

tuned over a narrow band near 193 nm.

In order to design systems that focus the

laser light onto substrate surfaces, lens

designers must know the index of refracWavelength [nm]

193.8 193.7 193.6 193.5 193.4 193.3 193.2

>- 100

COc

m

w

01

51600 51650 51700 51750

Wavenumber [cm"'']

Fisure 7. High-resolution spectrum of iron,

germanium, and platinum, showing lines

measured as wavelength standards for

lithography at 193 nm.

tion of the optical materials to a high

degree of accuracy. Since the index of

refraction varies rapidly in this spectral

region, it is essential that the ArF laser be stabilized at an accurately known

wavelength.

In one method used to determine the

laser wavelength, the laser is observed

along with reference spectra of iron,

germanium, and platinum, excited in hollow cathode discharge lamps. The

ArF laser wavelength is determined by

interpolation among the reference lines. However, until now the wavelengths of

the reference lines were not known

sufficiently well to obtain the desired

accuracy for the laser wavelength.

By using a Fourier transform spectrometer optimized for use in this region of

the ultraviolet, we have made precise

wavelength measurements for seven lines of iron, germanium, and platinum that

span the tuning range of the ArF laser.

(See Fig. 7.) An overall relative uncertainty of 3 X 10~^ was achieved. These

results will serve to determine the ArF

laser wavelength to the required accuracy. The experiment was conducted in

collaboration with an excimer laser manufacturer that supplies lasers for

microlithography applications, and the

results have been incorporated in a commercial laser system.

CONTACT: DR. GILLIAN NAVE

(301) 975-4311

gillian.nave@nist.gov

X-Ray Probes of Metal-Hallde

Discharge Lamps

There are about one billion plasma light

sources in service in the United States, consuming an estimated 2 exajoules

(600 billion kilowatt hours) of electrical

energy annually. These sources are principally fluorescent lamps and metalhalide discharge lamps. In the past,

metal-halide lamps were used mainly for

high-intensity lighting of large spaces. Now, because of their high brightness

and energy efficiency, they are also being

developed for interior lighting. As a

result, there is growing interest in better understanding the processes that govern

the operation of metal-halide lamps.

Advances in understanding can lead to improved design rules, advanced pro- duction methods, and eventually, more

energy-efficient lighting.

I

6000

5500

5000

4500

4000

3500

3000

I

Temperature [K] Light-Emitting

Atoms [10^^ cm"^]

12

10

8

6

4

2

0

Figure 8. X-ray mapping of plasma properties in

a metal-halide lamp, a) Temperature distribution

from x-ray absorption imaging, b) Spatial distribution of atoms capable of emitting light from

x-ray induced fluorescence.

18
ATOMIC PHYSICS DIVISION

We are developing new, noninvasive

techniques to map the temperature and

the spatial distribution of atomic and

molecular constituents in metal-halide

lamps. In experiments using the

Advanced Photon Source (APS) at the

Argonne National Laboratory, one of

the world's most brilliant sources of

X rays, we have observed x-ray absorption and x-ray induced fluorescence in

operating lamps. (See Fig. 8.) The use of X rays rather than light allows investigation of advanced lamp designs having

high-temperature ceramic envelopes that

are translucent, in contrast to transparent quartz envelopes.

Some of these same techniques are now

being developed on a smaller scale at NIST using a laboratory x-ray source. This will make these new techniques more accessible to the lighting industry.

CONTACT: DR. JOHN J. CURRY

(301) 975-2817

john.curry@nist.gov

Comprehensive Atomic

Spectral Data on Xenon and

its Ions

Reliable spectroscopic data for xenon and its ions are needed in order to understand processes taking place in many different types of electrical discharges, such as those used for EUV

microlithography and the plasmas in new types of tokamaks. Although there

are numerous data for xenon in the

literature, they are scattered in a large

number of publications and can be

difficult to locate.

A critical compilation was assembled for

the energy levels, spectral lines, and ionization energies of the xenon atom and

all of its ions. This 1 57-page volume

includes 1600 energy levels and 4800

observed lines. The critical compilation

process collects the data, validates them

by using various comparisons and theoretical calculations, and provides them

in a form that is available in print as

well as on the World Wide Web.

This compilation work was complemented by an experiment that revealed,

for the first time, the detailed nature of

the spectrum of ten-times ionized xenon

at 13 nm, the region of prime interest

for EUV lithography. In this experiment, xenon gas was puffed into a high

voltage spark, and the spectrum was

observed with a high-resolution

spectrograph.

CONTACT: DR. EDWARD B. SALOMAN

(301) 975-5554

edv/ard.saloman@nist.sov

From Nanometers to

Megaparsecs: EBIT Data

Applied to Disciplines

Spanning 30 Orders of

Magnitude

With the recent addition of new measurement capabilities, the EBIT facility

is attracting a wide range of customers

who need atomic data from HCIs. At

one extreme are the astrophysicists who

are trying to resolve puzzles associated

with observed line ratios in neon-like Fe

(Fe XVII). X-ray lines from this ion are among the strongest to appear in many

spectra from space observatories such as Chandra and XMM, but their utility as

remote diagnostics is being hampered

by inconsistencies across data sets.

Figure 9. EUV spectra of xenon, taken on the

NIST EBIT. The variation of spectral features as a

function of the electron beam energy provides

valuable data for benchmarking models of the

atomic processes.

Benchmark Fe XVII data from our EBIT, previously reported in an

Astrophysical Journal Letter, has been

referenced several dozen times and has

stimulated a number of independent

experimental and theoretical studies

elsewhere. In the meantime, we have

installed a new x-ray microcalorimeter,

currently the best in the world by several measures, to address new issues raised

by the recent theoretical work.

In a very different application, Intel and

International SEMATECH have asked

us to provide benchmark data on tentimes ionized xenon, the initial ion of

choice for EUV lithography radiation

sources. (See Fig. 9.) This work was

stimulated by the needs of plasma modelers who are being employed by the

semiconductor industry to ascertain

fundamental limits on output power

and to help achieve them. In connection

with this work, the leader of the Plasma

Radiation Group was appointed Chair

of the International SEMATECH

Fundamental Data Working Group and

co-chair (with Intel) of the EUV

Source Modeling Workshop.

CONTACT; DR. JOHN D. GILLASPY

(301) 975-3236

john.gillaspy@nist.8ov

19
TO PROVIDE THE

FOUNDATION FOR OPTICAL

RADIATION MEASUREMENTS

FOR OUR NATION

OPTICAL TECHNOLOGY DIVISION

The strategy for meeting this goal is to develop andprovide national measure- ment standards and services to advance optical technologies spanning the

microwave through the infrared, visible, and ultraviolet spectral regions.

^^^e first strategic

element is to develop and

provide optical radiation

standards based on the

SI units.

Optical Radiation

Standards

INTENDED OUTCOME AND

BACKGROUND

The Optical Technology Division

plays a fundamental role in advancing

the use of optical technology. Through

research and development, we advance

the measurement science needed to maintain the Nation's primary SI standards for the candela and kelvin, and

associated photometric, colorimetric,

pyrometric, and spectral radiometric

quantities. These standards affect a

host of industries, from aerospace to

lighting, by ensuring

the accuracy and agreement of

measurements between and within

organizations.

A significant part of the Division's

activities includes participating in international comparisons of measurements

with other national metrology institutes. They are organized through the Consultative Committees on Temperature

and on Photometry and Radiometry,

of the International Committee of

Weights and Measures. These comparisons provide an important assessment of measurement quality, and help

guarantee the international acceptability

of our Nation's optical radiation

measurements.

To ensure unsurpassed measurement

accuracy, the Division's radiometric

scales are increasingly being based on

stable, low-noise, highly linear detectors,

radiometers, and photometers. Their

absolute responsivities are traceable to

optical power measurements performed

using cryogenic radiometry and a stateof-the-art laser facility, SIRCUS

(Spectral Irradiance and Radiance

Calibrations with Uniform Sources).

Cryogenic radiometry provides the

highest accuracy optical power measurements by performing a direct comparison of optical and electrical power. The

Division's High-Accuracy Cryogenic

Radiometer (HACR), the Nation's

standard for optical power, achieves a

relative standard uncertainty of better than 0.02 %.

The improvements realized by tying the

radiometric measurements to cryogenic

radiometry are significant. Recently the

Division's spectral irradiance scale, as

disseminated by FEL-type lamps, was

converted to a detector-based scale

traceable to the HACR. The improved

scale has led to a reduction of spectral

irradiance uncertainties by a factor of

two in the ultraviolet and visible, and

greater in the infrared. The spectral

radiance and radiance temperature

scales will also be detector based in

the near foture.

These advances in detector-based

radiometry are complemented by new

research in source-based radiometry, i.e., radiometry based on a source of radiation whose spectral output is absolutely

known. This research uses synchrotron

radiation from an electron storage ring.

20
the recently upgraded NIST

Synchrotron Ultraviolet Radiation

Facility (SURF III), as a source of continuously tunable, intense, ultraviolet

light. The SURF III efifort is complemented by programs to develop

improved blackbody sources.

ACCOMPLISHMENTS

High-Temperature

Radiometric Standards

To address the lack of high-temperature

standards in the International Temperature Scale of 1990 (ITS-90), the

Division is researching the suitability of

blackbody-based standards tied to the

fixed points of the phase transitions in

metal-carbon and metal-carbide-carbon

eutectics. Such fixed points offer the

potential for temperature standards as

high as 3034 K (using the TiC-C eutectic), over a factor of two greater than

the present high-temperature limit of

1358 K (fixed at the Cu freezing point).

The availability of high-temperature

standards would allow routine measure- ments to be made between 1358 K and

3034 K by interpolation rather than

extrapolation from the 1358 K standard,

resulting in a reduction of temperature

measurement uncertainties by a factor of five near 3000 K.

To accurately measure the thermodynamic temperatures of these fixed

points, the Division is developing

absolute pyrometers calibrated against

a cryogenic radiometer using SIRCUS.

The first generation of these absolute

pyrometers, denoted AP 1 and operating

at 650 nm, has a noise figure of approximately 2 mK and a one-year stability

of approximately 100 mK at 1300 K.

Efforts are directed at improving the

stability and extending the operating

wavelength into the ultraviolet near 365 nm, to achieve reduced uncertainties near 3000 K.

In assessing the appropriateness of

these eutectics for high-temperature

standards, the Division recently participated in a measurement comparison

with the National Physical Laboratory

(UK). The measured phase-transition

temperatures were compared for five metal-carbon eutectics (Co-C, 1597 K; Pd-C, 1765 K; Pt-C, 2011 K; Ru-C,

2226 K; and Re-C, 2748 K) relative to

the ITS-90 temperature scale. The

measured temperatures agreed to within

0.5 K, demonstrating the utility of these

eutectics for international temperature

standards.

CONTACT: DR. HOWARD W. YOON

(301) 975-2482

howard.yoon@nist.30v

New Infrared Calibration

Facility

The increased need for highly accurate

infrared radiation measurements for homeland security, national defense, and

remote sensing applications has led the

Division to develop, with support from

the Air Force through the Department

of Defense Calibration Coordination

Group (CCG), an infrared SIRCUS

facility.

When completed, IR-SIRCUS will

extend the visible-to-ultraviolet capabilities of the present SIRCUS into the

1 pm to 20 pm wavelength region of

the infrared, including the critical long- wave and mid-wave infrared atmospheric windows, coincident with the peak

spectral responsivities of HgCdTe and

InSb single-element detectors and focal

plane arrays. (See, e.g., Fig. 1.)

4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 — Wavelength [|jm]

Figure 1 . Spectral irradiance responsivity for an

InSb radiometer measured on IR-SIRCUS.

The facility will allow the characterization and calibration of a variety of

infrared imaging and camera systems,

including hyperspectral imagers, at a

level of detail and accuracy not possible

with conventional broadband, blackbody radiation sources.

Challenging the development of IR- SIRCUS is the lack of availability of

commercial high-dynamic-range transfer

detectors and broadly and continuously

tunable high-power infrared lasers.

Therefore, the IR-SIRCUS team has

constructed a 1 pm to 5 pm infrared

laser system based on optical parametric

oscillators (LiBjOj (LBO-OPO) or periodically poled LiNbOj (PPLN-OPO))

pumped by a mode-locked Nd:Vanadate

laser. For a transfer-standard detector

the team is using a NIST-developed,

liquid-helium cooled, electricalsubstitution bolometer.

With this laser system and detector,

infrared detectors, radiometers, and

focal plane arrays can be calibrated on IR-SIRCUS for spectral power, spectral

irradiance, or spectral radiance responsivity between 1 pm and 5 pm with a

relative standard uncertainty of 1.5 %.

CONTACT: DR. GEORGE P. EPPELDAUER

(301) 975-2338

3eorse.eppeldauer@nist.30v

21
OPTICAL TECHNOLOGY DIVISION

Novel LED Sources for

Radiometry

The Division is developing new radiometric applications for light emitting

diodes (LEDs) to take advantage of their

unique properties, which include narrow

bandwidth, high spectral brightness,

compact size, high efficiency, and

low cost.

A prototype LED-illuminated integrating sphere source has been successfully

developed using 40 LEDs operating in

10 distinct bands between 380 nm and

780 nm. Varying the light intensity in

the individual bands allows variation

of the spectral output or color, as shown

in Fig. 2. A second-generation LED

source, now under development, will

use 150 diodes grouped into 40

distinct bands to achieve a source that can match a conventional source

within 2 % for luminance and 0.002

in chromaticity.

A compact 660 nm LED source, consisting of a tube containing 36 diodes

illuminating a volume-diffuser output

coupler, has also been developed to

allow the routine monitoring of the sizeof-source error in optical pyrometers.

The size-of-source error provides a rapid

assessment of the stability of the optical

alignment of the pyrometer and the surface cleanliness of the optics. It can be an important correction to the measure- ment and an important component of

the measurement uncertainty, depending upon its magnitude.

Following a similar design, a compact,

blue LED source has been developed to model ocean color for the calibration of

instruments measuring ocean optical

properties. By matching the spectral

Figure 2. Solid-state Integrating sphere

source pumped by light emitting diodes,

showing some of the different colors that

can be generated by var/Ing the Input

current to the individual LEDs.

output to the ocean waters of interest,

many potential sources of calibration

error in the instrument under test, such

as stray light, can be reduced or eliminated.

CONTACT; DR. STEVEN W. BROWN

(301) 975-5167

steven.brown@nist.gov

^^^e second strategic

element is to develop

novel optical measurement

methods for solvins problems

in critical and emerging

technology areas.

Optical Measurement

Methods

INTENDED OUTCOME AND

BACKGROUND

The Division strives to improve the

accuracy, acceptability, and utility of

optical measurements by conducting

long-term, directed research in the

NIST strategic focus areas of homeland

security, nanotechnology, and health

care, and in such promising technology

growth areas as interface science, biophysics, semiconductor manufacturing,

and quantum communication.

In the areas of nanotechnology and

interface science, we are developing linear and nonlinear laser and near-field

techniques to characterize thin films,

surfaces, and interfaces important in molecular biology, polymer science,

and nanotechnology.

In biophysics and health care, new optical methods based on surface-enhanced

Raman spectroscopy and confocal, fluorescent imaging microscopy are being

developed to investigate single biological

molecules. This is part of a larger, interlaboratory competence program in

Single-Molecule Measurement and

Manipulation, funded by the

NIST Director.

The Division's activities in support of

semiconductor manufacturing include

research to improve the accuracy of temperature measurements during processing, through better knowledge of the

spectral emissivity of coated silicon

wafers; to advance laser optical-scattering metrology, for next-generation wafer

inspection tools; and to revolutionize

optical microscopy for quality control in semiconductor manufacturing, by using

interferometry to improve the spatial

resolution, increase the throughput, and

reduce the cost. Ultraviolet radiation

metrology is being developed to ensure

a measurement infrastructure for

1 57 nm and shorter wavelength lithography, leveraging the unique ultraviolet

radiometry capabilities of SURF III to

22
OPTICAL TECHNOLOGY DIVISION

target needs in optical-materials

properties and detector radiationdamage characterization.

In response to national priorities, the

Division continues to research optical

radiation measurements for homeland

security and national defense. Optical

measurements and standards are being

developed for missile defense, sensor calibration, target identification, and night

vision. The Division has built specialized laboratories, such as the LowBackground Infrared (LBIR) Facility

and IR-SIRCUS, to help support these

efforts. Building upon expertise developed through the NIST Directors

competence program in THz Metrology,

the Division is investigating continuous wave and femtosecond-pulsed THz

spectroscopy and imaging for the detection of chemical and biological warfare

agents. The Division is also using its unique expertise in correlated photon

radiometry to develop novel singlephoton-on-demand sources for secure quantum cryptography, in collaboration

with other Divisions.

ACCOMPLISHMENTS

Aperture Area Determinations

for Satellite Measurements

The Division is providing measurements

of the areas of precision optical apertures to improve the accuracy of satellite exoatmospheric solar-irradiance

measurements, critical for assessing the

absolute magnitude of the approximately 1 366 W/m^ solar radiation driving

Earth's weather and climate. Presently,

independent satellite exoatmospheric

solar-irradiance measurements suffer from systematic discrepancies of approximately 0.6 % over the last two decades.

reduced to 0. 1 % for the last decade.

The relative uncertainty of the aperture

area measurement places a lower limit on the relative uncertainty of the

irradiance scale.

It is anticipated that the recent launch

of the solar Radiation and Climate

Experiment (SORCE), in January 2004,

will improve solar irradiance measure- ments through better instrumentation

and increased efforts to establish traceability of the measurements to national

scales maintained by NIST. For the

Total Irradiance Monitor and the

Spectral Irradiance Monitor aboard the

SORCE satellite, NIST has provided

accurate measurements of the areas of

the apertures for the irradiance

measurements, and has modeled the

diffraction corrections associated with

transmission through the apertures.

The NIST measurements were per- formed at the Aperture Area Measurement Facility. The facility uses a coordinate measuring machine to ascertain

selected edge points of the aperture, as

located by a video microscope. Distances are measured interferometrically,

yielding aperture areas with typical relative standard uncertainties {k = 1) of

approximately 2.5 x 10~^

The Division is also leading a comparison of aperture area measurements

among laboratories involved in the

development of exoatmospheric solarirradiance sensors. Its main goal is to

assess whether inaccurate aperture area

determinations are the origin of the discrepancy in reported solar irradiances.

The comparison, which so far includes

two other laboratories, indicates that

aperture area measurements account for

<0. 1 % of observed variation among

sensors.

CONTACT; DR. AAARITONI LITORJA

(301) 975-8095

maritoni.litorja@nist.gov

Workshop on Satellite

Instrument Calibration

In January 2004, the Division released

its final report from the workshop.

Satellite Instrument Calibration for Measuring Global Climate Change,

held in November 2002 and jointly

organized by NIST through the Optical

Technology Division, the National

Polar-orbiting Operational Environmental Satellite System-Integrated

Program Office, NOAA, and NASA.

This workshop was initiated to address

the measurement challenges and instrument calibration needs for the accurate

space-based measurement of global cli- mate-change variables such as atmospheric temperature and solar irradiance.

These variables are critical for assessing

the magnitude of, and determining an

effective policy response to, global

climate change.

The NIST report, NISTIR 7047, summarizes the required absolute accuracies

and stabilities of climate-change variable

determinations for use in predictive cli- mate-change models. The report relates

required climate-change variable accuracies and stabilities to satellite measure- ment accuracies and stabilities. The

report also assesses the ability of present

satellite technology to deliver the

required measurement accuracy and stability. Guiding principles to maintain

and improve the accuracy of satellite

23
OPTICAL TECHNOLOGY DIVISION

Figure 3. Vacuum goniometer

for the measurement of the

spectral emittance of specular samples as a function of

temperature and angle.

remote-sensing measurements, through

better instrument calibration and validation, are also provided in the report.

Finally, the report ends with a proposal

for a follow-up workshop to develop an implementation plan for the recommendations. Such a follow-up workshop is planned in the near future.

CONTACT: DR. RAJU V. DATLA

(301) 975-2131

raju.datla@nist.gov

Emittance Measurements for

Semiconductor Manufacturing

A new facility has been developed to determine the emittance of silicon

wafers as a fiinction of temperature,

wavelength, and angle, in order to improve temperature measurements during semiconductor manufacturing. The

emittance of a material means how well

it emits optical radiation relative to an

ideal, blackbody radiator. Knowledge of

the emittance of a material is essential

for accurate noncontact temperature

measurements based on Planck's Radiation Law. Such measurements are per- formed in support of many industrial

processes, including the fabrication of

metals, glasses, and complex semiconductor wafers.

The new facility (Fig. 3) uses reflectance and transmittance measurements

between 600 nm and 3 \im, soon to be

extended to 10 |im, to derive the sample

emittance. The radiation is provided by

a lamp source dispersed by a double

monochromator. Detectors mounted on

a rotation stage allow the measurement

of the angle-dependent emittance. The

system is designed for both opaque and

semitransparent materials with specular

(mirror-like) surfaces, such as polished

silicon wafers. The sample temperature

is variable from below ambient to 1200 K. Measurements are made under

a vacuum or in a purged gas environment to limit sample oxidation at the

higher temperatures.

CONTACT: DR. LEONARD M. HANSSEN

(301) 975-2344

leonard.hanssen@nist.sov

Improved Ocean-Color

Measurements

To improve satellite ocean-color

measurements used to estimate ocean- carbon levels. Division scientists have

undertaken a detailed optical characterization of the Marine Optical Buoy

(MOBY), permanently stationed off the

coast of Hawaii. MOBY uses dual imaging spectrographs to provide measure- ments of ocean-leaving radiances and

downwelling radiances. These data are compared to simultaneous measure- ments performed by overflying satellites such as the Sea-viewing Wide Field-ofview Sensor (SeaWiFS) and the

Moderate Resolution Imaging Spectroradiometer (MODIS), thus providing

vicarious calibration of the satellite measurements.

The motivations for the characterization were the discrepancy between MOBY's

two spectrographs (denoted red and

blue) in their overlap region and the

unphysical, negative leaving radiance

observed at short, near-ultraviolet wavelengths in the blue channel. To undertake the characterization. Division scientists developed Traveling SIRCUS for

the off-site characterization of the spectral responsivity of the instrument, using

a tunable-laser-illuminated integratingsphere source.

The measurements demonstrated that

stray light within the spectrographs from

high-order grating reflections and scattered light caused the problems. A correction algorithm was developed that

removed the spectral artifacts caused by

the stray light. The corrections due to

stray light alone have led to a lowering

of the SeaWiFS satellite measurements

of global chlorophyll a concentrations,

and associated ocean-carbon levels, by

24
OPTICAL TECHNOLOGY DIVISION

approximately 15 % to 20 %. When

combined with other readjustments, the

values were approximately 6 % lower

than those previously accepted.

CONTACT: DR. CAROL JOHNSON

(301) 975-2322

cjohnson@nist.gov

Coherent Control Explored In the Condensed Phase

The Division, in collaboration with

the Max Planck Institute in Garching,

Germany, has investigated the molecular

response following amplitude- and

phase-controlled femtosecond midinfrared multiphoton excitation of a

molecular stretching vibration. In this

case, the carbonyl stretch in tungsten

hexacarbonyl, WCCO)^, was studied.

Such coherent-control methods offer

the potential of directly controlling

intermolecular and intramolecular

energy-transfer processes and chemical

reactions, through the optimal

preparation of vibrationally excited

precursor molecules.

W(CO)6 in hexane solution was selected

as a test case because its CO-stretching

ftindamental has both a large transition

dipole moment, necessary for a high

quantum yield, and a large vibrational

anharmonicity, allowing resolution of

individual v + I <r- v vibrational hotband transitions. In addition to measuring the anharmonic shifts and

linewidths of the v + I <r- v progressions, controlled population distributions were compared to Bloch model

calculations for the excitation process.

The main result, presented in Fig. 4,

shows differential absorption for vibrationally excited W(CO)6 in room temperature ra-hexane as a function of probe

frequency. A strong ground-state bleach

D -0.05 O

<1 -0.10

-0.25

1966 cm'

1951 cm''

. 1930cm'',„„, ., /\. ^. 19°Z£'^ 1882 cmPump energy = 8.5 |jJ At = 1 ps

2000 1980 1960 1940 1920 1900 1880

Wavenumber [cm"'']

Figure 4. Spectrum showing differential

absorption for vibrationally excited W(CO)5 in

room-temperature n-hexane as a function of

probe frequency. A strong ground-state

bleach signal at 1980 cm"'' is accompanied

by five new absorption bands, from the first

five \/+ 1 <— v hotband transitions.

signal at 1980 cm~' is accompanied

by five new probe absorption bands

from the first five Av=\ hotband transitions. Probe absorption at 1882 cm^',

arising from the = 6 <— 5 transition,

implies population transfer to y = 6,

corresponding to an energy of nearly

12,000 cm"^ deposited into a single

vibrational mode. About 0.5 % of the

molecules are excited to the dissociation

energy limit for a W-C bond.

Future experiments will attempt to

induce ground-electronic-state molecular bond dissociation in the condensed

phase. Planned extensions of this study

include applying feedback to the amplitude and phase modulated MIR laser

pulses to increase the energy deposited

into the vibrational mode.

CONTACT; DR. EDWIN J. HEILWEIL

(301) 975-2370

edv/in.heilv/eil@nist.gov

Terahertz Spectroscopy of

Polypeptides

The continuous wave terahertz spectra

of small polypeptides have been measured to better understand the lowfrequency, large-amplitude vibrations

responsible for the flexibility of

biological molecules.

Tunable THz radiation was generated

by the solid-state photomixing of two

near-infrared laser beams separated in

frequency from 0.1 THz to 3 THz.

Samples of a polypeptide mixed in a

transparent polytetrafluoroethylene

matrix or dissolved in an aqueous solution were studied from 4.2 K to 300 K.

Spectra were recorded for the series of

polypeptides from alanine to hexa-alanine, in different crystalline forms.

Variations in the spectra with crystal

structure, hydration level, and

temperature reveal the importance of

intermolecular hydrogen bonding and

vibrational anharmonicity in controlling

the dynamics of the low-frequency

vibrational modes. The positions of the

absorption peaks change dramatically

with water hydration level due to perturbations of the vibrational force field from hydrogen bonds between the peptide and neighboring water molecules in

the matrix. A decrease in the apparent

vibrational anharmonicity with decreasing temperature leads to a narrowing of

the absorption peaks and a decrease in

the asymmetry of the lines' profiles.

Efforts at modeling these effects are underway, to allow the extraction of

quantitative information about the

inter- and intramolecular force fields of these model polypeptides.

CONTACT: DR. DAVID F. PLUSQUELLIC

(301 ) 975-3896

david.plusquellic@nist.gov

25
OPTICAL TECHNOLOGY DIVISION

he third strategic

element is to disseminate

optical radiation measurements and standards to

industry, sovernment,

and academia.

Optical Measurement

Services

INTENDED OUTCOME AND

BACKGROUND

The Division builds and maintains

world-class optical radiation measure- ment 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 refer- ence materials available from NIST

Technology Services, or through collaborative researchefifcorts.

The Division maintains facilities for measuring optical properties such as

reflectance, retroreflectance, transmittance, color, and gloss; for photometric

measurements such as luminous intensity and color temperature; and for radiometric measurements such as spectral

radiance, spectral irradiance, spectral

power, detector responsivity, and radi- ance 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 are under development to measure the emittance of

materials and to provide standards for

ultraviolet spectral irradiance.

The Division strives to ensure the

quality of these programs by publishing our research and measurement methodologies as NIST Special Publications or

in outside peer-reviewed archival journals; by participating in measurement

comparisons with other laboratories;

and by maintaining a measurement

quality program. The Division also aids

the dissemination of good optical-radiation measurement practice by publishing training documents and by offering

formal short-courses in photometry,

spectroradiometry, and radiation temperature measurement. We are enlarging

this activity to provide training at cus- tomer sites when the demand is large

and resources are available.

ACCOMPLISHMENTS

New LED Measurement

Services Launched

The Division's conventional measure- ment services for the lighting industry

have been optimized for standard incandescent and fluorescent lighting, and

thus do not encompass the unique spatial and spectral distributions of LEDs.

However, the Division has developed

several new measurement services for LEDs, providing critical standards

necessary for our Nation to rapidly

realize the significant energy and cost

savings, and greenhouse-gas reductions,

expected for solid-state lighting—and

to become a commercial leader in this new technology.

New measurements services include the

calibration of photometric quantities

such as averaged LED luminous intensity in candelas and total luminous flux in lumens, and of colorimetric quantities

such as chromaticity coordinates and

dominant wavelength. (See Fig. 5.) Uncertainties {k = 2) of 1 % to 3 % for

averaged LED luminous intensity, 1 %

to 2 % for luminous flux, and 0.001 in

(x, y) chromaticity coordinates have

been achieved.

These measurement services are necessary tools for industry to assess the

performance of LEDs and to ensure

consistent measurements between manufacturers. The colorimetric standards

will also help industry to optimally

blend combinations of LEDs to achieve

the color rendering demanded by users.

Future efforts will include developing

approaches for the radiometric calibration of LEDs in the ultraviolet and

near-infrared spectral regions.

CONTACT: MR. YUQIN ZONG

(301) 975-2332

yuqin.zong@nist.30v

Fisure 5. Yuqin Zons alisns a sreen LED for

caribration on the reference spectroradiometer

26
OPTICAL TECHNOLOGY DIVISION

Center for High-Accuracy

Retroreflection

Measurements (CHARM)

The Division has recently completed

development of a new facility to measure the retroreflectivity of pavement

markings and road signs, with financial

support from the National Cooperative

Highway Research Program. The facility was developed in response to a Congressional directive to the U.S. Department of Transportation to establish "a

standard for a minimum level of retroreflectivity that must be maintained for pavement markings and signs which

apply to all roads open to public travel."

The requirements for the NIST reference retroreflectometer were based on a

careful examination of national and

international documentary and artifact

standards, and discussions with experts.

The facility is installed in a 40 m long

tunnel, and consists of a six-axis goniophotometer, a uniform beam source, and a detector system mounted on

35 m long rails. (See Fig. 6.)

Fisure 6. Cameron Miller mounts a STOP sisn on the soniometer at the NIST Center for

Hish-Accuracy Retroreflection Measurements

(CHARM).

The instrument has been fully characterized, and a complete uncertainty

analysis has been performed. A calibration of typical retroreflective sheeting

material for coefficient of luminous

intensity will yield a relative expanded

uncertainty of 1 % = 2). Typical

pavement marking materials will have a

slightly higher relative expanded uncertainty of approximately 2 % (k = 2). An official calibration service for

retroreflectance materials began

in 2004.

CONTACT: DR. CAMERON MILLER

(301) 975-4713

c.miller@nist.sov

LBIR Facility Aids Missile

Defense

Recent upgrades in the LBIR Facility

have improved the Division's ability to

provide infrared measurements and

standards critical to the development

and implementation of the U.S.

National Missile Defense (NMD)

system. This work supports the mission

of the Ballistic Missile Defense

Organization (BMDO) by helping to

ensure that the infrared sensors mounted on interceptor missiles can reliably

discriminate between target and decoy.

The LBIR Facility uses specialized

radiometric test chambers and radiometers to disseminate the NIST infrared

radiance scale to Government and contractor sites, by providing on-site calibration of blackbodies or off-site calibration of test chambers. Upgrades to

the LBIR Facility included improvements in the cryogenic system to allow

operation down to 1 5 K (the previous

system limit was 25 K), and the addition of a low-noise absolute cryogenic

radiometer. Together these improvements have led to a factor-of-ten reduction in the measurement uncertainty for

on-site blackbody calibrations.

Improvements have also been made in

the ability to provide off-site calibration

of cryogenic test chambers using the

2 pm to 30 pm BMDO Transfer

Radiometer (BXR I). The BXR I has

been sent to space test chambers at

Boeing, Raytheon, and the Air Force to

tie measurements performed at these

sites to the NIST High-Accuracy

Cryogenic Radiometer. Improvements

in the calibration of the BXR I radiomeFigure 7. James Fedchak and Allan Smith install

the new 10 cm collimator in the LBIR Facilit/ to

reduce the uncertaint/ in the calibration of the

BXR I transfer-standard radiometer

ter at NIST are being undertaken by

using a specially designed 10 cm light

collimator to better simulate the

performance of the space chambers

calibrated in the field by the BXR I

(Fig. 7). Implementation of this

collimator in the calibration of the

BXR I at NIST is expected to provide a

three-fold improvement in the measure- ment uncertainty at the NMD space

chambers. Such improvements are

essential if infrared sensors are to meet

fliture NMD accuracy requirements.

CONTACT; DR. ADRIAAN CARTER

(301) 975-4765

adriaan.carter'@nist.gov

27
The first strategic element

is to develop and provide

standards for radioactivity

based on tine SI unit, the becquerel, for homeland security,

environmental, medical,

and radiation protection

applications.

Radioactivity

Standards

INTENDED OUTCOME AND

BACKGROUND

The Radioactivity Group is responsible

for developing metrological techniques

to standardize new radionuclides for

research, and for exploring applications

in health care, worker protection,

environmental protection, and national

defense.

mum %v A%

ADIATION DIVISIO

The strategy for meeting this goal is to develop, maintain, and disseminate

the national standards for ionizing radiation and radioactivity to meet

national needsfor health care, U.S. industry, and homeland security.

A vigorous program is underway to

develop microcalorimetric methods for measuring power from radioactive

sources. This work is proceeding in

parallel with use of liquid scintillation

detector methods based on triple-todouble-coincidence ratio (TDCR)

counting. Accurate activity measure- ments over a broad dynamic range are

obtained using these two complementary techniques. For ultralow-level atom

counting, we are continuing development of resonance ionization mass

spectrometry (RIMS), which has applications in nuclear forensics as well as

in environmental radioactivity.

The Radioactivity Group provides leadership in a national program for radiopharmaceutical standards. We provide

the national standards for nuclear medicine radionuclides used in 13 million

diagnostic procedures and 200,000

therapeutic procedures annually in the

U.S. A major effort in this area is to

provide traceability not only to the

manufacturer of the radiochemicals, but

also to the clinic. This has been realized

for the recently approved drug Zevalin,

used in the treatment of refractory

non-Hodgkin's lymphoma (Fig. 1).

Because of heightened concern in the

U.S. about possible terrorist attacks

using radiological or nuclear weapons,

we are leading a national effort to develop standards and protocols for radiation

instrumentation for first responders.

Expanding efforts are directed at four

goals: 1) validation of equipment standards and test methods for handheld

detectors for first responders; 2) a test- bed for cargo container and truck

inspections for radiological and nuclear

materials, including the coordination of

instrument testing within the National

laboratories; 3) radionuclidic forensic

Figure 1 . Calibration of '°y in a syringe

geometr/ for nuclear medicine applications.

28
methods based on mass spectrometry;

and 4) a national quality assurance

system that supports homeland security

needs.

Many tens of thousands of low-level

radiochemical measurements are made

annually to support environmental

remediation and occupational health

programs. The credibility of these measurements has been based on participation in regulation-driven performance

evaluation programs of limited scope. The metrology community recognized a fundamental flaw—that there was often

a lack of direct linkage to national

radioactivity standards. This situation

is being addressed by the publication of

three ANSI standards. These consensus

standards call for a traceability-testing

program that links the quality of

operational measurements to national

standards.

ACCOMPLISHMENTS

Testing of Radiation

Detection Portable and Portal

Instruments

Characterizations of commercially

available instruments for measurement

and identification of unknown radionuclides were carried out in support of the

development and testing of American

National Standards Institute (ANSI)

standards N42.32, N42.33, N42.34,

and N42.35. Measurements were based on the performance of the devices, i.e.,

the capability of the detectors to ensure

a correct radionuclide identification and

to determine exposure or dose-rate values, in a given time interval, for various

radioactive sources and accuracies.

Thirty portable instruments and four

portal monitors were tested. The

portable instruments' responses, as a

function of energy, were tested using

two *^^Co and two ranges, as well

as the x-ray range operating at effective

energies of 47 keV, 80 keV, and

120 keV.

For portal monitors, a new testing

facility was installed, allowing the testing

of these monitors using several radioactive sources transported through the

monitors at different speeds and distances. The monitors were field-tested in

a parking lot and at the NIST C Gate.

The availability of this new testing facility and our access to a wide variety of

radioactive sources allow us to test portal monitors presently being developed

for detection and identification of

radionuclides.

CONTACT: DR. LETICIA PIBIDA (301) 975-5538

leticia.pibida@nist.30v

Gamma-Ray Emitting Test

Sources for Portal Monitors

used for Homeland Security

Basing our research on the new

ANSI N42.35 standard, "Evaluation

and Performance of Radiation Detection

Portal Monitors for Use in Homeland

Security," as well as the related Test and

Evaluation Protocol for Homeland Security, we developed a set of test sources

for the testing of portal monitors.

(See Fig. 2.)

The standard specifies that the test

sources should be point sources (relative

to the size of the portal monitors), single

radionuclides, and encapsulated in

0.25 mm thick stainless steel disks. The

1 1 1

.€)|0|.(Qj:0

n

Fisure 2. Radioactive test sources developed at

NIST for the testins and evaluation of radiation

detectors to be used by first responders.

radionuclides required for portal monitor testing are ^^Co, "^"Co, ^^^Ba, '^^Cs,

^^^Th, and ^^'Am. These sources are

useable not only for testing and evaluating instrumentation, but also for calibrating test sources and for training

instrument users.

We are aware of five companies that

currently produce or distribute radioactive sources in the USA. AEA Technology showed an interest in commercializing our test sources, and they are getting

ready to produce and distribute them

more widely.

AEA Technology participates in a Measurement Assurance Program with

NIST to assure traceability to U.S.

national standards for sources used in

nuclear power and medical applications.

A similar and more extended program

is being implemented for homeland

security applications.

CONTACT; DR. LETICIA PIBIDA (301) 975-5538

leticia.pibida@nist.gov

29
IONIZING RADIATION DIVISION

MIcrocalorimetry for Absolute

Radioactivity Standardizations

A commercial "isothermal microcalorimeter" has been adapted for use in performing classical, calorimetric-based

calibrations of radioactive sources. Microcalorimetry is one of the best nondestructive methods for the standardization of small, high-activity (GBq-range),

P and x-ray sources, a category under

which almost all brachytherapy

sources fall.

This dual-cell, near-isothermal (heat

flow) microcalorimeter operates at near- ambient temperatures, utilizing specially

fabricated, source-holder measurement

cells that are used to maximize the energy absorption of the ionizing radiation.

It incorporates resistance heaters within

the measurement cells to very accurately

determine power calibrations.

In 2004, to improve the temperature

stability of the operating environment,

the isothermal microcalorimeter was moved into the new AML building. The

instrument is now located in a laboratory with ambient temperature stabilized

to 0.2 °C, which has increased the stability of the instrument baseline, and

thus its sensitivity, by a factor of two.

The isothermal microcalorimeter was

used for the calibration of an ^Spe lowenergy x-ray source. The low energies of

the emitted x rays and Auger electrons

(less than 6.5 keV) made use of conventional counters to measure this radionuclide extremely difficult. On the other

hand, the low energy of the decay particles allowed for the primary calibration

of ^^Fe by microcalorimetry without the

need for an additional absorber within

the cell, thus increasing sensitivity.

Preliminary results suggest that the

standardization of ^^Fe sources by

isothermal microcalorimetry can be

performed with an expected accuracy

of better than 1 %.

CONTACT: DR. PETER VOLKOVITSKY

(301) 975-5527

peter,volkovitsky@nist.sov

Measurement Standards for

Recently Approved

Radiotherapy Nuclide

The American Cancer Society estimates

that there will be 64,000 new cases of

lymphoma in the U.S. this year, with an

expected five-year survival rate (for nonHodgkin's lymphoma) of 52 %. One of

the most promising new drugs for treat- ment of this disease is Zevalin, which is

a monoclonal antibody labeled with the

radionuclide ^°Y. While ^^Y has many

properties that make it suitable for use

in radiotherapy, those same properties

present a number of challenges regarding its measurement.

FDA approval of Zevalin brought about

an exploding need for standards and

measurement quality assurance for

radiopharmaceuticals using ^''Y. A workshop held at NIST in December 2001

identified the measurement issues

involved. Invited speakers included representatives from NIH, radiopharmaceutical manufacturers, radiopharmacies,

isotope producers, government regulators, and NIST.

As a result, NIST examined the measurement of ^°Y solution standards in

clinically useful geometries, to develop

calibration factors and an estimation of

the uncertainties involved in those measurements. NIST worked with radiopharmacies, the FDA, the Society of

Nuclear Medicine, the American

Pharmaceutical Association, and others

to organize and implement a protocol to

establish measurement traceability for

the estimated 450 radiopharmacies.

In related work, NIST assisted in the

development of a long-term standard for

the calibration of detectors used in ^"^Y measurements. The short half-life

(64.053 h) of 90Y does not allow for long-term use of a single standard

source. However, AEA Technology QSA

(Burlington, Massachusetts) manufactures a mock '°Y syringe using a solid

source of the long-lived parent radionuclide ^°Sr. NIST examined the characteristics of these sources in a detector, as compared to those of ^'^Y solution

sources. With the proper execution of an initial calibration exercise at a clinic,

these standards may be used to check

calibration throughout the year.

CONTACT; MR. JEFFREY T, CESSNA

(301) 975-5539

jeffrey.cessna@nist.30v

30
IONIZING RADIATION DIVISION

T

I he second strategic

element is to develop and

provide neutron standards

and measurements needed

for fundamental physics,

homeland security, the

hydrosen economy, worker

protection, and nuclear

power.

Neutron Standards

and Measurements

INTENDED OUTCOME AND

BACKGROUND

The Neutron Interactions and

Dosimetry Group provides measure- ment services, standards, and fundamental research in support of NIST's

mission as it relates to neutron technology and neutron physics. The national

interests served include industrial

research and development, national

defense, homeland security, higher education, electric power production, and more specifically, neutron imaging,

scientific instrument calibration and

development, neutron source calibration, detection of concealed nuclear

materials, radiation protection, and

nuclear and particle physics data.

The Group maintains and disseminates

measurement standards for neutron

dosimeters, neutron survey instruments,

and neutron sources. The Group has

initiated an accelerated program to

develop effective neutron interrogation

and measurement standards for national

defense and homeland security needs,

in collaboration with the Radioactivity

Group.

The Group maintains and supports the

Nation's premier fundamental neutron

physics user facility. The Neutron

Interferometry and Optics Facility is one of the most advanced user facilities of this kind in the world. The Group's

neutron interferometry program provides the world's most accurate measure- ments of neutron coherent scattering

lengths, important to materials science

research and modeling of the nuclear

potentials. Preparations for new neutron

interferometry experiments for surface

studies of multilayers, for determination

of the charge distribution in the neutron, and for investigation of quantum

information/coherence phenomena are

being carried out.

The Group is at the forefront of basic

research with neutrons in the measure- ments of symmetries and parameters

of the weak nuclear interactions,

addressing fundamental issues that are important in the understanding of

theories of evolution of the cosmos. It is an internationally renowned program

that maintains an extensive level of

cooperation with premier national and

international academic and research

institutions.

We have developed and we maintain the

Nation's only high-resolution neutron

imaging user facility. It is available for both proprietary and open research at

the NIST Center for Neutron Research

(NCNR). Research at this facility is primarily dedicated to applying neutron

imaging methods for industrial research on water transport in fuel cells and on

hydrogen distribution in hydrogen

storage devices. Neutron imaging, vigorously pursued by the Group, has rapidly

developed to be the technique of choice

for nondestructive, in situ water transport studies in PEM-type fuel cells. This facility has provided critical

services to major automotive and fuel

cell companies, and continues to be

in high demand.

The Group is also among the world

leaders in developing -^He-based neutron

polarization and analysis techniques.

We are developing and promoting the

applications of neutron spin filters based on laser-polarized ^He. The technique

has the unique capability to polarize a polychromatic neutron beam without

introducing additional beam divergence.

This is a very attractive feature for many

materials science and fundamental

physics applications. We are pursuing

applications at the NCNR, the Intense

Pulsed Neutron Source (IPNS) at Argonne National Laboratory, and the

Los Alamos Neutron Science Center.

ACCOMPLISHMENTS

Neutron Technology for

Homeland Security

We have participated in the development of three new ANSI Standards,

N42.32, N42.34, and N42.35, which

provide test and evaluation protocols for neutron detection in personal electronic

radiation monitors ("pagers"), isotope

identifier instruments, and portal monitors, respectively. We are managing the

procurement, calibration, and dissemination of standard, low-intensity neutron sources to three national laboratories for testing of commercial instru31
IONIZING RADIATION DIVISION

merits under these standards. We are

also leading the development of new,

additional ANSI standards on neutron

survey meters and active interrogation

devices for detection of fissile material,

explosives, and chemical agents.

The challenge of calibrating low-intensity sources has motivated the development of a new source comparator with a reduced-volume manganese sulfate bath.

For measurement of neutron radiation

protection levels around active interrogation devices, we have procured and

calibrated state-of-the-art commercial

neutron spectrometry and absorbeddose measurement systems.

We are developing neutron spectrometers and epithermal/thermal neutron

detectors with much higher sensitivity

than current state-of-the-art systems.

We are experimenting with muon anticoincidence techniques for reducing the

cosmic-ray component of neutron

background radiation. Finally, we have

procured and calibrated a small, sealedtube source for generating 14 MeV and

2.5 MeV fast neutrons, for testing our new spectroscopy systems, and for

developing radiation-protection

dosimetry capabilities up to 14 MeV.

CONTACT: DR. DAVID M. GILLIAM

(301 ) 975-6206

david.gilliam@nist.gov

New Imaging Station for

Fuel Cell Research

The Neutron Imaging Facility started

flill-time operation in 2003 at Beam

Tube 6 (BT-6) at the NCNR. The facility has an extremely high fluence rate of

1.8 X 10^ cm~^ s"^ uniformly spread

over a 26 cm diameter area, with an L/d

ratio of 300, which is needed to achieve

optimum geometric sharpness of the

image. This is one of the most advanced

neutron imaging facilities in the world

and the best of its kind in the U.S.

We have pioneered nondestructive

imaging techniques to map critically

important hydrogen and water motion

in operating fuel cells. This facility has

been hosting experiments from industrial fuel cell developers, interested in looking at the distribution of water in operational fiael cell systems using standard

fuel cell hardware. First-generation neutron experiments with a major industrial

partner show exciting promise of

robust/efficient fuel cell design, substantial reduction in fuel cell development

time, and establishment of uniform

characterization/performance standards

This program has been awarded NIST

competence research funding and, in 2003, DOE recognized this program as one of the top-ten programs relevant to

the "FreedomCAR" program initiated

by the President.

CONTACT: DR. DAVID L. JACOBSON

(301) 975-6207

david.jacobson@nist.gov

Fisure 3. Pieter Mumm

(second from right) and

colleagues setting up a

neutron decay detector

for the time reversal

asymmetry experiment

(emiT).

Neutron Measurements to

Test "Standard Model"

The emiT experiment successfiilly

completed its data acquisition on NG-6 in December 2003. (See Fig. 3.) The experiment is a collaboration

among NIST, the University of

Washington, the University of

California (Berkeley), the University

of Michigan, Hamilton College,

and Tulane University.

The experiment searches for (or will set an improved upper bound on) the timereversal asymmetry term in neutron beta

decay. It does so by measuring electronproton coincidence events from the

decay of polarized neutrons. An asymmetry in coincidence pairs is formed as

a function of the direction of the neutron spin. A measurement of a nonzero asymmetry would be an indication of

time-reversal violation.

The measured electron-proton coincidence rate is a factor-of-ten higher than

in the first run. In addition, the signalto-background ratio is two orders of

magnitude higher. The analysis of the

data is in progress, and we anticipate a

result that is approximately a factor of

four better than the world current limit.

Work has commenced at NG-6 on an

effort to measure the radiative decay

mode of the free neutron. The usual

beta decay of the neutron into a proton.

32
IONIZING RADIATION DIVISION

electron, and antineutrino is occasionally accompanied by the emission of a

photon. Despite decades of detailed

experimental studies of neutron beta

decay, this branch of a fundamental

weak decay has never been observed.

Our technique is based on measuring

the triple coincidence of the proton and

electron along with the rare photon.

The experiment should not only

definitively see radiative neutron beta

decay for the first time, but also per- form a 5 % measurement of the

photon spectrum.

CONTACT: DR. JEFFREY S. NICO

(301) 975-4663

jeffrey.nico@nist.sov

Polarized ^Hc Neutron Spin

Filters for Fundamental and

Applied Research

In collaboration with scientists in the

NIST Materials Science and

Engineering Laboratory and Indiana

University, we are employing ^He-based

polarization analysis for dififiise reflec- tometry at the new Advanced Neutron

Dififractometer/Reflectometer at the

NCNR, and the POSY-I reflectometer

at IPNS.

Our current focus is on studies of

patterned magnetic materials, which are

relevant to the development of future

magnetic storage media (Fig. 4). In

addition, we are collaborating with

researchers from Hamilton College,

IPNS, and the Spallation Neutron

Source in the application of a continuously operating ^He polarizer for

single-crystal dififractometry.

0.0001 0.001

Reflectivity

0.01 0.1 T

E

cO

O

1.00 0.10 0.20 0.30 0.40 0.50 [nm-!]

Figure 4. Polarization analysis of neutron reflection from a sample of cobalt "antidots,"

obtained with a -^He analyzer and a positionsensitive detector and are the z and x

components of the wavevector transfer; spin-flip

scattering from magnetic domains is evident in

the off-specular data.

In fundamental physics, we are contributing to the operation and further

development of the ^He polarizer for an

experiment in weak interaction physics

(the "npdy experiment) at Los Alamos

National Laboratory. In addition, we are

developing ^He cells for a planned

measurement of the spin dependence of

the ^He scattering length on the NCNR

neutron interferometer. In collaboration

with the University of Utah, we have

documented remarkable magnetic

effects in the polarized ^He storage cells, which are relevant to suppressing wall

relaxation time.

CONTACT: DR. THOMAS R. GENTILE

(301) 975-5431

thomas.gentile@nist.sov

he third strategic

element is to develop dosimetric standards for x rays,

Samma rays, and electrons

based on the SI unit, tlie sray,

for homeland security, medical, radiation processins,

and radiation protection

applications.

Radiation Dosimetry

Standards

INTENDED OUTCOME AND

BACKGROUND

The Radiation Interactions and

Dosimetry Group promotes the accurate and meaningful measurements of dosimetric quantities pertaining to ionizing

radiation: x rays, gamma rays, electrons,

and energetic, positively charged particles. We maintain the national measure- ment standards for the Systeme

International (SI) unit for radiation

dosimetry, the gray.

NIST is a world leader in the measure- ment of high levels of absorbed dose, as

required in the industrial radiation processing of materials (e.g., sterilization of single-use medical devices, food irradiation, and destruction of biological

weapons). Accurate transfer dosimetry

is increasingly done on the basis of

alanine/EPR (Electron Paramagnetic

Resonance) dosimetry, rather than

radiochromic film dosimetry, which was

originally developed at NIST and

offered for many years as a calibration

service. A new NIST system is near

33
IONIZING RADIATION DIVISION

completion for on-demand, Internetbased ^-calibrations for industry, based on alanine/EPR dosimetry.

Brachytherapy (treatment with sealed

radioactive sources) has seen a tremendous increase in the use of low-energy,

photon-emitting seeds to treat prostate

cancer and in the use of beta-particle-

(and photon-) emitting sources to inhibit arterial restenosis (re-closing) following balloon angioplasty. In both cases, NIST has responded to the needs of the

manufacturers, regulators, and clinical

physicists. We develop new standards

and measurement methods to calibrate

the quantities needed to ensure accurate dosimetry for the wide variety of sources

introduced, and we disseminate these

standards through a network of secondary calibration laboratories.

Nearly 700,000 cancer patients per year

are treated in the U.S. with radiation

beams, mainly from high-energy electron accelerators (either directly with

the electrons or by converting them to

high-energy x rays). NIST maintains

and disseminates the standards for air kerma (exposure) and for absorbed dose

to water from ^^Co gamma-ray beams.

These provide the basis for calibrating

instruments used to measure the

absorbed dose delivered in therapy

beams.

Standards for diagnostic radiology are developed and maintained at NIST in

terms of air kerma, for x-ray beams from

10 kV to 300 kV (x-ray source accelerating potential in kilovolts). These are dis- seminated to manufacturers and the

medical physics community in North

America through a network of secondary calibration laboratories. NIST maintains some 85 beam qualities for conventional, W-anode, x-ray beams, and

17 beam qualities for mammographic,

Mo- and Rh-anode, x-ray beams.

The radiation transport and Monte

Carlo methods pioneered and developed

at NIST to calculate the penetration of

electrons and photons in matter are used in most of the major codes today.

Monte Carlo simulation is increasingly

applied to problems in radiation metrology, protection, therapy, and processing

as an accurate tool for designing and

optimizing radiation systems and for

providing important insight into

processes inaccessible to measurement.

ACCOMPLISHMENTS

Assistance to U.S. Postal

Service in Decontamination

of Mail

After anthrax-laced mail was delivered

to media and government offices, resulting in five deaths, numerous illnesses,

and enormous disruption and economic

loss, we responded rapidly to identify

industrial irradiation of the mail as an

effective and readily available process to

kill anthrax spores. Leading a task force

established by the White House Office

of Science and Technology Policy, we

worked with the Armed Forces Radiobiology Research Institute, the

U.S. Postal Service (USPS), and industrial irradiation facilities to provide

critical dosimetry measurements and

to validate the process.

Based on an extensive program of

Monte Carlo radiation transport calculations and accurate dosimetry measurements in a variety of mail configurations, NIST provided advice for optimizing the process parameters and

developing a national strategy to

effectively handle the highly variable

mail and parcel stream.

This collaboration continues, expanded

to include qualitative measurements of

radiolytic products produced in the mail

during the irradiation, quantitative

measurements of the effects on the

archival properties of paper due to irradiation, and the design of a dedicated

USPS mail-irradiation facility.

CONTACT: MR, STEPHEN M. SELTZER

(301) 975-5552

stephen .se Itze r@n ist. gov

High-Energy Computed

Tomography Facility

The 7 MeV to 32 MeV Saggataire

electron linac in the NIST Medical

Industrial Radiation Facility (MIRF)

offers unique possibilities as an x-ray

source for a high-energy computed

tomography (HECT) facility. A beamline and camera are under development

at MIRF to study the x-ray inspection

of cargo containers, trucks, and other

large objects.

We are also carrying out theoretical

and experimental investigations into

neutron production in high-energy x-ray

beams. It might prove possible to also

use photoneutrons, produced at high

photon energies, as an active probe to

interrogate containers and screen for

explosives and other terrorist materials.

CONTACT: MR. JULIAN H. SPARROW

(301) 975-5578

julian.sparrow@nist.gov

34
IONIZING RADIATION DIVISION

Radiation Sources for Medical

and Industrial Applications

In addition to a dozen gamma-ray

(^"Co and ^^^Cs) sources and five x-ray

ranges, we maintain MIRF, a 4 MeV

electron Van de Graff, a 500 keV electrostatic electron accelerator, and a

1 MeV to 8 MeV pulsed electron linac. These are used in a variety of radiation

applications such as material modification, radiation-hardness testing, electron- and bremsstrahlung-beam

dosimetry, and HECT development.

New accelerator facilities, incorporating

machines currently used in medical

and industrial applications, are bringing

our programs to the forefront of

research and development. Installation

of a 6 MeV to 20 MeV electron-beam

(6 MV and 18 MV bremsstrahlungbeam) Varian Clinac 2100C to support

the development of direct, therapylevel dosimetry calibrations has been

completed. (See Fig. 5.)

Planning is underway for a facility based on two Titan 10 MeV, 17 kW electron

linacs, donated by the U.S. Postal

Fisure 5. NIST medical-therapy accelerator

facilit/.

Service, to support the standards and

calibrations program for homeland

security applications, general industrial

radiation processing, and the study of

radiation effects in materials.

CONTACT: DR. FRED B. BATEMAN

(301) 975-5580

fred.bateman@nist.30v

Calibration of Low-Energy

Photon Brachytherapy

Sources

Small radioactive "seed" sources used in

prostate brachytherapy, containing the

radionuclide '"^Pd, ^^H, or ^^'Cs, are

calibrated in terms of air-kerma strength

using the NIST Wide-Angle Free-Air

Chamber (WAFAC). The WAFAC is an

automated, free-air ionization chamber

with a variable volume, allowing

corrections to be made for passage of

the beam through non-air-equivalent

electrodes. Over 500 seeds of 32 different designs, from 18 manufacturers,

have been calibrated using the WAFAC

since 1999. (See Fig. 6.)

On-site characterization at seed manufacturing plants for quality control, as

well as at therapy clinics for treatment

planning, relies on well-ionization

chamber measurements. Following the

primary standard measurement of air- kerma strength, the responses of several

well-ionization chambers to the various

seed sources are determined. The ratio

of air-kerma strength to well-chamber

response yields a calibration coefficient

for the well-ionization chamber for a

given seed type. Such calibration coefficients enable well-ionization chambers

to be employed at therapy clinics for

verification of seed air-kerma strength,

which is used to calculate dose rates to

ensure effective treatment planning.

Fisure 6. Close-up view of a seed (illuminated

by a laser), mounted vertically on a rotating

post, ready for calibration on thie WAFAC

calibration range.

To verify that seeds of a given design

calibrated at NIST are representative of

the majority of those calibrated in the

past, several additional tests have been

implemented. The distribution of

radioactive material within a seed is mapped using radiochromic film contact exposures. The in-air anisotropy of

seeds is studied by taking WAFAC and

x-ray spectrometry measurements at discrete rotation angles about the long axis and the axis perpendicular to the midpoint of the long axis of the seed,

respectively. The "air-anisotropy ratio,"

calculated from the results of angular

x-ray measurements, has proven to be

a useful parameter for explaining differences in well-chamber response observed

for different seed models having the same emergent spectrum on their

transverse axis.

CONTACT: DR. MICHAEL G. MITCH

(301) 975-5491

michael.mitch@nist.sov

35
The strategy ofthe Time and Frequency Division is to advance measurement

science and to provide time andfrequency standards and measurement services

to commerce, industry, and the public.

Ihe first 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 stability essential for supporting U.S. commerce and scientific research; provides an official source of

time for U.S. civilian applications; and

supports coordination 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,

NIST-Fl. The time scale is an ensemble

of five (soon, six) hydrogen masers and

four 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 Aflf

approaching 6 x 10""^ (0.6 fHz/Hz,

as ofJune 2004).

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 contributing 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

four laboratories worldwide (as of late 2004) operating the highest accuracy

primary frequency standards to determine the frequency (rate) of UTC.

The extraordinarily stable NIST time

scale, coupled with world-leading per- formance of the NIST primary frequency standard (as of June 2004), provides

U.S. industry and science with a unique

resource for the most demanding applications of accurate time and frequency.

However, 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

Stan'dards

Since the first atomic clock was invented

at the National Bureau of Standards

(NIST's predecessor) in 1949, the per- formance 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 Positioning System

(GPS). NIST research on microwave

and optical frequency standards strives

to at least maintain this rate of performance improvement.

36
ACCOMPLISHMENTS

Improved Performance of

the NIST-F1 Primary

Frequency Standard

The NIST-F 1 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-F 1 frequency to the International

Bureau of Weights and Measures

(BIPM) in 1999, the NIST-F 1 uncertainty has been reduced by about a factor of three.

The NIST-F 1 frequency evaluation

reported to BIPM in June 2004 included an "in-house" fractional frequency

uncertainty of approximately 6 x 10~"^

(0.6 fHz/Hz), increasing to about

9 X 10 (0.9 flHz/Hz) as received

at BIPM due to uncertainties in the

satellite-transfer process. Both of

these results were, at the time, the

best ever reported to BIPM—by a

significant margin.

Ongoing NIST-F 1 changes continue to improve performance. New laser systems, for generating the optical molasses

and repumping, maintain frequency

lock for weeks without intervention.

Since NIST-F 1 data must be averaged

for about a month to achieve ultimate

uncertainties, this improvement has substantially reduced downtime. The higher

power molasses-laser system also permits

reshaping of the atom cloud to reduce

atom density in the vertical (launch)

direction, decreasing the spin-exchange

shift without loss in detected atom

number. Systems that ensure that

mechanical shutters fully block the lasers

Fisure 1. The NIST-F1 cesium fountain primary

frequency standard, tfie Nation's standard for

frequency and tine SI second.

have reduced the light-shift: uncertainty

by 50 %. Other improved systems

include 9.2 GHz microwave synthesis,

vacuum, temperature, computer

automation, and data transfer to the

time scale.

We are carefully exploring the role of

deadtime in precision frequency measurement and satellite transfer—that is,

time when the NIST maser ensemble

continues to operate, and potentially

drift, while the primary frequency reference is not operating. In addition to

purposely building deadtime into formal

frequency evaluations, the Division is

collaborating with the NIST Statistical Engineering Division to formally model

deadtime effects.

CONTACT: DR. STEVEN JEFFERTS

(303) 497-7377

jefferts@boulder.nist.gov

Second-Generation Cesium

Fountain Primary Frequency

Standard

While continuing to optimize NIST-F 1,

the Division is actively developing the

next-generation primary frequency standard, NIST-F2. The largest nonstatistical contributions to NIST-F 1 frequency

uncertainty are the spin-exchange shift.

due to cold atom collisions, and the

blackbody shift (AC Stark shift from

thermal radiation near 300 K). NIST-F2

is intended to substantially reduce those

uncertainties through two means.

First, 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 interrogation region.

This approach will minimize spinexchange shifts while still providing

sufficient atom numbers at detection

for good stability.

The general principles of this approach

have been successftilly demonstrated in NIST-F 1. To make the system practical,

NIST-F2 will use a low-velocity intense

source (U/IS) of atoms for the required

rapid cooling, capture, and launch of

many atom balls in succession. Early

results demonstrate molasses atom fill

rates of about 4 x 10^ s^Mn addition,

the fountain team has demonstrated

cooling to approximately 1 \iK using the

required (1,1,1) NIST-F2 fountain

geometry. Both these results are commensurate with NIST-F2 performance

requirements.

The second major improvement in

NIST-F2 will be to cool the drift tube

and interrogation 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.

37
TIME AND FREQUENCY DIVISION

The ultimate goal for NIST-F2 is to approach an "in-house" fractional fre- quency uncertainty of 1 x lO"'*^ in the

next few years.

CONTACT: DR. ELIZABETH DONLEY

(303) 497-5173

edonley@boulder.nist.gov

Research on Optical

Frequency Standards

While the ultimate accuracy limit of

cesium microwave standards operating

near 10"^ Hz is not yet clear, optical fre- quency 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 advantageous in many applications.

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 techniques of quantum

computing. A crucial part of optical

clock research is optical frequency synthesis using femtosecond laser frequency

combs, described in a later section.

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 1 00 or more. With a Q factor

> 10'^, and a transition that is relatively

insensitive to environmental factors, the

potential fractional frequency uncertainty Aflf for a mercury ion standard is as

small as 10"'^.

The reproducibility of the mercury ion

standard relative to the NIST-Fl primary frequency standard was studied

over a two-year period. Measurements

were referenced to NlST-Fl through a hydrogen maser, using a femtosecond

laser frequency comb to compare optical

and microwave frequencies. The mercury-ion optical frequency standard has

better short-term stability than NISTF 1 , so the stability of the maser was key

to the intercomparison.

The experiment set a limit on the

fractional frequency variation of the

NIST-Fl cesium microwave transition,

referenced to the mercury ion optical

transition, as no greater than ±7 x 10~'^

per year. From the point of view of the

cesium transition being defined as the

international frequency standard, this means the mercury ion clock frequency

is stable to this level.

This experiment 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 gQ^ { m^.! m^) a!^. Assuming any variation is due to a only,

this result sets an upper bound for the

fractional change in the fine-structure

constant as no greater than 1.2 x 10~'^

per year. It is a tighter bound by about a

factor of 30 than astronomical observations suggesting variations in the finestructure constant over periods comparable to the age of the universe.

CONTACT: DR. JAMES C. BERGQUIST

(303) 497-5459

berky@boulder.nist.gov

Fisure 2. The calcium-atom optical frequency

standard, beins adjusted by Chris Oates.

Calcium-Atom Optical

Frequency Standard

The calcium optical clock transition at about 657 nm (456 THz) has several

advantages. It is spectrally sharp

(470 Hz natural linewidth), can be

detected with excellent signal-to-noise

using shelving-detection techniques, and

is largely insensitive to perturbations

from external electric and magnetic

fields and from cold collisions.

The frequency of the calcium optical

clock transition has been measured to a

fractional uncertainty approaching

1 x 10~'^, making it one of the best- known optical frequencies. The 423 nm

resonance line permits rapid first-stage

laser cooling to the Doppler limit of

about 2 mK, and we have demonstrated

three-dimensional, quenched narrowline second- and third-stage laser cooling

to about 10 ^K. Experiments to slow

calcium atoms fiarther using pulsed,

one-dimensional, quenched narrow-line

laser cooling have reached temperatures

as low as 300 nK. (See Fig. 2.)

A calcium optical frequency standard

should ultimately demonstrate fractional

stability approaching 2 x 10~"^ with one second of averaging. Performance

comparable to cesium fountain micro- wave standards could be attained with

averaging over seconds, rather than

weeks.

38
TIME AND FREQUENCY DIVISION

It is likely that ion and neutral atom

optical standards will each display ulti- mate strengths and limitations. They

may find uses in different applications

in much the same way that different

microwave standards are optimal for

different applications—such as cesium

standards for absolute accuracy and

hydrogen masers for greatest stability.

CONTACT: DR. CHRIS OATES

(303) 497-7654

oates@boulder.nist.gov

I he second stratesic

focus is to develop and

operate the frequency and

time services essential for

synchronizins important

industrial/commercial operations and supportins 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,

transportation, 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. Collins, 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

Internet 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) serves industrial and research customers who need

tight traceability to NIST frequency

standards. FMAS customers receive continuous, real-time NIST traceability

through a highly automated system

remotely monitored by NIST, receiving

NIST frequency standards by compari- son to GPS broadcasts. The most

demanding customer needs are met

through the Global Time Service, which

uses GPS common-view time transfer to

deliver to the user's site a timing reference very close in accuracy to the NIST

time scale.

To enhance U.S. expertise in this field,

the Division offers a variety of training

courses. A 3)2 day metrology seminar is

offered annually, a new 3 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 courses at conferences.

ACCOMPLISHMENTS

NIST Internet Time Service

(ITS)

Fourteen ITS servers at eleven locations

across the Nation respond to about

1 Yi billion requests per day (as of sum- mer 2004) for setting computer and

network clocks to NIST time, automatically. (See Fig. 3.) The Division website

provides free client software, complete

1.6

Figure 3. Growth in use of the NIST Internet

Time Service.

39
TIME AND FREQUENCY DIVISION

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

Windows XP, Mac OS, and many

commercial versions of Liniuc.

The Division continually updates the

servers, software, and network infrastructure, working with the NIST net- working 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. It is likely that they will become

part of the national information infrastructure. For example, the U.S. Postal

Service Electronic Postmark program

places a secure, auditable timestamp on electronic documents referenced to NIST time, and stores these documents on secure servers for parties in a transaction to examine and exchange as legal

documents.

CONTACT: DR. JUDAH LEVINE

(303) 497-3903

jlevine@boulder.nist.30v

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, including systems to ensure automatic recovery from power failures or

Figure 4. An aerial view of tine WWVB antenna

systems.

loss of primary transmitters when station staff are not present; continuing

replacement of WWVH metal antenna

towers, subject to corrosion from sea

salt, with fiberglass towers hinged to permit bending the tower to the ground

for easy and safe maintenance; and

upgrading insulators in the guy wires

supporting the eight 122 meter

(400 foot) towers for the WWVB

antennas (Fig. 4).

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 a monitor sys- tem to measure received power from

WWVB broadcasts, and several of these

systems were constructed on contract. We plan to place them at strategic locations around the U.S. Through an

Internet connection, each will continuously report back the WWVB signal

strength to the Division. The results will

be displayed on a publicly available website, along with archives of all signal

strength records.

We have been actively consulting with

WWVB-controlled timepiece manufacturers to improve their product performance. The monitoring data will help

manufacturers set performance specifications for real-world signal strengths.

Consumers can also consult the website

to determine if problems with their

timepieces result from inadequate

WWVB signals or, as is almost always

the case, from problems with the timepiece itself

The Division is publishing a "Recommended Practices for Manufacturers and Consumers of

WWVB Radio Controlled Clocks"

guide, developed in consultation with

manufacturers and enthusiast user

groups, which suggests practices to

ensure optimal timepiece performance.

CONTACT: MR. JOHN P. LOWE

(303) 497-5453

lov^e@boulder.nist.gov

^^^e third strategic focus

is to develop new measurement systems and methods

in support of emersing

technolosies.

New Measurement

Systems and Methods

INTENDED OUTCOME AND

BACKGROUND

In addition to meeting current customer

needs, the Division prepares for the

future of time and frequency measure- ments and calibrations. Through interactions and discussions with constituents, we identify important emerging requirements and technologies. We

40
TIME AND FREQUENCY DIVISION

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 fre- quency 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 previously possible, and to direct comparison

of microwave and optical frequency

standards, bridging five decades in frequency. We are working on techniques

for amplification, noise reduction, and

applications across difi^erent frequency

ranges, such as the important nearinfrared 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, to dramatically improve

the performance of small electronic

devices such as GPS receivers and wireless communications devices. Such chipscale atomic clocks need not be as accurate or stable as large laboratory standards, but they will bring atomically

Figure 5.

Scott DIddams with

a femtosecondlaser-based optical

frequency synthesizer system.

precise timekeeping 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 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

frequency output given an optical fre- quency reference input. This remarkable

capability is crucial to the development

and dissemination of useful optical fre- quency standards. As mentioned, the

Division and other laboratories have

used optical frequency combs to directly

compare the cesium fountain microwave

frequency (9.2 GHz) with optical frequencies from the calcium atom stan- dard (456 THz) and the mercury ion

standard (doubled 532 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. (See Fig. 5.) The Division also collaborates with the NIST

Electronics and Electrical Engineering

Laboratory to develop Cr:fosterite femtosecond lasers, operating in the nearinfrared from about 1.0 \im to 2.2 [am,

including the important 1 .4 pm to

1 .6 pm optical telecommunications

band.

An indication of progress is the recent

Division-led frequency intercomparison

of four different femtosecond laser frequency synthesizers, from three

laboratories, using two fundamentally

different comb-generation techniques,

broadband operation and nonlinear

microstructure fiber. Three frequency

synthesizers—one each from the

International Bureau of Weights and

Measures, East China Normal

University, and the Division—were compared to a second Division one,

41
TIME AND FREQUENCY DIVISION

referenced to a 456 THz optical fre- quency standard. Comparisons were conducted for a total of six days spread

across several months.

The frequency differences, determined

by optical heterodyne techniques, were measured to a relative uncertainty of

1.4 X 10~'^, with the uncertainty arising primarily from mechanical and ther- mal effects and limits on integration

time. The results suggest optical fre- quency combs can be reliably used for frequency comparisons and synthesis to

at least a fractional uncertainty of 10"^',

and likely better when technical noise

(mechanical and thermal fluctuations)

are better controlled and longer integration times are used.

CONTACT: DR. SCOH A. DIDDAMS

(303) 497-7459

sdiddams@boulder.nist.sov

Chip-Scale Atomic Clocl<

Division research on a miniature, alloptical atomic clock, based on coherent

population trapping, stimulated DARPA

interest in developing a chip-scale atomic clock (CSAC). Program goals are to

bring atomically precise timing and

frequency control to applications in

portable electronic devices, such as enhanced GPS receivers and better

performing wireless communications

devices for improved communications

security. The overall goals of the

DARPA program are to develop a CSAC of 1 cm^ total volume, consuming no more than 30 mW of power

with a fractional frequency stability of

about 1 X 10"^' over one hour.

Figure 6. Photomicrograph of the physics

pacl<age of a NIST chip-scale atomic clocl<,

with a schematic diagram.

NIST is part of a DARPA-funded

CSAC consortium of eight companies

and universities. The Division is charged

with providing the fundamental research

and metrology, with the expectation that

companies will develop the commercial

products.

The Division has recently demonstrated

a prototype CSAC with a physics package smaller than 0.01 cm^, a fractional

frequency instability of about

2.5 xlO~" at 250 seconds integration,

and a power consumption of about

75 mW (Fig. 6). These parameters are

believed to be best in the world, and are approaching the stringent DARPA

goals. The Division understands what

modifications are needed to significantly

improve the frequency stability and

reduce the power consumption, and is

optimistic that the DARPA goals can be

met relatively soon.

The Division has collaborated with the

NIST Electronics and Electrical Engineering Laboratory to use standard

MEMS fabrication techniques in making the CSAC physics package, suggesting that CSACs based on the Division

model could be mass-produced at

relatively low cost, using wafer-level

assembly techniques. Such a process would enable the extremely broad application of CSACs in portable electronic

devices, for many applications.

The Division is also exploring the possibility of using CSAC technology to make tiny magnetometers approaching

the sensitivity of SQUIDs, without

the need for cryogens, and for other

applications.

CONTACT: DR. JOHN KITCHING

(303) 497-4083

kitchins@boulder.nist.30v

^^^e fourth strategic focus

is to develop quantum-logic

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

Processins Using

Trapped Ions

INTENDED OUTCOME AND

BACKGROUND

We conduct research on the development and properties of prototype quantum-logic devices consisting of small

numbers of electromagnetically trapped

and laser-cooled ions serving as quantum bits (qubits). This research comprises quantum computing, quantum

measurement (including noise reduction

in frequency standards), and develop42
TIME AND FREQUENCY DIVISION

ment of new classes of quantum-logicbased 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 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 funding

agencies. Our unique expertise in quantum state engineering has made the

trapped-ion quantum computing program a world-leading effort.

But the Division work on quantum

state engineering also directly serves our

time and frequency metrology mission.

For example, we recently 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

required 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.

Division researchers demonstrated the

ability to sympathetically laser-cool ions

of different species in a trap. In one

experiment, a two-ion crystal consisting

of a ^Be* ion and a ^'*Mg* ion was

cooled by laser irradiation on only one

ion. The laser-cooled "refrigerant" ion

sympathetically cooled the other ion

through the Coulomb interaction, but

because transitions in the two ions were

separated by some 30 nm in wavelength, irradiation of one ion had no

direct effect on the other.

This property enables an entangled pair

of ions of different species to be laser

cooled without perturbing the qubit

information. Such a process could be

very useful in a complex, multi-ion

quantum computing architecture, where

motional heating from quantum state

manipulations must be removed without perturbing qubit states.

Sympathetic cooling also broadens the

range of ions that can be used as potential frequency standards. For example,

^^Al + has potentially good clock transitions but no easily accessible laser cooling transitions. The Division is investigating the potential of a ^^Al+ frequency

standard using ^Be* sympathetic cooling

and entangled state spectroscopy.

Division researchers have conducted

many experiments demonstrating the

effectiveness of various logic gates and

demonstrating quantum computing

architectures that are, in principle, completely scalable—based on ions manipulated by lasers and multi-zone traps.

Division researchers also demonstrated a

robust, high-fidelity logic gate based

only on changes of phase in a rwo-ion

^Be* system. (See Fig. 7.)

Recently, Division researchers demonstrated deterministic quantum teleportation of qubits in a three-ion trap. A

coherent superposition of two internal

states was generated in one of the ions,

and then the quantum states were teleported to a second ion through a third,

intermediary ion. This experiment and a

similar one simultaneously reported by a group from Innsbruck were the world's

first demonstrations of teleportation of

massive particle qubits, rather than phoFisure 7. David Wineland adjustins one of

the systems used for studying quantum-logic

gates.

ton qubits. Quantum teleportation

could be crucial to realization of a largescale quantum computer, enabling rapid

transmission of qubit information

throughout the computer without the

need to physically move qubits.

CONTACT; DR. DAVID J. WINELAND

(303) 497-5286

wineland@boulder.nist.gov

43
The first strategic element

is to develop precision

measurement tools and

applications.

Precision

Measurement

INTENDED OUTCOME AND

BACKGROUND

The Quantum Physics Division continues a leadership role in developing new

precision-measurement techniques and

applications. Precision measurement is

used for many industrial and scientific

purposes, and is central to many activities of NIST and other standards laboratories. Applications range from providing the length scale for mechanical

measurements to providing a direct

connection between optical and radio

frequencies.

QUANTUM PHYSICS DmSION

The strategy ofthe Quantum Physics Division is to help produce the next generation ofscientists 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.

The highly stabilized laser, a Division

specialty, is the workhorse of precision

measurement. Traditionally, this meant

continuous wave (CW) lasers that generated 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. These

generate wideband "comb" spectra, consisting of long series of sharp spectral

lines. Each such line can have individually a very precise and stable frequency,

with their frequency separation constrained to be the repetition rate of the

laser. This rate may be locked to a

radio frequency (RP) reference

(e.g., microwave).

Frequency combs significantly advance

the art of measuring optical frequencies

and establish a direct connection

between optical and radio frequencies.

This connection enables optical atomic

clocks and absolute optical frequency

metrology.

ACCOMPLISHMENTS

Advances in Frequency

Comb Technology

Early progress in comb techniques was

enabled by the development of

microstructure optical fiber, which combines high nonlinearity with low dispersion to allow strong nonlinear broadening of weak pulses. It broadened the

output of mode-locked lasers to the

point where the spectra included comb

lines that were twice the frequency of

other comb lines—a full octave, in

musical terms. However, microstructure

fiber has significant drawbacks, including coupling into its 2 pm core, drift:

of the coupling over time, facet damage, and amplitude-to-phasenoise conversion.

Figure 1 . The Quantum Physics Division's newest

hires, Ralph Jiminez (I) and Konrad Lehnert (r).

44
To eliminate the need for microstructure fiber, we built a mode-locked

Ti:sapphire laser that directly generates

an octave-spanning spectrum. We

demonstrated that its offset frequency

could be locked using self-referencing.

Self-referencing has been the principal

technique used to control the offset fre- quency of the comb. One compares the

high- and low-frequency wings of an

octave-spanning comb, and frequencylocks a line with its double. It is typically implemented as a bulk-optic

interferometer.

Recently, we have measured and controlled the offset frequency using quantum interference of injected photocurrents in a semiconductor. This technique uses quantum rather than optical

interference. It replaces a bulk optical

interferometer with a single semiconductor chip, which is smaller, less

expensive, and less complicated. The

phase stability, as measured by an outof-loop, standard self-referencing interferometer, was as good, or better, than

that achieved using the standard selfreferencing technique.

CONTACT: DR. STEVEN T. CUNDIFF

(303) 492-7858

cundiffs@jila.colorado.edu

New Implementation of an

Optical Molecular Clock

An optical "atomic" clock uses as its reference an optical frequency transition

that has a lower relative frequency

uncertainty than does the standard,

cesium microwave frequency transition.

An optical clock phase-coherently

derives an RF signal from the optical

frequency standard, which can be done

with a mode-locked laser.

We have built an optical molecular

clock, based on difference-frequency

generation that does not rely on an

octave-spanning spectrum, microstructured fiber, additional CW lasers, or

stabilization of the offset frequency. We

stabilize a HeNe laser at 3.39 pm wavelength using the methane F2(2) line. This laser serves as the infrared optical

frequency standard to which the

repetition rate of a Tirsapphire laser is

phase-coherently locked. We use the

mode-locked laser's frequency comb for

difference-frequency generation to provide an infrared comb at 3.39 pm with

a null carrier-envelope offset. This

infrared comb phase-coherently links

the 88 THz optical reference and the

repetition rate.

Comparison of the repetition rate signal

with a second frequency comb stabilized

to molecular iodine shows an instability

of 0.12 pHz/Hz at 1 s, limited by

microwave detection of the repetition

rates. The single sideband phase noise of

the microwave signal, for a 1 GHz carrier frequency, is below -93 dBc/Hz at

1 Hz offset.

CONTACT: DR. JUN YE

(303) 735-3171

ye@jila.colorado.edu

Novel Spectroscopy of Cold

Atoms

Historically, stabilized CW lasers have

been integral to spectroscopy; frequency

combs from mode-locked lasers served

as reference rulers for wavelength.

However, frequency combs also enable

vastly improved measurement of atomic

and molecular structural information.

The combination of frequency domain

precision with time domain dynamics

establishes a new paradigm for spectroscopy, connecting the fields of precision measurement and ultrafast science.

We recently demonstrated direct,

precision spectroscopy of global atomic

structure using a single, stabilized optical frequency comb. This approach

exploits massively parallel spectral probing in the frequency domain. The widebandwidth, phase-coherent, absolutefrequency-referenced comb allowed us

to precisely measure atomic energy level

structure in the optical, terahertz, and

radio frequency domains at the same

time, with a systematic-error-free connection among all spectral features. Furthermore, the pulsed excitation permits time-resolved studies of dynamics

and real-time monitoring and control

of both optical and quantum-coherent

interactions and state transfer.

In a real sense, we have merged the

fields of precision spectroscopy and

coherent control. At short times, we

monitor and control coherent accumulation and population transfer. At long

times, we recover all the information

pertinent to atomic level structure at a

resolution limited only by the atomic

linewidth. The spectroscopic precision

we have achieved with a frequency

comb rivals that of the state-of-the-art CW laser-based approaches, even

45
QUANTUM PHYSICS DIVISION

(a) (b)

•

Figure 2. Imases showing strontium atoms forming a "cube" as the frequency of the laser light used to

manipulate them changes, (a) Atoms become visible at the eight corners of a cube, (b) Atoms also

appear at the midpoints of the cube edges and begin appearing at the center of each face, (c) Atoms

appear more clearly at the centers of each cube face.

though our measurement covers a fre- quency range of hundreds of terahertz

with a single laser.

Additionally, we have experimentally

demonstrated the frequency comb's

mechanical action on cold atoms.

Precise control of the frequency and

phase of the entire comb spectrum

allows us to apply a light force on

probed atoms without accumulating significant effects from heating or Doppler

shifts. We exploit this mechanical cooling for spectroscopy, significantly reducing systematic errors. The flexibility in

the comb structure also allows us to

carefully measure and control the

AC Stark shift inevitably present in

light-atom interactions.

Our research on ultracold strontium

atoms has three main thrusts: optical

atomic clocks, ultracold collisions, and

quantum degeneracy. Thus far, we have

obtained new insights to laser-cooling

mechanisms by using the nuclear-spin

magnetic degeneracy of cold Sr atoms

to obtain strong sub-Doppler cooling,

despite a closely overlapped excited state

manifold.

We have demonstrated several unique

aspects of a magneto-optic trap supported by narrow-line cooling, including

achieving a subrecoil temperature of

250 nK (the recoil temperature is 450 nK) for the first time without needing atomic coherence in the ground

state. At such low temperatures, the

atom cloud displays interesting dynamics. For example, if we tune the trapping

laser frequency above the atomic resonance, the cloud divides into discrete

momentum packets resembling lattice

sites on a face-centered-cubic crystal.

(See Fig. 2.)

Precision spectroscopy on ultracold Sr

has also begun. We have determined the

absolute frequency of the Sr transition

to a 25 Hz uncertainty. We have also

observed a density-related frequency

shift and linewidth broadening for

alkaline earth atoms. This will be valuable information for understanding the

collision dynamics of these atoms in a

quantitative manner.

CONTACT: DR. JUN YE

(303) 735-3171

ye@jila.colorado.edu

Fast, Ultrasensitive

Bolometers and Calorimeters

The emerging fields of quantum computing and quantum cryptography

require fast, energy-resolving photon

counters (calorimeters). At the same

time, future space-based observatories

will require imaging arrays of thousands

of ultrasensitive bolometers, k is

impractical to read-out each of these

sensors with its own amplifier. Thus,

the ability to multiplex the sensors, i.e.,

to read-out many sensors with one

amplifier, is paramount.

We have built sensors that can be configured as either fast calorimeters or sensitive, multiplexible bolometers. The

incident power or energy is inferred

from the resistance of a nanoscale thermistor formed from normal metal-insulator-superconductor junctions.

Recent measurements show that our

sensor is fast enough to count photons

in submicrosecond times and sensitive enough to detect an incident power of

7 X 10~'^ watts in one second, when

operated at 270 mK.

The key innovation relies on measuring

the temperature-dependent resistance

using a microwave technique compatible

with subkelvin operating temperatures.

The sensors can be configured either for maximum speed, in which case they are

calorimeters, or for slower, multiplexible

operation, in which case they are sensitive bolometers. By optimizing the sensors and operating them at a temperature of 50 mK, we anticipate bolometric

sensitivities of 10~^^ W/Hz^'^, meeting

the requirement of the most demanding

fliture space missions.

CONTACT: DR. KONRAD LEHNERT

(303) 492-8348

Iehnertk@jilau1 .colorado.edu

46
QUANTUM PHYSICS DIVISION

Gravity Measurements

We measure the Newtonian constant

of gravity, G, and the acceleration of

gravity, g. To measure G, we directly

compare the attraction of a laboratory mass to the attraction of the Earth. Our

experiment translates length changes

due to gravity into measurable beat fre- quency changes between two lasers. We expect our final measurements to

yield a relative uncertainty for G of

about 4 X 10-5.

We are also developing a new, compact

instrument to measure the acceleration

of gravity, g. The instrument employs a

novel cam-based mechanism to obtain

extremely fast and quiet control of the

entire release, freefall (measure), catch,

and lift cycle. It can be used for volcanology and precision-measurement

studies, and has an uncertainty of

approximately 3 [iGal (relative uncertainty of 3 X 10"^).

CONTACT; DR. JAMES E. FALLER

(303) 492-8509

fallerj@jila.colorado.edu

^j'he second strategic

element is to exploit BoseEinstein condensation, quantum desenerate Fermi sases,

and cold molecules for

metrolosy and ultralowtemperature physics.

Ultracold Atoms and

Molecules

INTENDED OUTCOME 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 BoseEinstein condensate by Eric Cornell

(NIST) and Carl Wieman (CU), who

together received the 200 1 Nobel Prize

in Physics. This achievement, coupled

with the creation of the first quantum

degenerate Fermi gas and the first Fermi

condensate by MacArthur Prize-winner

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 ultracold molecules also promises important

advances in chemical physics.

ACCOMPLISHMENTS

BEC on a Chip

We have succeeded in creating an atom

interferometer on a lithographically patterned microstructure, an "atom chip."

The long-term technical goal of this work is to develop supersensitive and

compact inertial sensors, e.g., gyroscopes

and gravity gradiometers.

A condensate of ultracold atoms is guided along an invisible magnetic track

generated by currents carried in tiny

wires. The condensate is split coherently

into two parts that travel a short distance in opposite directions along the

track. Then the directions are reversed,

the two parts of the condensate recombine, and we observe patterns of high

and low density—atom-wave interference fringes. The patterns of these

fringes are sensitive to any acceleration

felt by the chip during the period when

the two parts of the condensate were

separated.

In this first realization, the sensitivity

is limited by the relatively short time

the condensate parts remain separated.

Future work will concentrate on

improving performance.

CONTACT: DR. ERIC A. CORNELL

(303) 492-6281

cornell@jila.colorado.edu

47
QUANTUM PHYSICS DIVISION

Destroying BEC

Ironically, one of the more important

scientific advances in our recent ultracold research is progress towards

destroying a Bose-Einstein condensate.

As a ball of Bose-condensed gas starts to

rotate, it becomes pierced by progressively more tiny tornadoes knowrn as quantized vortices. When the rotation

rate is very high, these vortices organize

themselves into a tightly packed triangular array. At the highest level of rotation,

the size of each vortex becomes large

compared to the spacing between them.

Theory predicts a reordering transition

in which the condensate is destroyed

and replaced by a highly correlated gas,

reminiscent of the quantum Hall state

in solids. Achieving and characterizing

this transition is a prime scientific goal

because we believe it will generate

important insights into analogous transitions in technologically important,

condensed-matter systems, such as the

giant-magnetoresistance phenomenon

that is used in disk-drive read-sensor

technology.

In the last two years we have come much closer to achieving our goal. We

have installed high-intensity lasers that we hope will soon bring us even closer.

CONTACT: DR. ERIC A. CORNELL

(303) 492-6281

cornell@jila.colorado.edu

Cold Fermions and

Resonance Superfluidity

Our work on cold Fermi gases has progressed at a rapid pace. In January 2004,

we reported the first observation of a "Fermi condensate." This novel phase of

matter was predicted in 2001 by JILA's Murray Holland (CU), who coined the

term "resonance superfluidity" because

of the key role of a magnetic-field

Feshbach resonance in creating these

condensates of fermionic-atom pairs.

Our experimental observation, which

included a measurement of the temperature and magnetic-field phase diagram,

revealed a surprisingly high transition

temperature (relative to the Fermi temperature). It triggered a great deal of

experimental and theoretical work

exploring this new Fermi superfluid

phase. Because of the unique control

we have in ultracold gas systems, future

studies of the Fermi condensate have

the potential for dramatically enhancing

our understanding of the connection

between superconductivity and

Bose-Einstein condensation.

Progress leading up to the Fermi-condensate observation yielded a number of

important advances, including the first

spectroscopic measurements of the interaction energy in a Fermi gas near a Feshbach resonance, the first reversible

conversion (pairwise) of the majority of

trapped ultracold atoms into ultracold

molecules, and a direct measurement of

the binding energy of these molecules

with the introduction of RF photodissociation.

CONTACT: DR. DEBORAH JIN (303) 492-0256

jind@jila.colorado.edu

Fisure 3. MacArthur Prize-winner Deborah Jin,

witli lier CU sraduate student Cindy Resal and

CU postdoctoral research associate Marcus

Greiner.

Bose-Fermi Mixtures

We are now exploring Bose-Fermi mixtures. We employ sympathetic cooling

to produce Bose-Einstein condensates of

^^Rb atoms simultaneously trapped with

a Fermi gas of '^''K atoms.

Focusing on interactions in the gas mixture, we perform collision studies to measure the magnitude of the interspecies scattering length between the

^^Rb and atoms. This single parameter characterizes the interactions

between the boson and fermion atoms

and thus controls many of the equilibrium and dynamic properties of the ultracold gas mixture. By using an optical

dipole trap and manipulating the atoms'

spin states, we recently observed four

heteronuclear Feshbach resonances.

These resonances open up the possibility

for controlling the interactions in the

gas. They also provide a means for creating ultracold, weakly bound heteronuclear molecules.

CONTACT: DR. DEBORAH JIN (303) 492-0256

jind@jila.colorado.edu

48
QUANTUM PHYSICS DIVISION

third strategic

element is to advance

ultrafast science.

Ultrafast Science

INTENDED OUTCOME 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 modelocked 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 dynamics of

electron spins in semiconductors and of

biomolecides, providing technologically

important information for both optoelectronics and biotechnology. We use

phase stabilization to improve measure- ment techniques and to develop radical

new ultrafast technologies, such as

"gainless" amplification of femtosecond

pulses in a buildup cavity.

ACCOMPLISHMENTS

Passive Optical Cavity

Interactions with a

Femtosecond Comb

We have directly stabilized a modelocked laser's optical frequency comb

to a high-finesse passive optical cavity.

We made detailed comparisons of two

stabilization schemes to optimize cavity

stabilization and to develop approaches

for overcoming limitations on transfer of the cavity's frequency stability to the

microwave domain. We explored the

stability of the frequency comb in both

the optical and the radio frequency

domains.

With an independent, stable CW laser, we verified that the linewidth and stability of the frequency comb components

are <300 Hz and 50 fHz/Hz at 1 s averaging time, respectively, both limited by

the CW laser. Such performance represents the state of the art in frequency

and phase stabilization of a modelocked laser. It confirms that a highly

stable, passive optical cavity can directly

stabilize the repetition frequency and

carrier-envelope phase of ultrashort

pulses to a level rivaling that achieved by

CW lasers.

We also demonstrated a technique for enhancing femtosecond pulses from a

pulse train via coherent buildup in a

high-finesse cavity. By periodically

extracting the intracavity pulse, we

increased the net pulse energy 42-fold

to 70-fold. Pulse energies of >200 nj were demonstrated. Greater single-pulse

amplification is achieved using higher

finesse cavities at the expense of a reduced repetition rate.

We also developed a measurement

protocol for mirror dispersion. The

measurement accuracy is more than ten

times better than the previous state-ofthe-art, white light interferometry technique. We provided these precise measurements to the mirror manufacturer,

enabling them to significantly improve

their ability to make large-bandwidth,

low-loss, and low-dispersion mirrors.

CONTACT: DR. JUN YE

(303) 735-3171

ye@jila.colorado.edu

Spin Coherence in

Semiconductors

The possibility of using electrons' spin

degree-of-freedom for encoding information has attracted significant attention. This technology could lead to

devices analogous to traditional

microelectronics or to others based on quantum information concepts.

Optical techniques are currently the best

way to prepare and probe spin-coherent

states, as true "spintronic" devices are

still very primitive. Optical preparation

and probing are also likely to be

preferred for quantum information

applications.

We are acquiring a basic understanding

of how optical excitations in semiconductors manifest themselves in traditional optical techniques that excel at measuring the ^-factor, which determines how the electron precesses and its

spin coherence time, which limits duration of any operation. However, interpretation of the results requires knowledge of the difi^erent optical excitations

created by the incident pulses. In semi49
QUANTUM PHYSICS DIVISION

conductors, these include free electronhole pairs, excitons (bound electron-hole

pairs), biexcitons (two excitons bound

together, analogous to a hydrogen molecule), and trions (an exciton bound to an electron). Trions are particularly

important because they occur in materials containing excess electrons, which

can have long spin coherence times.

We are exploring ways to control the

number of excess electrons to determine

why their presence increases the spin

coherence time. The most promising

technique is the use of special quantum

wells, where the spatial separation of the

electrons and holes results in a very long

recombination time, which means that

significant densities can be achieved

with modest powers.

CONTACT: DR. STEVEN T. CUNDIFF

(303) 492-7858

cundiffs@jila.colorado.edu

Optical Two-Dimensional

Fourier-Transform

Spectroscopy of Excitons

The concept of multidimensional

Fourier-transform spectroscopy was

originally developed in nuclear magnetic

resonance. This powerful technique

excels at elucidating coupling between

resonances.

We have developed an optical twodimensional Fourier-transform spectrometer to study coupling between

optical excitation in semiconductors,

specifically between excitons and electron-hole pairs. The results are providing insight into the many-body physics

that underlies the interactions between

the carriers. Specifically, it allows a

direct mapping of the real and imaginary parts of the self-energy. The selfenergy is a firndamental quantity that can be directly calculated using manybody theory, which, in turn, is used to model optoelectronic devices such as diode lasers.

CONTACT: DR. STEVEN T. CUNDIFF

(303) 492-7858

cundiffs@jila.colorado.edu

^^^e fourth strategic

element is to investisate

biolosical systems at the

sinsle-molecule level.

Biophysics

INTENDED OUTCOME AND

BACKGROUND

The Quantum Physics Division investigates important biological systems at the

single-molecule level, thus leveraging our measurement expertise and experience 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 biophysics.

The Divisions strengths are the foundation of our efforts to contribute to groundbreaking research on single biomolecules. 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 attracts 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 Department of Chemistry, at the University

of Colorado. By integrating additional

departments into JILA, we will enhance

the very productive, interdisciplinary

character of the institute. Most importantly, because of our existing expertise, our biophysics program should rapidly

build on the successes achieved by our

other programs.

ACCOMPLISHMENTS

Single-Molecule Fluorescence

Microscopy: Biomolecular

Conformational Dynamics

This biometrology project probes conformational dynamics (e.g., folding and

unfolding) of biomolecules in chemically active states. We focus on simplifying

complex RNA structures to understand

the mechanisms that stabilize specific

structural folds. This information is

crucial to understanding RNA-based

enzymes, or ribozymes.

We use ultrasensitive time-, color-, and

polarization-resolved fluorescence detection of single RNA molecules in a confocal microscope. A mode-locked laser is

focused into an aqueous, dilute sample

of RNA molecules, with less than a single molecule in the detection region.

The resulting weak fluorescence is sorted

by both polarization and color, and is imaged onto single-photon-counting

avalanche photodiodes. The individual

photon events are recorded as a ftinction

50
QUANTUM PHYSICS DIVISION

of time after the incident laser pulse,

achieving an 1 1 order-of-magnitude

range of kinetic time scales.

The fast-fluorescence behavior monitors

the local environment of the RNA and

can be extracted via time-correlated, single-photon counting. Using fluorescence

resonant energy transfer (FRET), we

can measure distances (2 nm to 8 nm)

between specifically labeled sites on the

RNA. This allows us to investigate the

folding kinetics for RNA in real time at

the single-molecule level.

Thus far, studies have required tethering

the RNA to a glass coverslip. To eliminate possible surface effects, we are

developing methods for studying "free" RNA by exploiting "burst-mode" singlemolecule microscopy. This technique

detects species diffusing into and out

of the confocal region, but it limits the

time that we can probe single biomolecules. Consequently, we are also working on methods to slow down diffusion.

We plan to isolate single RNA molecules in liposomes, which could be

manipulated by optical tweezers and

viewed microscopically for arbitrary

lengths of time.

CONTACT: DR. DAVID NESBIH

(303) 492-8857

djn@jila.colorado.edu

Sinsle-Biomolecule

Electrophoresis

We have begun exploring single-molecule electrophoresis. The apparatus for

these studies is based on wide-field

microscopy through a thin gel-electrophoresis cell. In this technique,

weak electric fields are used to coax

single DNA molecules through a

micrometer-scale field of view.

The DNA motion can be studied by

labeling it with highly fluorescent dyes

that are illuminated by a laser and

detected by imaging on an intensified

CCD-array camera. This method is sensitive enough to image at a 10 Hz frame

repetition rate, and allows us to monitor

single-DNA electrophoresis dynamics in

real time.

We can automatically determine the

location of the DNA as a function of

time, and thereby track its progress and

mobility during electrophoresis. These

studies permit direct visualization and

detailed tests of biopolymer percolation

dynamics. In the future, they will help

us to learn more about improving separation efficiency and the kinetics/

dynamics of protein-DNA binding.

The latter are relevant to cell regulatory

processes and would be amenable to

study at the single-molecule level.

CONTACT: DR. DAVID NESBIH

(303) 492-8857

djn@jila.colorado.edu

Single-Molecule

Measurement v/ith

Nanometer Resolution

We are studying molecular motors at

the level of single molecules. Our efforts

are prompted by the insight that motor

proteins generate measurable force and

displacement.

Determining the elementary step size of

motor proteins is crucial to understanding their mechanisms. The enzymes

involved in DNA replication, DNA

transcription, and RNA translation

work, in a literal sense, as molecular

motors; once bound to their nucleic

acid substrates, they translocate in a

more-or-less unidirectional fashion.

E

,c, com

o

D.

146 148 150 152 Time [s]

154

Fisure 4. Individual 0.4 nm steps measured in

a new differential back-focal-plane detection,

optical-trapping microscope. The fact that the

data points lie on lines demonstrates that

0.1 nm stability is achieved over several

seconds.

carrying out hundreds to millions of

enzymatic cycles.

We have recently developed an instrument with subnanometer spatial resolution that has significantly improved the

displacements that optical trapping

experiments can detect. (See Fig. 4.)

Besides studying DNA-based molecular

motors, such as helicases, we are using our new subnanometer technology to

study transcription factors, which bend

DNA rather than moving along it.

Transcription factors turn on and off

the production of messenger RNA

and thereby protein expression.

We are also starting a new program to

study the unfolding of single molecules

of RNA. This work will bring together

JILA's expertise in laser and precision

measurement with CU's expertise in RNA research.

CONTACT: DR. THOMAS T. PERKINS

(303) 492-5291

tperkins@jilau1 .colorado.edu

51
GOAL

TO COORDINATE

AND FACILITATE THE

ELECTRONIC

DISSEMINATION OF

INFORMATION VIA THE

INTERNET

OFFICE OF ELECTRONIC COMMERCE IN

SCIENTIFIC AND ENGINEERING 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 ofscientific and engineering data.

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 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

NIST Standard Reference Data Program

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 1 994, 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 items. For the

most recent six months, there was an

average of 1/4 million requests for web

pages per month from the Gaithersburg

server (nearly half from about 30 online

databases containing physical reference

data). A complete list of our databases is

available at http://physics.nist.gov/data.

Recent work includes the development

of new (1-5) and updated (6-11) Web

databases:

1 . Handbook of Basic Atomic

Spectroscopic Data

2. Energy Levels of Hydrogen and

Deuterium

3. Spectral Data for the Chandra

X-Ray Observatory

4. X-Ray Transition Energies

5. Potential Energy Surface Database

of Group II Dimer Molecules

6. Fundamental Physical Constants

7. Searchable Bibliography on the

Constants

8. NIST Atomic Spectra Database

9. Electron-Impact Cross Sections for

Ionization and Excitation Database

10. X-Ray Form Factor, Attenuation,

and Scattering Tables

1 1 . Frequencies for Interstellar Molecular Microwave Transitions

ACCOMPLISHMENTS

Units Markup Lansuase

We have continued to develop an XML

(extensible Markup Language) schema

for encoding scientific measurement

units. Adoption of this schema will

allow the unambiguous exchange of

numerical data over the Internet. We

have established collaborations with

Lawrence Berkeley National Laboratory,

Mathsoft, an engineering software company, and SEMATECH, a consortium

of the semiconductor industry.

To complement the UnitsML schema, we are in the process of developing an XML repository containing detailed

information on both SI and non-SI

scientific units. We anticipate this repository will be used by our customers to download industry-specific dictionaries

of scientific units. Development of the

UnitsML schema, repository, and a

general ontology for scientific units

is supported in part by the NIST

Systems Integration for Manufacturing

Applications (SIMA) program.

CONTACT: DR. ROBERT DRAGOSET

(301) 975-3718

robert.dragoset@nist.sov

52
Support for ITL on the DLMF

We are providing support to the Mathematical and Computational Sciences

Division of the NIST Information

Technology Laboratory (ITL) to develop

the Digital Library ofMathematical

Functions (DLMF). Abramowitz and

Steguns Handbook ofMathematical

Functions (with Formulas, Graphs, and

Mathematical 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

account for over half its length. It also

lacks the many recent developments in

the theory and computation of fonctions that find essential use in physics

and other sciences. A project is underway to develop a replacement, which

should become a major resource of math

reference data for special fianctions and

their applications. The new DLMFW\]X

appear in a hardcover edition and as a

free electronic publication on the Web.

The Office of ECSED has a strong

capability in LaTeX, a powerfial, complex typesetting language particularly

useflil for representing mathematical

expressions. Since the DLMFis being

prepared in LaTeX, we are providing

support to ITL on the preparation of

this publication. This entails editing

existing chapters with extensive handwritten corrections, in addition to 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 have

thus far worked on 23 of the 40 chapters. The hardcover edition will be over 1000 pages in length and is scheduled to be printed in 2005.

CONTACT: GLORIA WIERSMA

(301) 975-5547

Sloria.wiersma@nist.sov

f ^ .

I CtmT^ "** Electron-lmpa Electron-Impact Cross Sections

for Ionization and Excitation

Figure 1 . Karen Olsen and Gloria Wiersma discuss the design of an online database.

New Capabilities for On-Line

Databases

The Electron-Impact Cross Sections for

Ionization and Excitation Database has

been available on the Web since August

1997. We recently collaborated with the

Atomic Physics Division to update the

database and release Version 3.0.

Additions to the database include: excitation cross sections for atoms H, He,

and Li; and ionization cross sections for atoms B, C, N, O, Al, Ga, and In, and

for molecules C2H3, C3H3, C3H4

(allene and propyne), C3H5, C3Hg,

C4H2, C4H4, C4H6, C4H8 (1-butene,

trans-2-butene, and isobutene), CgH2,

CgHg (fiilvene), SiF4, HO2, and six

chlorofluorocarbons (CCIF3, CCI2F2,

CCI3F, CHCIF2, CHCI2E CH2CIF).

The user interface has been significantly

enhanced, and, to accommodate the

extensive additions of data, atomic and

molecular data are now accessible

through separate interfaces.

With the addition of cross section data

for atoms and the molecules, we are

reaching a much wider customer base. The database will benefit those working

in the areas of fusion plasma modeling,

plasma processing of materials, modeling of semiconductor fabrication, and

modeling of combustion chemistry useful to the automotive industry. The

Electron-Impact Cross Sections for

Ionization and Excitation Database can

be accessed on the Web at

http://physics.nist.gov/ionxsec.

This updated database was developed

using two popular Web development

tools: MySQL and PHP. MySQL is a

relational database management system.

PHP, a widely used general-purpose

scripting language, provides interfaces to many different database systems and has

built-in libraries for many common

Web tasks. Both PHP and MySQL have

the strengths of high performance, low

cost, ease of use, efficiency and portability; and they are Open Source solutions.

Using MySQL and PHP, we have creat- ed a Web-based data entry form so that

scientists can now add data to the database. The data retrieval interface (a periodic table and various selection forms) is dynamically generated based on the current contents of the MySQL database.

Thus, when data is entered into the

MySQL database, it is immediately

viewable.

CONTACT; KAREN OLSEN

(301) 975-3286

karen.olsen@nist.30v

53
iWARDS AND HONORS

Service to America

Medal

Deborah S. Jin,

Quantum Physics

Division, was awarded a 2004

Service to America

Medal by Government Executive

Magazine and the

Partnership for PubHc Service. She was

recognized for significant contributions

to the nation in activities related to sci- ence and the environment. The award was for creating "a new form of matter

which could potentially unlock the key

to superconductivity, a phenomenon

with the potential for improving energy

efficiency dramatically across a broad

range of applications."

Academician of the

Pontifical Academy of

Sciences

William D. Phillips,

Atomic Physics

Division, was

appointed a 2004

Academician of the

Pontifical Academy

of Sciences. He was

recognized for his

contributions to science and for his

Christian character, dedication, and

example. The Pontifical Academy of

Sciences was founded in Rome in 1603

with the name Academy of the Lynxes

and led by Galileo Galilei. It is currently

made up of 80 pontifical academicians

named for life by the Pope after having

been proposed by the academicians

themselves.

Davisson-Germer Prize

Paul S. Julienne,

Atomic Physics

Division, received

the 2004 DavissonGermer Prize in Atomic or Surface

Physics from the

American Physical

Society. He was recognized for his

pioneering studies of the theory of

ultracold atomic collisions and its

applications to precision metrology and

quantum gas dynamics. The Prize was

estabhshed in 1965 by AT&T Bell

Laboratories (now Lucent Technologies)

as a means of recognizing outstanding

scientific work in America.

MacArthur Fellowship Frederick Ives Av^ard /Jarus W. Quinn Endowment

Deborah S. Jin, Quantum Physics

Division, was also a 2003 winner of a MacArthur Fellowship, commonly

known as the "genius grant." The

MacArthur Fellows Program awards

unrestricted fellowships to individuals

who have shown extraordinary originality and dedication in their creative

pursuits and a marked capacity for

self-direction.

David J. Wineland, Time and Frequency Division, received the

2004 Frederick Ives Award/Jarus W. Quinn Endowment of the

Optical Society of America, "for development of laser-manipulated

quantum engineering at the single-atom level and application of

these methods to quantum logic systems, atomic frequency standards, and fundamental tests of quantum mechanics." The award is

the highest honor bestowed by the Optical Society of America,

recognizing overall distinction in optics. Dr. Wineland was recognized for his group's world-leading research in quantum state engineering of trapped

ions and repeated breakthroughs in quantum computing, precision frequency standards,

and fiandamental tests of quantum mechanics. These include the first demonstration of

the Schrodinger cat superposition of states in a single ion, the first demonstration of

entanglement of four ions, the first experimental demonstration of all the components

required for a scalable quantum computing architecture, and many other firsts required

for quantum computation.

54
I. I. Rabi Award E. Bright Wilson Award in Spectroscopy

John L Hall,

Quantum Physics

Division, received

the 2004 I. I. Rabi

Award of the

IEEE Society

for Ukrasonics,

Ferroelectricity, and

Frequency Control. Presented at the

2004 IEEE International Frequency

Control Symposium, the award was

for his long-term research and achievements in the area of optical frequency

standards.

Legion d'Honneur Award

John L. Hall, Quantum Physics

Division, was also selected for membership in 2004 in the Legion d'Honneur,

the highest award that the Republic

of France makes to foreigners with

a distinction level of "Chevalier"

("Knight').

Marilyn E. JacOX, Scientist Emeritus, Optical Technology Division,

received the 2003 E. Bright Wilson Award in Spectroscopy from the

American Chemical Society for her outstanding contributions to fundamental spectroscopy of chemical reaction intermediates. She

pioneered matrix isolation spectroscopy—a technique that involves

snaring unstable molecules in an inert chemical framework so they

can be studied—working from theory through novel experimental

design to compilations of data on more than 3,400 neutral and

ionic transient small molecules.

Presidential Rank Award

David J. NTineland, Time and Frequency Division, received a 2004 Presidential Rank Award for Distinguished Senior Executives

and Professionals from the U.S. Office of Personnel Management for

exceptional technical accomplishments, including development of

optical frequency standards, fundamental tests of quantum mechanics, and research on quantum computing.

Presidential Early Career Award

Scott A. Diddams, Time and Frequency Division, received a 2003 Presidential Early Career Award for Scientists and Engineers

(PECASE) for leadership in developing and applying new laser

techniques to measure the frequency of electromagnetic radiation

to unprecedented accuracy and to support development of advanced

standards for time and length. Dr. Diddams was recognized for

his outstanding work on optical frequency synthesis based on

femtosecond laser frequency combs. The PECASE award is the highest honor bestowed by the United States Government on scientists and engineers beginning their independent careers. Sixty awards were given nationally and presented

in a White House ceremony.

55
AWARDS AND HONORS

Arthur S. Flemming Awards

Established in 1948, the Flemming

Awards honor outstanding Federal

employees with no more than fifteen

years ofgovernment service.

Recognized by the President ofthe

United States, agency heads, and

the private sector, about ten winners

are selected each yearfrom all areas

ofthe Federal service.

Deborah S. Jin,

Quantum Physics

Division, received a 2003 Flemming

Award, for breakthrough achievements in coaxing

collections of fermionic atoms into a single quantum state,

analogous to the Bose-Einstein Condensate. In 1999, she produced the first

degenerate Fermi gas of atoms in a

tiny cloud of potassium atoms in a magnetic trap. In 2003 she created the

first Bose-Einstein "Super Molecule," a

Bose-Einstein Condensate of fermionic

molecules.

Muhammad Arif,

Ionizing Radiation

Division, received a 2002 Flemming

Award for his accomplishments in

the development of

two major neutron research facilities and

for major research accomplishments in

the fields of neutron interferometry,

neutron optics, and neutron imaging.

Marc F. Desrosiers,

Ionizing Radiation

Division, received a 2002 Flemming

Award for developing and establishing

alanine/EPR technology as the dosimeter of the highest

metrological quality for measuring the

absorbed dose from ionizing radiation

beams used in radiation processing, and

for extending its use and meeting the

needs of industry through an innovative

e-Certification system he developed for

remote, internet-based, on-demand

calibrations.

Mark D. Stiles,

Electron and

Optical Physics

Division, received a 2002 Flemming

Award for his leadership in the exploration and exploitation of electronic and magnetic properties of nanometer-scale devices. His

research, based on first-principles quantum mechanical calculations, has guided

seminal experiments on electron flow in

transistors, single-electron charging

effects in tunnel junctions, spintronic

devices, and magnetic multilayer structures. In particular, this body of work

has had a significant impact on the

understanding, development, and commercialization of "giant magnetoresistive" devices, a breakthrough technology

for the data storage industry.

Charles S. Tarrio,

Electron and

Optical Physics

Division, received a 2003 Flemming

Award for pioneering contributions to

the measurement of

extreme ultraviolet (EUV) light, and its

applications in semiconductor lithography, astronomy, and physical sciences.

Dr. Tarrio established an EUV metrology facility at the NIST SURF synchrotron light source that has become the

leading provider of measurement and

characterization services to the international EUV optics community. During

a decade of service this facility has

performed well over 1 000 tests for the

user community, all on components that

have been fabricated with tolerances at

the cutting edge of measurement science. These include EUV telescopes that

have been flown in satellite missions,

optics for EUV semiconductor lithography systems, mirrors for x-ray lasers, and

a variety of new devices for the generation, control and measurement of EUV

light. Since EUV light has a wavelength

of 10 nanometers, its optics must be

formed to an accuracy of 1 nanometer,

the size of 10 atoms. His focus on accurate metrology has led Dr. Tarrio to make a number of discoveries that have

advanced the nanometer-scale technology of EUV optics, ranging from basic

optical properties of materials to improved methods of nanofabrication.

56
r

AWARDS AND HONORS

Fellowship of the American Association for

the Advancement of Science

Katharine B. Gebbie, Director of the Physics Laboratory, was

elected a 2004 Fellow of the American Association for the

Advancement of Science "for her inspired directorship of the

NIST Physics Laboratory, which is a world leader in the fields of atom cooling and trapping, nanotechnology, quantum

metrology, and quantum computation."

Fellowship of the American Physical Society

Mark D. Stiles,

Electron and

Optical Physics

Division, was elect- ed a 2004 Fellow of

the American

Physical Society,

"for his creative and

skillfiil use of first principles calculations

and phenomenological models that have

substantially contributed to our understanding of the physics of magnetic heterostructures."

Deborah S. Jin,

Quantum Physics

Division, was elected a 2003 Fellow of

the American

Physical Society, for

her innovative realization and exploration of a novel quantum system, the

degenerate Fermi atomic gas.

Joseph A.

StroSCio, Electron

and Optical Physics

Division, was elect- ed a 2002 Fellow of

the American

Physical Society,

"for advancing our fundamental knowledge of semiconductor and metal surfaces and the innovative development, application, and dis- semination of advanced methods of

scanning tunneling microscopy and

spectroscopy."

Washington Academy of

Sciences Physical Science

Award

William R. Ott,

Deputy Director of

the Physics Laboratory, received the

2004 Physical

Sciences Award from

the Washington

Academy of Sciences

and was elected a Fellow for his leadership

of the NIST Physics Laboratory in supporting industry, government, and the

scientific community with measurement

research and services in electronic, optical,

and ionizing radiation technologies.

Charles W. Clark,

Electron and Optical

Physics Division,

received the 2003

Physical Sciences

Award of the

Washington Academy of Sciences,

and was elected a Fellow for his contributions to the physics of quantum manybody systems.

Fellowship of the Optical Society of America

Jabez J. McClelland, Electron

and Optical Physics

Division, was elected

a 2004 Fellow of the

Optical Society of

America, for contributions to atom

optics, including the fabrication of

stable structures by direct-write atomic

lithography.

Paul D. Lett, Atomic

Physics Division, was

elected a 2003 Fellow

of the Optical Society

of America in recognition of his development of photoassociative spectroscopy as a tool for studying

interactions between ultracold atoms.

57
AWARDS AND HONORS

Distinguished Visiting Fellow Award

John D. Gillaspy, Atomic Physics Division, received the 2004

Distinguished Visiting Fellow Award at the new International

Research Centre for Experimental Physics at the Queen's University of Belfast. He was recognized for his expertise in the physics

and applications of highly charged ions, the focus of research in

the "Ion Hall" that comprises most of one floor of the new Centre.

The competitive award was designed to bring in internationally

recognized physicists to enhance interdisciplinary research activity.

Bourke Lectureship Award

Paul D. Lett, Atomic Physics Division, received the 2004 Bourke

Lectureship Award. He was recognized for his distinguished work

on cooling and trapping of atoms, on ultralow energy atomic collisions and on photoassisted association at ultralow temperatures.

Dr. Lett was selected by the Faraday Division of the Royal Society

of Chemistry. The award was presented by the Imperial College,

United Kingdom.

David J. Ncsbitt, Quantum Physics Division, was awarded the

2002 Bourke Lectureship of the Faraday Division of the Royal

Society of Chemistry. The Faraday Society instituted the lectureship in 1954 as a means to bring distinguished scientists from

overseas to lecture in Britain.

IEEE Ferroelectrics and Frequency Control Society

Distinguished Lecturer

Steven JeffertS, Time and Frequency Division, was selected as

the IEEE Ferroelectrics and Frequency Control Society Distinguished Lecturer for 2003-2004. Dr. Jefferts was selected because

of his international prominence in the field of frequency standards

as the leader of the NIST-Fl primary frequency standard team. Through the Distinguished Lecturer program. Dr. Jefferts gave

many lectures on "Atomic Clocks—Past, Present, and Future"

in Europe, Asia, and the United States.

Tom L. Popejoy

Dissertation Prize

Joshua C. Bienfans,

Electron and Optical

Physics Division,

received the 2003

Tom L. Popejoy

i '^P^. Dissertation Prize of

«3 rni^r.i: - the University of New

Mexico. Dr. Bienfang was recognized for his 200 1 physics

Ph.D. dissertation, Laser Frequency

Stabilization and Nonlinear Conversion.

The award citation describes this

dissertation as "a rare combination of

sophisticated experiments and theory."

Sigma Xi (NIST Chapter)

Young Scientist Award

James Porto,

Atomic Physics

Division, received the

2004 Young Scientist

Award from the

NIST Chapter of

Sigma Xi. He was

recognized for excellence in quantum engineering research

using ion and atom traps.

W. J. Youden Award

Kenneth G. W. Inn,

Ionizing Radiation

Division, received the

2003 W. J. Youden

Award in Interlaboratory Testing for

recognition of the

paper. An Alternative

Statistical Approach for Interlaboratory

Comparison Data Evaluation, published

in the Journal of Radioanalytical and

Nuclear Chemistry, 248, 163-173

(2001).

58
AWARDS AND HONORS

James F. Gibbons Award

David DeWitt,

Faculty Appointment, Optical

Technology

Division, received

the 2004 James F. Gibbons Award

from the IEEE,

for pioneering work in the field of

advanced thermal processing of semiconductor materials.

Best Paper Award in

Applied Metrology

George P. Eppeldauer,

Optical Technology

Division, received

the Best Paper

Award in the

Applied Metrology

Category of the

2004 NCSL International Workshop

and Symposium. The award was given

for Irmdiance Responsivity Scale

Realization between 1 ]im and 2.5pim, a

paper describing the extension of the

NIST reference detector responsivity

scale from the visible to the infrared

range. The paper also describes a newly

developed extended-InGaAs radiometer

that can propagate the new scale to calibrate infrared devices and systems with

low measurement uncertainty.

Gold Medal (DoC)

The Gold Medal is the highest honor award conferred upon an employee by

the Department of Commerce, for "distinguishedperformance characterized by extraordinary, notable, or prestigious contributions that impact the

mission ofthe Department ofCommerce and/or operating unit and which

reflectfavorably on the Department.

"

Charles W. Clark, Electron and Optical Physics Division, received

a 2004 Gold Medal, "for leadership in establishing NIST as the

world's foremost center of excellence in quantum computing and

quantum information science and engineering."

Subsequent to major breakthroughs at NIST in quantum physics in

1995, Dr. Clark established a Quantum Information/Bose-Einstein

Condensation center of excellence where scientists from around the

world could work together on the latest ideas in quantum engineering. QIBEC has been

immensely successful, due primarily to Dr. Clark's dynamic leadership. He created a forum for new developments in quantum communication, cryptography, and information processing, areas where NIST is now preeminent, and has promoted innovation and

excellence through his leadership and personal technical excellence.

Steven Jefferts, Thomas Heavner,

and Elizabeth Donley, Time and

Frequency Division, received a 2004

Gold Medal for designing, constructing, operating, and continually improving the world's most accurate atomic

clock, the NIST-Fl laser-cooled cesium

fountain primary frequency standard.

NIST-Fl is the U.S. national standard

for frequency and the SI second, with a fractional frequency uncertainty of about

6 xlO"'*" as of December, 2004. NIST-Fl is the calibration source for the NIST time

scale, which underpins NIST's most heavily used services, including the Internet Time

Service and NIST radio broadcasts.

Albert C. Parr, Optical Technology Division, received a 2003 Gold

Medal, "for strategic leadership in building major technical pro- grams responsive to measurement needs of the Nation. " These

include the needs of the military for effective night vision sensors and missile detection systems and the needs of remote sensing net- works for high accuracy optical radiation measurements to monitor

global climate change. In addition, he addressed the needs of the

microelectronics industry for noncontact optical probes of manufacturing processes and the needs of major manufacturing sectors for sophisticated color

and appearance standards to ensure quality of consumer products.

59
AWARDS AND HONORS

Silver Meda! (DoC)

The Silver Metal is the second highest honor awarded by the Department of Commerce, for "exceptionalperformance

characterized by noteworthy or superlative contributions that have a direct and lasting impact.

"

B. Carol Johnson and Steven W.

Brown, Optical Technology Division,

received a 2004 Silver Medal, "for their

innovative approach to optical sensor cali

bration which resulted in a 6 percent

decrease in the satellite-derived ocean

chlorophyll a level, a critical measure of

carbon dioxide intake by the oceans

Charles S. Tarrlo and Steven Grantham,

Electron and Optical Physics Division,

received a 2004 Silver Medal, "for establishing a measurement science program that

has brought NIST to a position of world

leadership in the emerging technology of

extreme ultraviolet optics." Drs. Tarrio and

Grantham combined basic measurement

science with high responsiveness to customer needs, in an area of rapid technological

change and key economic importance. They built a major national facility for the optical characterization of extreme ultraviolet (EUV) imaging systems based at the NIST

Synchrotron Ultraviolet Research Facility (SURF), and established NIST as the clear

international leader in EUV metrology. In light of their work, NIST has led the effort

to standardize EUV optical measurements worldwide.

Michael P. Unterweger Jr. and Letlcia

PIblda, Ionizing Radiation Division,

received a 2004 Silver Medal for leadership

in the development and implementation of

radiation detector standards for homeland

security. These standards address the per- formance of radiological detection equipment to be used by personnel involved in

border control, customs, coast guard, and postal services requiring the detection, monitoring, and interdiction of illicit radiological material entering and transported through

the country. These standards will provide crucial support for first responders needing

reliable measurements of radioactive material in homeland security situations.

Carl J. Williams,

Atomic Physics

Division, received a 2003 Silver Medal,

for leadership of the

NIST Quantum

Information

Program. The

Program combines NIST laboratory

research efforts in Boulder, CO, and

Gaithersburg, MD, in a coordinated

effort towards early implementation of

quantum information processing technology. It has grown into a multidisciplinary effort that is internationally

recognized for its accomplishments,

and is a primary provider of quantum

information technology and expertise to

the defense, intelligence, and scientific communities.

60
Bronze Medal (NIST)

The Bronze Medal is the highest honorary recognition available for Institute presentation. The award recognizes

work that has resulted in more effective and efficient management systems, as well as the demonstration ofunusual

initiative or creative ability in the development and improvement ofmethods andprocedures. It is also given for

significant contributions affecting major programs, scientific accomplishment within the Institute, and superior

performance ofassigned tasks for at leastfive consecutive years.

Michael G. Mitch, Ionizing Radiation Division, received a 2004

Bronze Medal for providing measurement services to enable the

consistent, safe, and efficacious use of brachytherapy radiation

sources, such as prostate seeds. The implantation of tiny radioactive

seeds in the prostate to kill diseased tissue is being increasingly used

for cancer therapy. This has stimulated a ten-fold growth in manufacturers of such seeds. Since 1999, when NIST introduced a primary standard for measuring seed strength with high accuracy

regardless of design, Dr. Mitch worked with manufacturers, secondary calibration labs,

and clinics to disseminate this unique capability. His services are important for ensuring

stability and consistency of manufacturing processes, necessary for FDA and NRC

approval and the eventual use of the seeds in patients. He works closely with a national

network of accredited calibration labs in transferring seed calibrations and providing

proficiency testing.

Maria E. Nadal and Edward A. Early,

Optical Technology Division, received a 2004

Bronze Medal for developing a state-of-the-art instrument to meet industry's needs for improved color measurements and standards.

Incorrect color measurements waste 2 % to

3 % of manufacturing costs and affect virtually

every commercial product and all tiers of the

supply chain due to the wide use of plastics, paints, coatings, inks, pigments, and dyes

by manufacturers. The team also developed the statistical analysis tools to help industry

determine their color measurement uncertainties. By allowing U.S. products to meet

stringent color specifications, independent of manufacturing locale, these new NIST

capabilities and measurement services have strengthened U.S. industrial competitiveness.

Joseph P. Rice,

Optical Technology

Division, received a 2004 Bronze Medal

for developing an

innovative radiometer to link infrared

measurements from

U.S. satellites to NIST optical radiation

scales. Satellite sensors provide information about land and sea-surface temperatures, cloud heights, humidity profiles,

concentration and distributions of

atmospheric molecules and pollutants,

and forest fires.

61
AWARDS AND HONORS

Bronze Medal (NIST) (continued)

Robert E. Vest, Electron and Optical Physics Division, received a 2004 Bronze Medal for providing high quality calibration services

for far ultraviolet detectors and working with customers to improve

the measurement technology. Photodetectors calibrated on his beamline at the NIST Synchrotron Ultraviolet Radiation Facility

are found in virtually every major UV radiation measurement labo-

^1 /.'/'^ ratory in the world. With his collaborators, he has devised several new detectors for applications of growing industrial importance.

such as 193 nm and 157 nm lithography.

Alan H. Band, Electron and Optical Physics Division, received a 2003 Bronze Medal for his outstanding success designing and fabricating electronic instrumentation. Mr. Band designed and supervised the construction of the Electron Physics Groups scanning

tunneling microscope, autonomous atom assembler, scanning electron microscope with polarization analysis, and single atom-ondemand source. Mr. Band has frequently been sought out for collaborative projects with other Laboratories within NIST. Because

of his skill, industry, and creativity, he was instrumental in the success of several highly

important NIST programs. In addition, the Smithsonian currently features a display he

designed for their "Science in American Life" exhibit.

Angela R. Hight Walker, Optical Technology Division, received

a 2003 Bronze Medal, for leadership in developing stronger

programmatic ties between NIST and NIH and in increasing

the opportunities for scientific collaboration and institutional

cooperation with NIH.

Lawrence T. Hudson, Ionizing Radiation Division, received a 2003 Bronze Medal "for outstanding response to a national emer- gency by coordinating and implementing a protocol for the decontamination of the mail by irradiation." His design and validation

of an x-ray imaging process permitted parcels that had been quarantined to be sanitized and released after the widely publicized

anthrax terror attacks using the U.S. mail system.

Samuel Wesley Stratton

Award (NIST)

The Samuel Wesley Stratton Award

is grantedfor outstanding scientific

or engineering achievements in

support ofNIST objectives.

Paul S. Julienne,

Atomic Physics

Division, received

the 2004 Stratton t

' Award for worldleading theoretical

physics research

^ ^^^H in ultracold

collisions fondamental to the laser cooling of atoms and to Bose-Einstein

condensation.

David J. Wineland, Time

and Frequency

Division, received

the 2003 Stratton Award for pioneering research in quantum engineering for quantum computing, precision

frequency standards, and fundamental

tests of quantum mechanics. Dr. Wineland was recognized for his Ion

Storage Groups world-leading research

in quantum state engineering of trapped

ions with repeated breakthroughs in quantum computing, precision frequency standards, and fondamental tests of

quantum mechanics.

62
PHYSICS LABORATORY RESOURCES

PHYSICS LABORATORY RESOURCES 2000 - 2004

($ MILLIONS)

Key to Table

Abbreviations

STRS Congressionally appropriated

funds for NIST s Scientific and

Technical Research and Services

ATP Intramural research firnds provided to support the goals of the

NIST Advanced Technology

Program

OA Funds provided by other

agencies in support of needed

research and measurement

services

Other Other sources of funding,

including calibration fees

STRS

ATP

OA

Other

TOTAL

2000

34.8

1.8

10.6

4.4

51.6

2001

37.1

2.1

11,9

4.5

55.6

2002

39.9

2.9

13.6

5.0

61.4

2003

43.1

2.7

14.0

5.2

65,0

2004

40,3

0.6

20.8

5.2

66,9

Federal Agencies Supporting

Physics Laboratory Research

- Department of Commerce

- Department of Defense - Department of Energy - Department of Health and

Human Services - Department of Homeland Security - Department of Justice - Environmental Protection Agency - National Aeronautics and Space

Administration - National Science Foundation

Representative Private Sector Collaborators

American Association of Physicists

in Medicine

American National Standards Institute

American Physical Society

American Society for Testing

and Materials

Commission Internationale de

I'Eclairage

Council for Optical Radiation

Measurements

Council on Ionizing Radiation

Measurements and Standards

Electric Power Research Institute

EUV LLC

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 — Optoelectronics Industry Development

Association — International SEMATECH

— SAE International — SPIE—The International Society

for Optical Engineering

63
ORGANIZATIONAL CHART

PHYSICS LABORATORY

Katharine Gebbie, Director • William Ott, Deputy Director

Electron and Optical Physics Division mm

llllllllll^

Charles Clark, ^^^^^^^^^^J

Optical Technology Division

Albert Parr, Chief

^^^^^B Ionizing Radiation Division

^^^^^K Lisa Karam, Acting Chief

Biil^' Time and Frequency Division

, _ ^ ^

, Thomas O'Brian, Chief

Quantum Physics Division

Steven Cundiff, Chief

64
EDITORS;

Jonathan E. Hardis and William R. Ott

Physics Laboratory, National Institute

of Standards and Technolosy

U.S. Department of Commerce

Donald L. Evans, Secretar/

Technolosy Administration

Phillip J. Bond, Under Secretar/ for Technology

National Institute of Standards and Technolosy

Hratch G. Semerjian, Acting Director

NIST SP 1033

February 2005

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