SUPPORTING U.S. INDUSTRY,

GOVERNMENT, AND THE SCIENTIFIC

COMMUNITY BY PROVIDING MEASUREMENT

SERVICES AND RESEARCH FOR ELECTRONIC,

OPTICAL, AND RADIATION TECHNOLOGY

Nisr

National Institute of Standards and Technology

Technology Administration

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

Director's Message 2

Electron and Optical Physics Division 4

Atomic Physics Division 12

Optical Technology Division 20

Ionizing Radiation Division 28

Time and Frequency Division 36

Quantum Physics Division 44

Office of Electronic Commerce in 52

Scientific and Engineering Data

Honors and Awards 54

Physics Laboratory Resources 63

Organizational Chart 64
PL VISION

Preeminent performance in measurement

science, technology, and services.

PL MISSION

The mission of the NIST Physics Laboratory

is to support U.S. industry, 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

fundamental quantum processes.

PL GOALS

Physics Laboratory develops goals within

its mission and focus areas. These include

health care quality assurance, nanoscale

measurements and data, and measure- ments and standards that support homeland security. In addition to these overarching 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 explore their

applications.

Optical Technology Division: to provide

the foundation of optical radiation measure- ments for our Nation.

Ionizing Radiation Division: to provide

the foundation of ionizing radiation

measurements for our Nation

Time and Frequency Division: to

provide the foundation of frequency

measurements and civil timekeeping for our Nation.

Quantum Physics Division: to provide

fundamental understandings of nano-,

bio-, and quantum optical systems in partnership with the University of Colorado

at JILA.

Office of Electronics Commerce in

Scientific and Engineering Data: to coordinate and facilitate the electronic dis- semination of information via the Internet.

PL RESOURCES

199 full-time staff (147 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

$61 million annual budget

Unique facilities, including:

-Controlled Background

Radiometric Facility - Electron Beam Ion Trap (EBIT) - Electron Paramagnetic

Resonance Facility - EUV Optics Fabrication and

Characterization Facility - High-Resolution UV and Optical

Spectroscopy Facility - Low-Background Infrared Radiation Facility - Magnetic Microstructure

Measurement Facility - Medical-Industrial Radiation Facility (MIRF) - Nanoscale Physics Laboratory - Neutron Interferometer and Optics

Facility (NIOF) - NIST Beowulf System - Radiopharmaceutical Standardization

Laboratory

- Spectral Irradiance and Radiance

Responsivity Calibrations Using

Uniform Sources (SIRCUS) Facility - Synchrotron Ultraviolet Radiation

Facility (SURF HI) - W.M. Keck Optical Measurement

Laboratory

Standard time dissemination services:

- Radio stations WWV, VWWH,

and WWVB

-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 electrons - High-precision time - Neutron sources and neutron dosimetry - Optical wavelength - Oscillator frequency - Phase and amplitude noise - Photodiode spectral responsivity - Photometry (e.g., luminous intensity,

luminous flux, illuminance) - Radiance temperature - Radioactivity sources - Spectral radiance and irradiance - Spectral transmittance and reflectance

PL WEB SITE

http://physics.nist. gov/

1
DIRECTOR'S MESSAGE

Wehope this report conveys the excitement and the relevance of the programs within the NIST

Physics Laboratory. First and foremost, we support U.S. industry by providing measurement

services and research for optical, electronic, and radiation technologies. Our great strength—and

what distinguishes us from an academic or industrial laboratory—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, measurements,

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.

For 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 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

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 non-contact thermometry

(the kelvin, especially above 1200 K).

We provide the basis for such SI dehved

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.

2
Our partners are many and our outreach

is extensive. For optical radiation measurennents, 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 Ionization

Radiation Measurements and Standards

(CIRMS) helps to advance and disseminate

the physical standards needed for the

safe and effective application of ionization

radiation, including vacuum ultraviolet,

X ray, gamma ray and energetic particle

such as electron, proton, and neutron. 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 staff

serve with distinction in standards-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. And twice since

1997, Laboratory staff members 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 in 2002.

Our talent is focused on meeting today's

challenges—in 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-frequency

signals as diagnostic tools.

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, since 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 web site, http://physics.nist.gov/,

and we invite your inquiries and interest in

measurement services and collaborations.

Katharine Gebbie

Director, Physics Laboratory

3
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-iritensive industries.

The first strategic focus is to develop techniques

for fabricating nanostructures and measuring their

electronic and magnetic properties.

Nanoscale Electronics

and Magnetics

INTENDED OUTCOME AND

BACKGROUND

The intended outcome of this work is

the continuous improvement of techniques for fabncating 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 program

are scanning electron microscopy with

polarization analysis (SEMPA) and scanning tunneling microscopy (STM). The

Electron Physics Group in the Division has

been a leading innovator in both of these

techniques, which are outgrowths of

work begun at NIST in the 1970s.

SEMPA enables us to use conventional

scanning electron microscopy (SEM) to

image nanometer-scale 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 surface-sensitive

technique, and so is especially well suited

for in situ studies of thin-film and surface

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 microscopic scale, and have also addressed

near-term measurement issues faced by

the magnetic data-storage industry.

Our STM program is focused on understanding the mechanisms of growth of

nanostructures on surfaces and determining their electronic properties. In recent

years the STM program has been particularly concerned with the magnetic multilayer materials that have been investigated

by SEMPA. The complementarity of SEMPA

and STM measurements has 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. The laboratory was designed with the goal of measuring quantum-electronic structures with

atomic-scale imaging resolution and high

electron-energy resolution. Samples can

be grown in situ and probed with magnetic fields of up to 10 T at temperatures

down to 2.5 K.

4
ACCOMPLISHMENTS

Nanometer-Scale

Measurements of the

Vortex Lattice in a Type-ll

Superconductor

We have made the first real-space measurements of the hexagonal-to-square

symmetry transition in the vortex lattice of

VgSi, a type-ll superconductor. The mixed

state in a type-ll superconductor is characterized by the properties of the vortex or

flux lattice that forms in the presence of

an applied magnetic field. Vortices are

formed at points where the magnetic field

penetrates the superconductor in a flux

tube through the sample. The flux penetrates the superconductor in quantized

units of the flux quantum (<I>o= h/2e),

with the region near the core of the

vortex acting as a normal metal. As the

density of vortices in the material increases,

a vortex lattice is formed by the interactions

between the flux tubes or vortices.

Many of the important applications of

superconductors rely on the formation

and stabilization of the vortex lattice at

= h/2e

Figure 1 . Vortex flux lattice in VjSi observed in STM Fermi-level conductance image at 1-1=3 T and T=2.3 K. The peaks indicate the location

of vortices with a single flux quantum of

magnetic flux.

high values of applied field. For example,

the optimization of vortex pinning in

high-Tc materials controls flux creep and

is responsible for the high critical currents

needed for the operation of superconducting magnets. Probing the underlying

physics of the vortex lattice is not only of

technological importance, it is also the

key to understanding more complex

interactions, such as the coexistence

of superconductivity and magnetism.

Real-space measurements of vortex lattices are difficult because the length scale

of the vortex unit cell is in the nanometer

range for field strengths on the order of

1 T. Such measurements are now possible

using cryogenic scanning tunneling

microscopy, which probes the electronic

structure of the superconductor on the

atomic scale.

Measurements of the symmetry transition

in VjSi were made by recording spatial

maps of the local density of states (LDOS)

of the superconductor as a function of

magnetic field, using the low-temperature

scanning tunneling microscope of the

Nanoscale Physics Laboratory in the

Electron Physics Group. At the location of

the vortex, the superconductor is a normal

metal and has a much higher density of

states for energies inside the superconducting gap. Thus, spatial maps of the

LDOS show a bright spot at the location

of the vortex.

Figure 2. (a-d) STM Fermi-level conductance

images of the vortex lattice of VgSi as a function

of applied magnetic field at 2.3 K. (e-h)

Corresponding auto-correlation images showing

the unit cell of the vortex lattice undergoing

the hexagonal-to-square symmetry transition.

5
Measuring the vortex lattice as a function

of magnetic field shows that vortex-vortex

interactions are innportant in determining

the symmetry of the vortex lattice.

Moreover, the measurements reveal that

symmetries in the electronic structure of

the superconductor play an important

role, as they directly link the symmetry

of the vortex lattice to the underlying

crystal structure.

CONTACT: Dr. Joseph A. Stroscio

(301) 975-3716

joseph.stroscio@nist.gov

Magnetic Nanostructures

in Patterned

Ferromagnetic Rings

Small, patterned, magnetic, thin-film

structures are a critical part of emerging

magneto-electronic technologies, which

range from non-volatile magnetic randomaccess memories to magnetic biosensor

arrays. To be useful in devices, the magnetic structure of these rings must assume

only a few well-defined magnetic states, and the switching between states must

be reproducible.

In collaboration with the Naval Research

Lab and the University of Cambridge

Thin-Film Magnetism Group, we have used

the NIST Scanning Electron Microscopy

with Polarization Analysis (SEMPA) facility

to non-intrusively image the magnetic

nanostructure of a promising subclass of

these structures: microscopic magnetic

rings. The SEMPA images provided a

first direct look at these magnetic states.

o 1 [jnn

Magnetization

Direction

Figure 3. SEMPA image of a magnetic Co ring (center) along with a micromagnetic simulation (right).

By comparing different sized thin-film

elements grown under various conditions,

the SEMPA images revealed that the

interplay between shape and crystalline

anisotropy can lead to unexpected magnetic configurations. In particular, undesirable magnetic vortices can be induced in

thick-walled rings during switching. The

SEMPA images were also used as a quantitative test of micromagnetic models

that, in turn, can explore regions of the

switching behavior not accessible to

static SEMPA measurements.

CONTACT: Dr. John Unguris

(301) 975-3712

john.unguris@nist.gov

netizations of the layers between parallel

and antiparallel. In other configurations,

it appears that the magnetization of one

layer rapidly precesses around that of the

other layer.

These effects, which were observed starting in 1999, are being studied for two

device applications. If the size of the current necessary to reverse magnetic bits

can be reduced sufficiently, spin-transfer

torques could provide a way to switch

bits in magnetic random-access memory

(MRAM). Alternatively, if the interpretation of recent experiments as precession

is correct, it should be possible to make

controllable-frequency oscillators.

Switching Nanomagnets

A current passing through two ferromagnets separated by a non-magnetic spacer

layer exerts a torque on each magnetization whenever the two magnetization

directions are not parallel. In the appropriate configuration, a large enough current

passing through such a multilayer can

switch the relative alignment of the magCu Co Cu Co Cu

Figure 4. Electron spin scattering from

a ferromagnetic interface. The change

in spin due to scattering rotates the

magnetization.

6
We have developed quantitative models

for spin-transfer torques to help enable

the developnnent of devices based on this

effect. These models require three types

of calculations. We have carried out quantum-mechanical calculations to determine

the fate of an electron that scatters from

an interface with a ferromagnet. These

calculations show that the transverse component of the incident spin current

is absorbed close to the interface.

We use this result as a boundary condition

in the second type of calculation, semiclassical transport. These calculations

determine the polarization, both magnitude and direction, of the current

throughout the structure. With the input

from the first-principles calculations, our

semiclassical calculations reproduce both

the transport properties of the structures

and the current-induced torques.

Analyzing the calculations in detail highlights the important physical processes,

which are difficult to access experimentally.

The calculated torques can be used as

input to the third type of calculation,

classical simulations of the magnetization

dynamics.

CONTACT: Dr. Mark D. Stiles

(301) 975-3745

mark.stiies@nist.gov

Linking the Micro and Nano

Worlds with Nanolines

As technologies ranging from electronics

and data storage to biotechnology

become more and more miniaturized,

there is an increasing need for ways

to make measurements that bridge

the domains of the micrometer and

the nanometer

Figure 5. Beating of nanolines: the superposition of two nanoscale patterns with slightly

different periodicities results in an optically

visible beating on the microscale.

We have collaborated with scientists from

the University of Nijmegen to make an

artifact that facilitates this connection. It

relies on a technology first demonstrated

in the Electron Physics Group in 1993,

called laser-focused atomic deposition. In

its original form, an optical standing wave

focused chromium atoms onto a surface,

creating an array of lines with a highly

precise spacing of 212.78 nm. In the new

process, two arrays of lines with slightly

different spacing are superimposed,

creating a beating, or Moire, pattern with

periodicity of 44.46 pm. When viewed

through crossed polarizers, this pattern is

clearly visible with an optical microscope.

The result of this process is that nanometer-scale and micrometer-scale patterns

are created on a single substrate in coherent registration with each other Ongoing

investigations indicate that because of

the resonant nature of the laser-focused

atomic-deposition process, the dimensions

of the patterns may be accurately traced

to an atomic frequency, so that the

patterns can be used as absolute length

standards on the nano- and micro-scale.

CONTACT: Dr. Jabez J. McClelland

(301)975-3721

jabez.mcdelland@nist.gov

Electron Beam Induced

Magnetic Switching

Understanding and controlling the magnetic properties of ferromagnetic thin

films grown on semiconductor substrates

is a chtical element in developing hybrid

magnetic/semiconductor magnetoelectronic devices. We use the exquisite

surface sensitivity provided by SEMPA

to systematically explore the properties

of various ferromagnet/semiconductor

combinations. As part of this work, we

discovered that electron beams can be

used to induce changes in the magnetization direction in ferromagnetic thin films.

Figure 6. A series of SEMPA images from

Fe/GaAsd 10) showing the electron-beaminduced magnetization reonentation.

7
When Fe films are grown epitaxially on

the (110) crystal surface of GaAs, the

magnetization can be trapped in a

metastable state, oriented along the

[-1 10] direction. Irradiating the sample

with an electron beam causes the

magnetization to locally rotate by 90°

into the stable [100] direction.

In addition to providing information

regarding domain-wall dynamics in

Fe/GaAs, this phenomenon may also

provide a means of locally writing magnetic information or patterns in Fe films

with electron-beam precision. Work is underway to understand the electronbeam/sample interaction that drives

the reorientation, and to investigate its

potential for electron-beam writing of

magnetic information.

CONTACT: Dr. John Unguris

(301) 975-3712

john.unguris@nist.gov

Figure 7. NIST Synchrotron Ultraviolet

Radiation Facility (SURF III) and Beamlines

1-5, with principal users and staff.

The second strategic focus is the development of

metrology for extreme-ultraviolet (EUV) optics, the

maintenance of national primary standards for radiometry

in the EUV and adjoining spectral regions, and the

operation of national user facilities for EUV science

and applications.

Extreme Ultraviolet

Radiation Metrology

INTENDED OUTCOME AND

BACKGROUND

The intended outcomes of this program

are: maintenance and continuous

improvement of the national primary

measurement standards for extremeultraviolet radiation (EUV: wavelengths

between 2 nm and 200 nm, from soft

X rays to vacuum ultraviolet), development

of techniques for fabricating and characterizing EUV optical systems, and the

development of a synchrotron-based,

national primary standard for sourcebased optical radiometry.

The Division has longstanding responsibility

for the primary national radiometric standards in the EUV region. EUV radiation

is an important tool for determining the

electronic structure of materials, diagnosing plasmas, measuring dynamics of the

upper atmosphere, and probing the

structure and dynamics of astrophysical

objects. One of the key candidates for

next-generation semiconductor lithography is an EUV light source, since its short

wavelength (13 nm vs. 193 nm for present ultraviolet production lithography)

enables diffraction-limited imaging of

features with smaller critical dimensions.

We are working actively with the semiconductor industry to develop "optical

bench" capabilities for characterizing

EUV imaging systems.

The Division's key tool for EUV optical

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, since it does

not produce the hard x-ray radiation of

higher-energy sources and 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.

8
ACCOMPLISHMENTS

Metrology for ExtremeUltraviolet Lithography

New semiconductor industry requirements

for highly accurate EUV reflectivity measurements have provided the impetus for

an international comparison of results

of measurements at four different EUV

facilities: the Advanced Light Source at

Lawrence Berkeley National Laboratory

(CXRO), the PTB instrument at the BESSY

storage ring in Berlin, the ASET instrument

in Japan, and SURF III at NISI

Each lab provided at least one multilayer

mirror, which they measured before and

after the entire set had been measured at

the other facilities. (This was to account

for the aging of the mirrors.) For each

mirror, the object was to determine the

wavelength of peak reflectivity, and the

reflectivity at that wavelength.

Figure 9. White light from SURF III (right) is

reflected by diffraction grating (foreground),

to display spectrum on screen.

Figure 8 shows the results for one sample

that is typical of the set. From these

results we are confident that the NISTquoted uncertainty of 0.3 % is a reliable

estimate. This uncertainty represents a

factor-of-ten improvement over earlier

instrument performance, before a comprehensive set of improvements were made in response to more stringent

industry demands.

0.625

0.624

0.623

0.622

0.621

0.620

0

PT i

NI5T

j

ASET

13,480 13.485 13.490 13.495 13.500 13,505 13.510 Wavelength of Peak Reflectivity [nm]

Figure 8. Results of the international comparison of reflectivity and wavelength of maximum

reflectivity of a test EUV multilayer mirror, from

the Center for X-Ray Optics, (Berkeley CA),

the Physikalisch-Technische Bundesanstalt

(Berlin), the Association of Super-Advanced

Electronics Technologies (Japan), and NISI

CONTACT: Dr. Charles S. Tarrio

(301) 975-3737

charles.tarrio@nist.gov

Absolute Radiometry

at SURF III

The NIST Synchrotron Ultraviolet Radiation

Facility (SURF III) serves as the Nation's

primary standard for absolute sourcebased optical radiometry from the visible

through the extreme-ultraviolet (EUV)

spectral regions. It supports a variety of

scientific and measurement missions,

primarily in the EUV.

One of SURF'S main customers is NASA,

which calibrates virtually all its spaceborne

EUV spectrometers at the spectrometer

calibration facility on SURF Beamline 2.

Recent calibrations include instruments

flown on the Thermosphere Ionosphere

Mesosphere Energetics and Dynamics

(TIMED) mission, the EOS SORCE SOLSTICE

A and B missions (Earth Obsenying System,

Solar Radiation Climate Experiment, Solar

Stellar Irradiance Comparison Experiment),

and the SETI/UCSB (VUV Stimulated

Mid-IR Expenment) mission.

We have completed an upgrade of the

accelerator to improve the radiometric

performance, both in accuracy and spectral range. Absolute flux uncertainties are

better than 1 % from 2 nm to beyond

400 nm. The storage ring now operates

typically at an electron energy of 380

MeV, rather than the 284 MeV energy

of SURF II. This results in a significant

increase in the flux at soft x-ray wavelengths. Testing of the magnet system

has shown the capability of operating

from 73 MeV to 417 MeV

Figure 10. The new white-light radiometry

endstation on Beamline 3.

9
SURF III Status Display

Beam Current 74.15 nlA

Electron Energy

380.0 MeV

Lifetime RK Voltage 12.76 h 27,33 kV

Orbital radii s 337.0773 mm

Ring Vacuum

5.43E-10hPa FWHM X FWHM Y

4.67 mm 1.00 mn, , '2:00 14:00 16:00 17:53

PeaklA/avelength

^'"'^

6.40 nm Last updated: 09-Aug-2002 17:53:33 . .- .Ui Comment: Normal operation ^mjg^jm

The third strategic focus is metrology for coherent

matter-wave and quantum information processing

devices.

Figure 1 1. SURF operations at high current

for EUV optics characterization.

Figure 12. SURF at low current for EUV

spectrometer calibration.

SURF can be run under a wide variety

of operating conditions according to the

needs of different users. Figures 1 1 and

12 show the quite different conditions

required for EUV optics metrology and

satellite spectronneter calibration.

CONTACT: Dr Mitchell L. Furst (301)975-6378

mitcheli.furst@nist.gov

Coherent Matter-Wave

and Quantum

Information Processing

Metrology

INTENDED OUTCOME AND

BACKGROUND

The intended outcome of this program

is to provide measurements and data

needed for 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 expehmental. The theoretical program is focused on quantitative modeling of degenerate

quantum gases, with particular attention

to the dynamics of Bose-Einstein condensates subject to external forces, e.g.,

manipulation of condensates confined in

an optical lattice. This program is an out- growth of extensive collaborations with

experimental groups at NIST, JILA, and

elsewhere, begun in the mid-1990s.

The primary goal of the experimental pro- gram is the development of deterministic

atom-delivery systems, i.e. devices that

can deliver one and only one atom to a

predetermined location, on demand. In

addition, the Division is a partner in a

project to develop a testbed for quantumcommunication systems, together with

the Atomic Physics Division and the

Information Technology Laboratory.

ACCOMPLISHMENTS

Coherent Matter-Wave

Device Physics

The development of coherent matter- wave sources, based on Bose-Einstein

condensates of dilute atomic gases, has

opened up a new frontier of precision

measurement. There are long-range

prospects for the use of such sources for

sensitive gravitational and inertial sensors,

direct-write atomic lithography, and

quantum information processing. In

collaboration with experimental programs

in Gaithersburg and Boulder, we work on

quantitative studies of the dynamics of

coherent matter-wave systems, with a

particular focus on first-principles modeling and simulation of their dynamics.

One subject of current interest is the

dynamics of ultracold atoms in optical

lattices, a candidate system for quantum

information processing. Optical lattices are

defect-free crystal potentials. Solid-state

crystal structures tend to favor certain

types of lattices and their actual potentials

are very complex. Optical lattices, in contrast, are completely controllable, with the

potentials being perfectly sinusoidal; or,

in general, a sum of sinusoidal potentials.

10
i5r

10 ^1.

-10 -5 0 5 10 15 Potential

X [E J

15

10

>^ 0

-5

-10 -5 0 5 10 15

x[X]

10^

10"

10"

10

Density

Figure 13. Two-dimensional optical lattice

potential (left), and its associated lowest Wannier state (right). Potential and

density distributions are shown.

We have calculated the band structure

for 2D and 3D optical lattices for parameter regimes appropriate to the experiments at NIST. The energy eigenstates

determined by these calculations, known

as Bloch states, are useful for calibrating

lattice properties (e.g., beam orientation

and depth).

As a case study, we investigated the types

of lattices that can be prepared for a 2D

system made by three light fields in the

plane. We showed that, for this simple

arrangement, all five types of 2D lattices

can be made (square, rectangular, centered rectangular, oblique, and hexagonal).

CONTACT: Dr. Charles W. Clark

(301) 975-3709

charles.clark@nist.gov

Atoms on Dennand

Nanotechnology deals with understanding

and manipulating matter on the nanometer scale—that is, on the scale of a few

tens of atoms to a few hundred atoms. As

we gain skill and knowledge in this

regime, the natural question arises, can we go further? Can tools be developed

that work controllably with single atoms

individually, and, if so, what new science

and applications will become available?

With these questions in mind, we have

recently developed a way to reliably isolate one-and only one-atom, essentially

"on demand." Using laser cooling and

trapping techniques, we have isolated

single, cold chromium atoms in a magneto-optical trap, and used feedback control

over the loading and loss processes to

eliminate nearly all the random fluctuations in trap occupation number that

would ordinarily plague such a trap.

Figure 14. Atoms on demand; the chance

of having exactly one atom goes from the random-walk value of 37 % to a value near

100 % by the application of feedback.

The result is a source in which single

atoms can be extracted and replenished

reliably at rates ranging from several tens

of atoms per second in the current configuration to several hundred per second or more in the theoretical limit. Applications

for these deterministically produced atoms

range from fundamental studies of quantum coherence, which take advantage of

the purely quantum nature of isolated

atoms, to structured doping of nanostructures, in which a small, countable number

of dopant atoms is required in nanostructures to tailor their electronic, magnetic,

or optical properties.

CONTACT: Dr. Jabez J. McClelland

(301) 975-3721

jabez.mcclelland@nist.gov

11
iOAL: TO DETERMINE

TOMIC PROPERTIES

,ND EXPLORE THEIR

.PPLICATIONS,

ATOMIC PHYSICS DIVISlOW

The strategy of the Atomic Physics Division is to develbp and apply atonnic-physics research methods

to achieve fundamental advances in measurement science relevant to industry and the technical

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

The first strategic element is to advance the physics

of electromagnetic-matter interactions and to explore

new applications for laser cooled and trapped atoms.

and optical characterization and manipulation of single molecules, biomolecules,

and biomembranes.

Light-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 of

microscopic objects in biochemistry. It

includes both fundamental and applied

studies, such as developing measure- ment 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 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

expehmental projects that contribute to

the understanding and exploitation of

Bose-Einstein condensation of neutral

atoms, matter-wave optics, optical and

magnetic control of trapped-atom collisions, advanced laser cooling and collision

studies for atomic clocks, ultracold plas- mas and Rydberg atoms, the study of

the superfluid to Mott-insulator quantum

phase transition, quantum information

processing, quantum-computing architectures.

ACCOMPLISHMENTS

From an Atomic BEC to MottInsulator to a Molecular BEC

Recent theoretical calculations show how

to obtain a quantum phase transition

that takes the superfluid state appropriate

to a BEC in a shallow, three-dimensional,

optical lattice and transforms it to a Mottinsulator state appropriate to a deep optical lattice. In the superfluid state all the

atoms are identical, whereas in the deep

lattice, Mott-insulator state the atoms are

distinct since they are individually labeled

by their lattice position.

We have shown that if we start with an

average of two atoms per optical lattice

site and increase the lattice depth to

obtain a Mott-insulator state with exactly

two atoms per well site, we can then

convert the atom pairs into ground state

molecules using laser light. Finally after

molecular formation, the Mott-insulator

12
can be "melted" to yield a molecular BEC.

Specific calculations have been done for

the homonuclear species ^^Rbj and the

heteronuclear species KRb.

+ Atoms

Figure 1 . Schematic showing two-color formation of molecules in their ground electronic

state by Raman Photoassociation. In a BEC

this process is initially coherent and leads to

a wavefunction that is both atoms and

molecules.

Studies of atomic BEC systems have

proven to be extraordinarily fruitful, with

connections to a number of disciplines,

including atomic, molecular, and optical

physics, quantum optics, condensed-matter

physics, solid-state physics, quantum

field theory, and quantum information

and computing. One of the primary

purposes of the Mott-lnsulator transition

is the initialization of a neutral-atom

quantum register for quantum computing.

The production of molecular BECs will

extend applications to molecular species.

Experiments along some of these lines

are being planned.

CONTACT: Dr. Carl Williams

(301) 975-3531

carl.williams@nist.gov

Photoassociation in a

Bose-Einstein Condensate

We have investigated the photoassociation of atoms (two colliding atoms

absorbing a photon, forming a molecule)

in a trapped, sodium BEC. We measured

a rate coefficient that exceeds the classical

limit by more than four orders of magnitude. The measured rate coefficient is,

however, in good agreement with results

from a quantum-mechanical two-body

scattering theory. Classically atoms have

to be next to each other to form a molecule, but quantum mechanically the BEC

has a single wavefunction for all the atoms

extending over the entire trapped gas.

This is another example of how the quantum world can give remarkably different

results than the classical world. Such studies

are important for developing theories that

describe the BEC. The theories can then

be used to exploit the BEC as a source of

atoms analogous to the source of photons

from a laser for use in precision measuhng

devices, such as atom interferometers.

CONTACT: Dr. Paul Lett (301)975-6559

paul.lett@nist.gov

Real-Time Measurements of

Antigen-Antibody Binding

Adhesion is an ubiquitous process in biological systems. We have developed a new

technique to study the adhesion of biomolecules in real time under biologically

relevant conditions, similar to the situation

when two cells collide and adhere.

Using optical tweezers, we trap a pair of

microspheres, one coated with an antigen

and the other coated with the corresponding antibody, and bring them close

enough to each other that they repeatedly

collide due to thermally driven motion.

By monitoring the position of the trapped,

antigen-coated microsphere, we can

observe single antigen-to-antibody binding events in real time. We also measure

the single molecule, spontaneous dissociation rate and the average rate at which

antigen-antibody pairs unbind due to

thermal fluctuations. By varying the

number of antigen-to-antibody bonds

that can form in a collision, we can

observe cooperativity in the binding. We

observe not only positive cooperativity,

but also negative cooperativity (which is

rarer in nature) depending on how rigidly

the antigen molecule is attached to the

microsphere surface.

CONTACT: Dr. Kristian Helmerson

(301) 975-4266

knstian.helmerson@nist.gov

Patterned Loading of Atoms

into an Optical Lattice

Quantum systems, such as individual

atoms, can be used as bits of information.

The processing of such information, governed by the rules of quantum mechanics,

is called quantum computing. There is

currently great interest in realizing a quantum computer, which is predicted

to require exponentially less effort than

a classical computer to solve certain

large-scale problems, such as factoring

large numbers.

13
We are developing a processor for quantum infornnation, using neutral atoms

trapped in an optical lattice as the quantum information register. In an optical

lattice, atoms are trapped in the periodic

intensity pattern formed from the interference of intersecting laser beams.

WWVWl Patterned Loading

Figure 2. Diffraction pattern showing the contrast between atoms coherently loading into

every third lattice site, versus every lattice site.

In order to achieve the best performance

for quantum information processing, we

would like atoms tightly confined, which

can be achieved with a short-pehod optical lattice. However, to initialize and read

out the quantum register, we would like atoms in sites spaced more than an optical wavelength apart. We have taken a

major step towards achieving this goal by

loading every third site of a one-dimensional, short-period optical lattice with

atoms from a rubidium Bose-Einstein

condensate.

CONTACT: Dr. James (Trey) Porto

(301) 975-3238

trey.porto@nist.gov

The second strategic element is to develop advanced

optical and x-ray measurement techniques for applications involving laboratory and space plasmas, thin-film

structures, and nanoscale devices.

Plasma and X-Ray

Measurement Methods

INTENDED OUTCOME AND

BACKGROUND

This strategic element focuses on the use

of atomic radiation as an efficient, noninterfering probe of plasmas and industrially important materials. Our research

includes sizable plasmas used for etching

semiconductor wafers, small-scale plasmas

confined in electromagnetic traps, and

nanoscale plasmas induced on surfaces by

individual, highly charged ions. Information

is obtained by measuring the emitted

photons and massive particles using a

variety of instruments, including visible,

ultraviolet, and x-ray spectrometers,

microcalorimeters, mass spectrometers,

submillimeter wave detectors, and spatial

imaging systems. In addition, surface

effects are analyzed at the atomic level

using a scanning tunneling microscope

and an atomic-force microscope.

Our plasma diagnostic research includes

collaborations with industry, university,

and government partners. For example,

Intel and International SEMATECH have

requested that the NI5T electron-beam

ion trap be utilized to assist in the development of EUV lithography light sources.

We work with x rays since their weak

interactions make them a nearly ideal

penetrating probe. The primary goals

of this research are the development

and application of high-resolution x-ray

scattering techniques, the production of

reference samples of thin-film and multilayer structures, and the understanding

of the microstructure of thin-film and

multilayer structures appropriate to the

semiconductor industry.

Following on our experience fielding a

high-energy, curved crystal spectrometer

at the OMEGA laser facility at the

University of Rochester, we are presently

producing a more ambitious, broadband,

multichannel x-ray spectrometer system

for the National Ignition Facility (NIF).

These types of instruments will serve the

plasma-diagnostic community by providing information about such things as the

hot-electron energy distribution and the

plasma temperature.

14
Figure 3. Reflection-geometry spectrometers

constructed as a National Ignition Facility

plasma diagnostic (top). Four convex, curved

crystals (bent to five inches radius of curvature)

together provide cascading high-resolution

x-ray spectral coverage from 1 keV to 20 keV.

The four crystals shown (bottom) are

Potassium Acid Phthalate, Quartz, Silicon,

and Germanium.

The NIST team continues to work on

developing a new crystalline nnaterial that

does not exhibit birefringence at 157 nm

as one approach to ameliorate this problem. This material is based on mixed solid

solutions of CaFs and SrFj, which separately have opposite signs of the effect. Working with industrial partners for

material growth, this new material is

being grown and characterized.

To establish the properties of this and

other UV materials, NIST has developed

a unique phase-shifting interferometer

that can measure the index homogeneity

and birefringence at wavelengths

ranging from the visible through 146 nm

(in the vacuum ultraviolet). It has enabled

a determination of the dispersion of

these properties in this complete

wavelength range.

ACCOMPLISHMENTS

Optical Properties in Support

of UV Lithography

Optical-lithography technology is growing

to more rely upon deep- and vacuumultraviolet radiation in order to further

extend the performance of advanced

integrated circuits. This necessitates the

use of crystalline fluoride materials for the

refractive optics, though little was known

of the optical properties of these materials

at these short wavelengths.

In May 2001, we uncovered a very large,

completely unexpected intrinsic birefringence in calcium fluoride at short wavelengths. Its index of refraction depends

on the polarization of the incident light.

Since then, the 157 nm lithography

community has been struggling to find

ways to design around this aberration.

[001]

Figure 4. Directional dependence of the spatial-dispersion-induced birefringence in calcium

fluoride and related cubic materials, first calculated and measured as part of this project. The

figure shows the previously-unknown heptaxial

behavior (seven nonbirefnngent axes) for this

cubic system.

An effort to characterize many materials

and samples is being pursued to see if a

scaling factor can be established which

reliably provides the 157 nm values from

the much more easily measured visible wavelength values.

CONTACT: Dr. John Burnett

(301)975-2679

john.burnett@ntst.gov

Ion-Gas Recombination Studies

Motivated by a growing interest from the

fusion-energy and astrophysics communities, we have expanded the NIST Electron

Beam Ion Trap facility to allow ion-gas

collision studies. We have installed a gasjet target and additional detectors on our

ion beamline to study the photons that

are emitted as the ions traverse the target.

The new apparatus has yielded measurements on a sequence of charge states of

krypton, starting at Kr^'* and extending

through Kr^^*. The study reveals systematic

changes in x-ray wavelength and intensity

ratios as a function of ion charge state.

Particularly dramatic is an abrupt increase,

by a factor of two, in the La/M ratio as

the L-shell changes from single vacancy

to multiple vacancy. A time-dependent

collisional-radiative model of the excitedstate population distribution confirms that

the origin of this shift is the formation of

metastable states.

CONTACT: Dr. John Gillaspy

(301)975-3236

john.gillaspy@nist.gov

15
Detection of Chemical

Contamination in a

Semiconductor PlasmaEtching Reactor

High resolution, submillimeter wavelength, linear-absorption spectroscopy has

been developed as a tool for monitoring

chemical contamination in plasma-etching

reactors. Contamination may arise from

feed-gas impurities, vacuum-chamber

leaks, and incomplete chamber cleaning.

The submillimeter methods are particularly

sensitive to contamination originating

from water vapor, which has an intense

rotational transition at 557 GHz.

Figure 5. The GEC RF Reference Cell, a

standardized plasma source designed to

create plasmas similar to those found in

commercial semiconductor etching reactors.

We have measured this rotational transition in a Gaseous Electronics Conference

(GEC) reference cell, installed at a commercial company under three different

reactor conditions prior to initiating a

fluorocarbon plasma. The apparatus has

I I OK 1000 K 2000 K 3000 K 4000 K 5000 K 6000 K 7000 K 8000 K 9000 K 10,000 K

Figure 6. Temperature distribution in a high-pressure lighting discharge as revealed by x-ray

absorption imaging.

demonstrated sensitivity levels less than

10 nmol/mol. Levels less than 1 nmol/mol

should be possible.

CONTACT: Dr. Eric Benck

(301) 975-3697

eric.benck@nist.gov

A New Powerful Probe for

High-Efficiency Lighting

There are an estimated 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

metal-halide 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 automobile headlights and

interior lighting.

As a result, there is a growing interest

in increasing their luminous efficiency

through a better understanding of

the processes that govern their operation.

These processes are so complex that they

have defied attempts at predictive modeling or even the development of scalable

design rules.

As part of a cooperative program with

the Electric Power Research Institute, NIST

researchers have used x rays from the

Advanced Photon Source at Argonne

National Laboratory to develop a new

generation of diagnostic methods for

metal-halide lamps. Both x-ray absorption

and x-ray fluorescence were used to map

the distribution of the temperature and

the various elemental components in a

production-style lamp.

The use of these techniques will enable

lighting scientists and engineers to

develop a more complete understanding

of metal-halide arc lamps, leading to

improved design rules, advanced production methods, and eventually, more

energy-efficient lighting.

CONTACT: Dr. John Curry

(301) 975-2817

john.curry@nist.gov

16
The third strategic element is to advance measure

ment science at the atomic and nanometer scale,

focusing on ultraprecise length-displacement measurements, x-ray and gamma-ray precision metrology, and

nanooptics and nanosystems modeling.

Nanoscale and Quantum

Metrology

INTENDED OUTCOME AND

BACKGROUND

Optical and x-ray interferometry is being

used to complete the intercomparison

phase in displacement interferometry. We

are measuring the effect of diffraction on

interferometric measurements through

comparison of Michelson and Fabry-Perot

interferometry. We are evaluating a hybrid

positioning system in which long-range

positioning over 50 mm is provided by a

high-quality commercial translation stage,

and guiding errors are compensated by a

fine positioning stage incorporating a

multichannel closed-loop servo system.

We are also working on the direct link of

a displacement measurement to a cesium

clock by means of a frequency comb. The

goal is to provide the first measurement

of a displacement directly related to the

definition of the meter, without the intervention of a calibrated reference laser.

The wavelengths and energies of x- and

gamma-ray transitions are determined for

applications in crystallography and x-ray

astronomy, for fundamental studies of the

properties of matter, and for the fundamental constants. Crystal diffraction is

the principal measurement tool, and the

lattice spacings of nearly perfect crystals

are determined by comparison to standard

crystals. Diffraction angles are measured

interferometrically or with well-calibrated

encoders. For lower-precision measurements, curved crystals are used with

position-sensitive detectors.

ACCOMPLISHMENTS

Optical Fiber Tapering

System for Supercontinuum

Generation

The frequency comb produced by a

mode-locked femtosecond laser has revolutionized optical-frequency metrology

and is now being applied to displacement

metrology. In order to relate the visible

wavelengths used for interferometry with

an infrared femtosecond laser, we shift

the spectrum of the femtosecond laser by means of nonlinear optics in a fiber that

is tapered to such a small diameter that

the light propagates in the exterior of

the cladding rather than the core.

We have constructed a facility to taper

optical fibers to a well-controlled geometry. The facility consists of four steppermotor-driven stages that simultaneously

pull the fiber as it is being heated by a

very small, traveling flame. By controlling

the oscillatory motion of the flame as the

fiber is pulled, we can force the fiber to

adopt almost any arbitrary shape.

T" I I ~T- 500 600 700 800 900 1000

Wavelength [nm]

Figure 7. Tapered optical fiber shifts the fre- quency spectrum of mode-locked femtosecond

laser output from 850 nm to cover most of

the visible spectrum. The vertical scale is linear;

the scales for input and output are different.

Figure 7 shows the spectrum from a

fiber whose diameter had been reduced

from 125 pm to 2.7 pm and which was pumped at 850 nm. We have successfully

observed the beat from such a fiber and

a helium-neon laser at 633 nm.

CONTACT: John Lawall

(301) 975-3226

john.lawall@nist.gov

Designing the Nanoworld:

Atomic-Scale Simulations

of Nanostructures and

Nanodevices

Atomic-scale simulations of the electronic

and optical properties of complex

nanosystems at the meso/molecular interface are being carried out. These systems

include nanocrystals, self-assembled dots

(as shown in Fig. 8), nanodot arrays and

solids, molecular electronics, biomolecules,

and bio/nanohybhds.

17
Atomic-scale variations in geometry, size,

shape, and composition critically impact

the functionality of these nanosystems.

For example, our simulations show that

the optical response of arrays of nanodots

can be turned on or off simply by changing the number of atoms between the

dots. Our studies of doped fullerenes show that dopants exist for p- and n-type

doping, that these doped fullerenes can

be combined to form molecular rectifiers,

and that their properties can be tailored

as dopant atoms are added one-by-one.

The fourth strategic element is to produce reference

data on atomic structure and to critically compile

reference data for scientific and technological applications.

Figure 8. Schematic of a self-assembled

pyramidal quantum dot. Atomic positions

used in the modeling are indicated.

These simulations provide benchmarks

for precision experimental 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.

CONTACT: Dr. Garnet Bryant

(301) 975-2595

garnett.bryant@nist.gov

Critically Evaluated

Atomic Data

INTENDED OUTCOME AND

BACKGROUND

The objective of this strategic element

is to critically compile fundamental

constants and atomic spectroscopy data

from the far infrared to the x-ray 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.

The NIST databases for atomic spectra

and fundamental constants are recognized throughout the world. The Atomic

Spectroscopic Database on our website

now receives about 80,000 downloads

per month, up from 60,000 only two

years ago. The principal users are plasma

physicists, crystallographers, astronomers,

lighting engineers, and spectrochemists.

However, the databases are still far from

complete, and the quality of the data available in the literature from which the databases are built is 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. When accurate, reliable data do not exist for high priority needs, specific measurements or calculations are undertaken to produce them.

ACCOMPLISHMENTS

New X-Ray Wavelength Table

in Review of Modern Physics

important experimental and theoretical

developments in the field of x-ray transitions have made the mid-1960s database

of these transitions obsolete. On the

experimental side, x-ray wavelengths can now be more accurately linked to optical

wavelengths and the SI definition of

length, through combined x-ray and optical

interferometry. In addition, a number of

recent, accurate x-ray measurements, and

updated values of the fundamental physical constants, are available to be included

in the database. On the theoretical side,

there has been continued development of

better calculational procedures that produce results in excellent agreement with

experiment. This good agreement creates

the possibility that theoretical values can

provide rather good estimates of missing

or poorly measured experimental data.

In collaboration with theorists in France

and Sweden, we have produced a new

reference x-ray wavelength table that is

being published in Reviews of Modern

Physics. The new table is the culmination

of a long-term NIST effort to produce an

improved, comprehensive data resource

for x-ray transition energies. It contains

18
K- and L- x-ray transition and absorption

edge energies for all elements from neon

to fermium. It includes carefully selected

and evaluated experimental data robustly

connected to the SI definition of length,

and accurate, state-of-the-art theoretical

estimates. The new x-ray wavelength

table will soon be available also on the

NIST Physics Laboratory website.

CONTACT: Dr. Ernest Kessler

(301) 975-4844

ernest.kessler@nist.gov

Handbook of Basic Atomic

Spectroscopic Data

To meet increasing needs for reference

spectral data for neutral and singly-ionized atoms, we completed a new database of wavelengths, energy levels, and

transition probabilities for the most

important transitions in all elements

from hydrogen to einsteinium.

This Handbook of Basic Atomic Spectroscopic Data lists wavelengths and intensities for over 12,000 transitions. Energy

levels and transition probabilities are given

for about 2400 of the strongest lines,

taken from over 400 references. Data for

individual elements can be accessed by

name, atomic number, or atomic symbol.

A finding list is available to assist in

identification of possible impurities in

an observed spectrum.

This handbook will be published in standard paper format, in an e-book that

combines ease of use and portability, and

in an electronic version on the Physics

Laboratory website.

CONTACT: Mrs. Jean Sansonetti

(301) 975-4725

jean.sansonetti@nist.gov

Precision Measurement

of Laser Wavelengtlis for

157 nm Microlitliography

The next generation of microlithography

tools will be based on a molecular-fluorine

laser operating at 1 57 nm. In order to design

optical systems for focusing ultraviolet

radiation from the laser onto the chip

substrate, the index of refraction of the

optical materials must be known to high

accuracy. Since the index of refraction

varies rapidly with wavelength, it is

chtical that the wavelength of the laser

also be accurately known.

To obtain accurate wavelengths for the

laser, we used the NIST 10 m vacuum

spectrometer to measure the lasing lines

from a commercial laser in the region

of 1 57 nm. The experiment was conducted in collaboration with an excimer laser

manufacturer, which supplied the laser.

The spectra were calibrated by spectral

lines from a platinum hollow-cathode

lamp that had been measured by NIST

and used to calibrate spectrometers

on the Hubble Space Telescope. The high

accuracy of these measurements relied on

a specially designed system to illuminate

the spectrometer in such a way as to

eliminate small shifts between the spectrum of the lasing lines and that of the

calibration lamp.

Wavelengths of six lasing lines were

measured to an uncertainty of ±0.0001 nm.

Three of the lines were newly observed

lasing lines.

CONTACT: Dr. Craig Sansonetti

(301) 975-3223

craig.sansonetti@nist.gov

19
GOAL: TO PROVIDE THEI

FOUNDATION OF OPTICAL

RADIATION MEASUREMENTS

FOR OUR NATION.

OPTICAL TECHNOLOGY DIVISION

The strategy for meeting this goal is to develop and provide national nneasurement standards and services

to advance optical technologies spanning the ultraviolet through the nnicrowave spectral regions.

The 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 promoting the use

of optical technology by undertaking

research and development to 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 measure- ments between and within organizations.

A significant part of the Division's activities

includes participation in international

comparisons of measurements with other

national metrology institutes 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 radiomethc 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 most accurate optical-power

measurements by directly comparing

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 less than 0.02 %. This will be

reduced to 0.01 % with the completion

of HACR 2.

The improvements realized by tying the

radiometric measurements to a cryogenic

radiometer are significant. Recently the

Division's spectral-irradiance scale, as

disseminated by FEL lamps, was converted

to a detector-based scale traceable to

optical-power measurements performed

by HACR. The improved detector-based

scale has led to a reduction of the spectralirradiance uncertainties by a factor of

two for ultraviolet and visible radiation,

and a more significant reduction for

infrared radiation.

These activities 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

new research uses synchrotron radiation

from an electron-storage hng, the recently

upgraded NIST Synchrotron Ultraviolet

Radiation Facility (SURF III), as a source

of continuously tunable, intense

ultraviolet radiation.

20
ACCOMPLISHMENTS

Detector-Based Radiance and

Radiance-Temperature Scales

We have reduced the uncertainties of the

present, source-based, spectral-radiance

and radiance-temperature scales by

converting to detector-based scales.

These scales are tied to an absolute

imaging pyrometer (API). We calibrated

its absolute radiance responsivity at the

SIRCUS facility, using a tunable, laserilluminated integrating sphere as the

source of spectral radiance. The spectral

radiance is traceable to silicon trap detectors calibrated for absolute power responsivity against HACR and a set of apertures

of known area to define the geometry.

Measurements performed with API of the

freezing point of a high-emissivity blackbody cavity in contact with molten gold

reveal a noise-equivalent temperature

of 2 mK (/c = 2) at 1337 K. The total

uncertainty of the measurements, about

1 20 mK {k - 2) at this temperature, is

due to the combined uncertainties arising

from the radiance-responsivity calibrations, the size-of-source effect, and the

long-term stability of the pyrometer.

In concert with the API development,

we have performed radiance-temperature

measurements of a 2950 K high-temperature blackbody (HTBB), comparing both

conventional source-based and newer

detector-based measurement methods.

The source-based approach uses measured radiance relative to a gold-point,

fixed-temperature blackbody to assign the

temperature to the HTBB as prescribed

by the International Temperature Scale

of 1990. The detector-based approach

uses a set of filter radiometers to assign a

temperature to the HTBB. Their spectralirradiance responsivities are traceable to

the HACR optical-power scale through

the Division's Spectral Comparator Facility

The spectral-irradiance responsivities are

converted to spectral-radiance responsivities by an appropriate choice of precision

apertures and measurement geometries.

The aperture areas required in the analysis

are determined using an optical coordinate-measuring machine.

The net result: we demonstrated a

detector-based temperature uncertainty

of 0.21 K{k = 2) at 3000 K, more than

a factor of six better than the sourcebased approach.

CONTACT: Dr. Howard Yoon

(301) 975-2482

howard.yoon@nist.gov

SURF III as an Absolute

Source of Spectral Irradiance

An experiment was undertaken to verify

that the absolute spectral irradiance from

the NIST Synchrotron Ultraviolet Radiation

Facility (SURF III) can be predicted using

the Schwinger relativistic electrodynamical

model for synchrotron radiation and

knowledge of the electron-beam energy,

current, and radius.

The study was performed on Beamline 3,

recently developed for absolute, sourcebased, ultraviolet radiometry at SURF III.

The measurements consisted of characterizing the angular spread of the radiation

from SURF III in the direction perpendicular to the orbital plane of the electron

beam. Because of the highly relativistic

speed of the electron beam, the angular

spread is narrowly confined to within a

fraction of a degree of the orbital plane.

Narrow-band filtered radiometers, with

spectral responsivities measured to 0.1 %

relative uncertainty {k = 2) at the SIRCUS

facility, were used to directly measure the

radiation emitted from a tangential source

point of the ring, from the near ultraviolet

to the infrared.

The experiment demonstrated agreement

with theory to within 0.5 %. Such excellent agreement not only confirms the

Schwinger theory, but it also connects the

detector-based spectral-irradiance scale,

based on SIRCUS and cryogenic radiometry,

to the source-based scale of SURF III. The

study further validates Beamline 3 as a broadband standard of spectral irradiance

for the absolute calibration of optical

instruments and for the calibration of

deuterium and FEL incandescent lamps

as secondary or transfer standards.

CONTACT: Dr. Ping Shaw

(301) 975-4416

shaw@nist.gov

Second-Generation

High-Accuracy Cryogenic

Radiometer (HACR 2)

A second-generation cryogenic radiometer

is under development to further reduce

the uncertainty in our optical-power

measurements. The expected factor-of- two reduction in the power-measurement

uncertainty will affect many of the radiometric and photometric scales maintained

in the Division and presently tied to the

first-generation HACR.

21
The second strategic element is to develop novel

optical measurement methods for solving problems

in critical and emerging technology areas.

The new instrument is designed to have

a greater dynamic range, from 1 fxW up

to 70 mW in power, faster response time,

lower noise figure, and improved modular

construction. It will be installed in the

SIRCUS facility, providing ready access to

a variety of lasers. These lasers allow a

broad range of wavelength and power

levels to be selected for scale transfer to

silicon trap detectors, further reducing the

uncertainties in the measurement chain.

Additionally, the modularity of the detector section permits new detector modules

to be designed and built, optimized for

specific wavelengths and power levels.

CONTACT: Dr. Joseph Rice

(301) 975-2133

joe.rice@nist.gov

Figure 1. Jeanne Houston and Joe Rice

preparing to calibrate a silicon-photodiode

trap detector using our second-generation

High Accuracy Cryogenic Radiometer, HACR 2.

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

non-linear laser and near-field techniques

to characterize thin-films, surfaces, and

interfaces important in molecular biology,

polymer science, and nanotechnology

In biophysics and heath care, new optical

methods based on surface-enhanced

Raman spectroscopy and confocal, fluorescent, imaging microscopy are being

developed for the investigation of single,

biological molecules. This is part of a larger,

inter-laboratory 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 in rapid thermal processing,

to develop optical-scattering metrology

for the next-generation wafer inspection

tools, and to develop chemical diagnostic

methods for reactive, ion-etching plasmas

using submillimeter spectroscopy

Ultraviolet-radiation metrology is being

developed to ensure a measurement

infrastructure for 1 57 nm and shorterwavelength lithography leveraging the

unique ultraviolet-radiometry capabilities

of SURF III to target needs in opticalmaterials properties, detector radiationdamage characterization, and laser-power

measurements.

In response to recent events, our support

of optical-radiation measurements for homeland security has increased, building

on expertise developed through the NIST

Director's competence program in THz

Metrology We are investigating femtosecond-pulsed THz spectroscopy for the

detection of biological-warfare agents in

paper envelopes that are effectively transparent in the THz spectral region, and

continuous-wave THz spectroscopy for

the sensitive detection of chemicalwarfare agents.

We are also using our unique expertise in

correlated-photon radiometry to develop

novel, single-photon-on-demand sources

for secure quantum cryptography in

collaboration with other PL Divisions.

22
ACCOMPLISHMENTS

Optical Scattering by

Nanoparticles on Si Wafers

Light-scattering metliods were developed

to allow accurate measurement of the

diameters of standard reference particles

bound to silicon substrates. This was in

response to the semiconductor industry's

need for improved metrology of particles

and other defects on silicon wafers. The

identification and quantification of such

defects are required to facilitate the transfer of wafers from the factory to the chip

manufacturers, and to locate and diagnose problems in the chip fabrication line.

To calibrate inspection tools, and thus

to assure agreement between the wafer

and chip manufacturers, the industry

intentionally deposits accurately-sized,

polystyrene spheres onto reference

wafers. Because the deposition process

can lead to changes in the size distribution of the particles, techniques are

required to accurately determine the

diameters of the deposited particles.

To address this need, we did a combined

theoretical and experimental investigation

of the optical properties of subwavelengthdiameter spheres on surfaces. The

Bobbert-Vlieger theory of light scattering

by a spherical particle on a flat substrate was extended to account for films on

both the substrate and the particle,

and then validated by measurements

on deposited, polystyrene and copper

nanospheres. The copper spheres provided a particularly demanding test of the

theory due to the presence of a strong

near-field interaction between the conducting spheres and the silicon substrate.

To assess the measurement uncertainty of

the diameter of the particles, the effects

of non-sphericity, size distribution, and

doublet formation were investigated.

The modal diameter of the 100 nm polystyrene sphere standard (SRM® 1963) was determined to be 99.7 nm with an

uncertainty of 1 .7 nm (k = 2), in excellent

agreement with aerosol measurements.

The technique is presently being incorporated into semiconductor industry standards.

CONTACT: Dr. Thomas Germer

(301) 975-2876

germer@nist.gov

Single-iVlolecule Optical

Probe of Binding in

Antibody-Antigen Force

Measurements

As part of a NIST-wide competence

program in Single-Molecule Measurement

and Manipulation (SM^), we are developing

sensitive, single-molecule, spectroscopic

and imaging techniques for incorporation

into MEMS-based, molecular-screening

platforms.

One technique recently developed uses

single-molecule fluorescence spectroscopy

to monitor atomic-force measurements.

Individual Alexa-488 dye molecules are

(A)

2 |jm

tethered to a glass substrate in an aqueous

buffer solution. The sharpened tip of a

microfabricated cantilever, with Alexa-488

antibodies attached by 200 nm long poly- mer tethers, is positioned over the dyeprepared surface. As the tip is lowered

onto the surface, the cantilever deflection

and the laser-driven single-molecule fluorescence from the surface dye molecules

are monitored (Fig. 2). At some time during

an approach, an Alexa antibody may bind

to an Alexa dye molecule, quenching its

fluorescence. The shape of the force curve

and the recovery of fluorescence verify

binding as the cantilever is retracted and

the bond is broken.

Force assays are widely used in biology

to elucidate binding and folding dynamics

of proteins and DNA or RNA. The addition

of independent, optical verification of

single-molecule binding helps distinguish

true binding events from other interactions that commonly interfere with

these assays.

CONTACT: Dr. Lori Goldner

(301) 975-3792

lori@nist.gov

Figure 2. (A) Fluorescence image of single

Alexa dye molecules on glass. (B) Illustration of

a simultaneous force and optical data sequence,

showing how cantilever deflection changes as

the tip approaches, binds, and retracts.

(B)

Cantilever

Deflection (Force)

Fluorescence

(Photon

Counter)

Approach Bind & Contact QuenchUnfold

23
In situ Nonlinear Vibrational

Spectroscopy for Biological

Interfaces

In collaboration with CSTL, Doubly

Resonant Sum Frequency Generation

(DR-SFG) spectroscopy is being developed

as a sensitive molecular probe of biological interfaces important for biosensors,

DNA arrays, tissue-engineering research,

and the understanding of cell-membrane

structure and function.

The method relies on the enhanced nonlinear mixing of infrared and ultraviolet or

visible laser beams at an interface when

both lasers are resonant with molecular

transitions, typically a vibrational transition

for the infrared laser and an electronic

transition for the visible or ultraviolet laser. Femtosecond laser technology and nonlinear optics are used to generate spectrally

broad, infrared pulses between 2.5 pm and

12 (jm, which are mixed with picosecond

ultraviolet or visible laser pulses at the interface to generate an entire broadband DRSFG spectrum at high signal-to-noise ratio.

The approach was used to measure the

first ultraviolet (270 nm) DR-SFG spectra

of DNA base dimers tethered to a goldcoated surface using thiol attachment

chemistry. Figure 3 presents DR-SFG

spectra of oligomers of the DNA bases

adenine (A), cytosine (C), and guanosine

(G), all of which have electronic transitions in the 260 nm to 270 nm range to enhance the SFG effect. The vibrational

modes were identified by analogy to ultraviolet resonance-Raman spectra at the same 270 nm wavelength. For instance,

the intense feature for adenine near 1600 cm'^ corresponds predominantly

to the in-plane stretching motion of the

carbon atoms, C4 and C5, linking the

double ring of the purine.

The dependence of the amplitude of DRSFG features on the polarization direction

of the laser beams will permit the spatial

orientation of the molecules to be deduced.

The method is being extended further

into the ultraviolet to 200 nm to allow

the investigation of peptides and proteins.

CONTACT: Dr. Kimberly Briggman

(301) 975-2358

kbriggma@nist.gov

T3

1440 1480 1520 1560 1600 1640 1680 1720 1760 1800

Vibrational Frequency [cm"'']

Figure 3. DR-SFG spectra of DNA bases A, C, and G tethered to the surface via a thiolate

linkage: Au-S-(CH2)6-Base-Base.

Terahertz Spectroscopy

of Biological Molecules

Novel THz spectroscopy and imaging

methods are being developed and

demonstrated as part of a NIST competence program on Advanced Terahertz

Metrology The methods are being applied

to characterize the molecular structures,

intramolecular force fields, low-frequency

concerted motions, and conformational

dynamics of biological molecules.

Continuous-wave and pulsed THz spectra were recorded for a large number of

amino acids, peptides, sugars, carbohydrates, and vitamins at room temperature

and at liquid-helium temperature. The

complex spectra reveal distinct absorption

features and patterns that provide information on the molecular conformations

and the vibrational and intramolecular

force fields.

A collaborative study with the NIST Center

for Neutron Research and the Institut

Laue-Langevin in Grenoble, France, is

attempting to interpret these spectra,

building on a previous, successful modeling of the neutron-scattering, vibrational

spectrum of crystalline glucose.

The unique signatures of these biological

molecules has led to an effort to use THz

spectroscopy for identifying chemical- and

biological-warfare agents in paper and

plastic packaging that is transparent to THz radiation. We have measured the THz

spectra of about one hundred common

materials and biological samples and compiled a modest database for this purpose.

This DARPA-funded project is being undertaken in collaboration with SPARTA, Inc.

CONTACT: Dr. Edward Heiiweil

(301) 975-2370

ejh@nist.gov

Single-Photon-On-Demand

Sources for Quantum

Cryptography

The security of quantum cryptography

and communication schemes depends

on the use of single photons to carry information. Parametric down-conversion (PDC),

24
which produces photons in correlated

pairs, is the basis for one type of singlephoton source. Unfortunately, present

single-photon sources are generally incapable of producing single photons

on dennand with high probability, while

simultaneously suppressing the probability

of yielding two or more photons. This

compromises the overall security of the

communication. One reason PDC-based

schemes have this problem is because

they employ photon-counting detectors

which cannot discriminate whether just one or a burst of photons was detected.

In response to the need for an improved,

on-demand, single-photon source, we

have proposed a multiplexed version of

the PDC scheme that allows independently

adjustable probabilities for producing one

and more than one photon. The system

operates by collecting multiple pairs of

correlated photons from the ring of

correlated photon pairs azimuthally

distributed around the PDC pump-laser

propagation axis, as pictured in Fig. 4. The scheme allows a single, conventional,

photon-counting detector to better

approximate a true "photon-number"

detector, which in turn allows the overall

system to better approximate a true

single-photon source.

A recent experimental test of this concept

with four channels was successful.

CONTACT: Dr. Alan Migdall

(301) 975-2331

alan.migdall@nist.gov

Heralded Photon

Delay Processor

Figure 4. Multiplexed

version of a parametric

down-conversion

scheme for producing

single photons on demand.

The third strategic element is to disseminate optical

radiation measurements and standards to industry,

government, and academia.

Optical Measurement

Services

INTENDED OUTCOME AND

BACKGROUND

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

needs for standards and specialized measurements by government and industry.

These facilities are available to government and industry customers through

formal calibration services, special tests,

and standard reference materials offered

through NIST Technology Services or

through collaborative research efforts.

We maintain facilities for optical-properties measurements of reflectance, transmittance, and gloss; for photometric

measurements including luminous intensity

and color temperature; and for radiometric measurements, including spectral

radiance, spectral irradiance, spectral

responsivity and radiance temperature.

The Division has highly specialized facilities

for performing low-background radiometric

measurements, for characterizing remotesensing instruments, for measuring the

area of precision radiometric apertures,

and for determining the absolute optical

power, radiance, and irradiance spectral

responsivities of instruments. New meas- urement facilities under development

include reflected color, emittance, retroreflectance, and ultraviolet spectral irradiance.

The Division strives to ensure the quality

of these programs by publishing our

research and measurement methodologies

Figure 5. Charles Gibson preparing a blackbody-radiation source for calibration of

spectral irradiance.

25
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 offering formal short-courses in

Photometry, Spectroradiometry, and

Radiation Temperature Measurements.

ACCOMPLISHMENTS

High-Accuracy, DeepUltraviolet, Index of

Refraction Measurements

at SURF III

A new beamline (BL-5) was completed

at the NIST Synchrotron Ultraviolet

Radiation Facility (SURF III), equipped with

a high-resolution, deep-ultraviolet, Fouriertransform spectrometer (DUV-FTS) to

measure the index of refraction of materials,

with high accuracy In contrast to the

traditional, prism-goniometer measurement

of the refracted angle, the DUV-FTS

analyzes the fringe pattern in the transmittance spectrum of an etalon made

from the sample material.

Using independent measurements of the

sample thickness and fringe order, we

determined the index of refraction with

uncertainties (- 10"^) similar to that of the

classical prism method. The interferometer

approach offers significant advantages

over the prism method, including greater

speed, continuous wavelength coverage,

and the ability to measure thin samples

such as absorbing fluids.

1.52

S 1.50 cq

o

2 1.48

H—

CD

1.46

1.44

\ 1 10"'

.\ 5

10"*

\

^ \ -SIO"*

200 300 400 500 600-

Wavelength [nm]

200 300 400 500

Wavelength [nm]

600

Figure 6. Index of refraction of CaFj measured

with the DUV-FTS at SURF III. The solid circles show the measured values, and the solid line shows a three-term Sellmeier fit, whose

residuals are shown in the inset.

Initial results at room temperature on a

1 mm thick CaFj sample at wavelengths

between 175 nm and 600 nm are shown

in Fig. 6. The solid circles indicate the

measured index values, while the solid

line is the result of a three-parameter

Sellmeier fit. The residuals from the fit, shown in the inset, are approximately

5 X 10"*. Comparison to our previous

prism measurements on CaFj at 193 nm

shows agreement within 1 .3 x 10^^

consistent with the estimated combined

uncertainties in the two measurements.

Plans are undenA/ay to extend the range

to below 1 57 nm for measuring optical

materials important to the deep-ultraviolet

photolithography industry. Measurements

are also planned on deionized water at

193 nm, which is under consideration for

immersion photolithography.

CONTACT: Dr. Keith Lykke

(301) 975-3216

keith.lykke@nist.gov

New Reference Colorimeter

We have constructed and are presently

testing a new reference instrument for

measuring the reflectance color of

materials. This project was undertaken

in response to industry and government

demands for improved color measure- ments and standards, as articulated in

the 6* and 7* Reports of the Council for

Optical Radiation Measurements (CORM).

Improved color standards are required to

ensure better color matching of products

manufactured at different sites. Because

the color of a product often plays a major

role in its acceptability, color measurements and standards are extremely

important to industry.

Our new instrument performs measure- ments for all possible combinations of

illumination and viewing angles, including

the standard 0745° and 67diffuse geometries, allowing the complete characterization of the reflectance properties of an

object. The popular 0/45 measurements

are highly automated through a sample

wheel with a capacity for 20 samples,

as shown in Fig. 7.

Figure 7. Maria Nadal prepares the NIST

reference colorimeter

26
We did a complete uncertainty analysis,

considering wavelength accuracy straylight rejection, reproducibility of sample

positioning, and signal noise. A critical

aspect of the analysis was the inclusion of

the statistical correlation between signals

at the same wavelength and between

reflectance factors at different wavelengths. The estimated measurement

uncertainties are A£ab < 0-4, where AE^t, = 1 is generally taken as the threshold for

visual discrimination between two colors.

CONTACT: Dr. Maria Nadal

(301) 975-4632

maria.nadal@nist.gov

Thermal-Infrared

Transfer Radiometer Verifies

Radiance Scales Used in

Earth Remote Sensing

To establish the traceability of radiometric

measurements performed by the remotesensing community to NIST's radiometric

scales, and to perform on-site calibration

verifications of critical remote-sensing

instruments, we have developed the

transportable Thermal-Infrared Transfer

Radiometer (TXR). Such traceability helps

ensure that the measurements undertaken

by this community are of the highest

accuracy and can be compared to similar

measurements performed by other

countries or at other times.

The TXR was deployed at the University

of Miami's Rosenstiel School of Marine

and Atmospheric Sciences, in collaboration with NASA-Goddard, to verify the

radiance scales of several blackbody

sources used by the sea-surface remotesensing community to calibrate ship-

»based radiometers. These, in turn, validate

satellite measurements of sea-surface temperature. The radiometer was then sent

to ITT Industries in Ft. Wayne, Indiana, to measure the radiance of two calibration

targets used to verify the calibration of

the NOAA Geostationary Operational

Environmental Satellite (GOES) imagers.

A third deployment was made to Los Alamos National Laboratory, to measure

the radiance of blackbody sources in a

cryogenic vacuum chamber previously

used to calibrate a space-flight instrument

for the Department of Energy.

The success of these deployments has led

to new efforts to improve the calibration

of the TXR and to extend its operational

range to temperatures below 288 K by

performing the measurements in a lowinfrared-background, liquid-Ng-cooled, vacuum test chamber To do these measurements, the NIST Medium-Background

Infrared (MBIR) facility was used to

calibrate the TXR against a high-accuracy

cryogenic blackbody in conditions that

simulate outer space. The facility allowed

the extension of the TXR radiance scale down to 200 K and enabled the evaluation of measurement uncertainties due

to room-temperature infrared background

radiation and atmospheric infrared

absorption and emission.

CONTACT: Dr. Joe Rice

(301) 975-2133

joe.rice@nist.gov

Wire-Contrast

Measurement Standards

We developed a new facility to measure

the contrast of ultraviolet-laser-written

markings on electrical wires used in aerospace and military vehicles, in response

to a request by the Navy for improved

standards in this area. Although the ultraviolet-laser-written markings are immune

to fading with age, the gray color of the

writing reduces the visual contrast relative

to black-ink markings. A high contrast

level is desirable for these markings to

ensure the correct identity of a wire

during installation, repair, or maintenance.

Writing-contrast values of 60 % or higher

are recommended by industry standards.

However, the measured values for the same wire sample often vary by as much

as 10 % to 20 %.

Our new reference instrument consists

of a well-characterized luminance meter

with a microscope to measure the luminance on a circular spot of 12 pm diameter or larger. The wire is illuminated by a

fiber-optic source with a known spectral

distribution. A three-axis translation stage

under computer control automatically

scans the wire surface. The computer

also acquires and analyzes the data.

The instrument characterization yields an expanded relative measurement uncertainty

of better than 2 % for typical wire colors

and sizes.

A formal calibration service is being

established for both standard wires

and contrast-measuring instruments.

CONTACT: Dr. Yoshi Ohno

(301) 975-2321

ohno@nist.gov

27
IONIZING RADIATION DIVISION

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

standards for ionizing radiation and -radioactivity to meet national needs for health care,

U.S. industry, and homeland security.

The first strategic element is to develop and provide

standards for radioactivity based on the SI unit,

the becquerel, for homeland security, environmental,

medical, and radiation protection applications.

Radioactivity Standards

INTENDED OUTCOME AND

BACKGROUND

The Radioactivity Group 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.

A vigorous program is underway to develop

microcalorimetric methods to measure power from radioactive sources. This work

is proceeding in parallel with liquid-scintillation detector methods based on triple-todouble-coincidence ratio (TDCR) counting.

Accurate activity measurements over a

broad dynamic range are obtained using

these two complementary techniques.

For ultra-low-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.

Figure 1 . Dr. Leticia Pibida adjusting laser

optics for resonance ionization mass

spectrometry (RIMS).

The Radioactivity Group also provides

leadership in a national program for radiopharmaceutical standards. We provide the

national standards for radionuclides used

in 13 million diagnostic procedures and

200,000 therapeutic nuclear medicine

procedures annually in the U.S. This work

has been expanded to include radioactivity

measurements of brachytherapy sources

used to prevent restenosis following

balloon angioplasty

With heightened concern in the U.S.

regarding terrorists' attacks using radiological or nuclear weapons, we are leading a national effort to develop standards

and protocols for radiation instrumentation for first responders. Initial efforts

are directed towards four areas:

1) equipment standards and test methods for hand-held detectors

for first responders;

2) a testbed for cargo-container and

truck inspections for radiological

and nuclear materials;

3) radionuclidic forensic 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 regulationdriven, performance evaluation programs

of limited scope. The fundamental flaw

28
that the metrology community recognizes

is that there is a lacl< of direct linkage to

national radioactivity standards. This situation is being addressed in the publication

of three ANSI standards. These consensus

standards call for a traceability-testing

program that links the quality of operational

measurements to the national standards.

ACCOMPLISHMENTS

Cargo-Container

Inspection System

The smuggling of materials or weapons

in shipping containers represents a clear

threat to the U.S. Major radioisotopes of

concern are predominantly the plutonium

and highly enriched (weapons grade)

uranium isotopes, as well as some of

their fission products, e.g., '°Sr and ^^'Cs.

These are the key ingredients of nuclear

fuel and nuclear warheads. The threat

also includes radioisotopes primarily used

in industrial and medical applications,

such as ^"Co, ^"Cs, ^'°Tm, ^"Ir, ^^'1, ''"^Tc,

'"'Am, and "'Ra.

We are developing a cargo-container

inspection testbed to provide a means

for calibrating detectors used for radioactivity measurements in the field. This

testbed is outdoors to simulate actual

operational conditions. Different kinds

of standard radioactive sources will be

placed inside a cargo container, so that

different kinds of detectors can be tested

and calibrated to optimally detect and

measure the sources. Computer modeling

will be used to confirm changes in effectiveness due to possible geometrical

changes of the sources with respect to

the detection system, and to predict

the shielding effect of other materials

in the container.

The goal of this work is to develop a

standard container and measurement

protocol, so manufacturers can calibrate

their detectors, and users can develop

criteria, for radiological detection in

ports of entry in the U.S.

CONTACT: Dr. Leticia Pibida

(301) 975-5538

leticia.pibida@nist.gov

Gamma-Ray

Spectrometry System

Due to increased concerns about a possible

terrorist attack using radioactive materials

in dispersal devices, we have initiated new

research in gamma-ray measurements.

Information about the equipment required

for these kinds of measurements is of

great importance.

Two new CdZnTe detectors were tested,

and their ability to detect gamma-ray

emitting sources was compared with

existing High-Purity Germanium and

Nal(TI) detectors. Because these detectors

all can operate at room temperature, they

are attractive candidates for field measurements. The detectors' efficiency, detection limits, and energy resolution were

measured to determine their performance

and the circumstances under which they

could be used.

The measured energy resolution of the

CdZnTe detector is better than that of the

Nal(TI) detector, but its efficiency is lower,

mainly due to the smaller crystals that are

presently available in the market. On

the other hand, its small size can be an

advantage for measurements in confined

and narrow places, and it has low power

consumption. It may be the best choice

for monitoring relatively high-level source movement or dispersal.

CONTACT: Dr. Leticia Pibida

(301) 975-5538

leticia.pibida@nist.gov

Microcalorimetry for

Absolute Radioactivity

Standardizations

A new, primary standardization capability

has been established at NIST to provide

standardizations for rather large, GBqrange, brachytherapy sources. In addition

to the dual-compensated, cryogenic

calorimeter operating at = 8 K, a commercial "isothermal microcalorimeter" has

been adapted and evaluated for use in

performing classical, calorimetric-based

standardizations.

This dual-cell, near-isothermal (heat flow)

calorimeter operates at near-ambient

temperatures, utilizes specially-fabricated

source-holder cells that are used to maximize the energy absorption of the ionizing

radiation, and incorporates resistance

heaters within these measurement cells

to obtain very-accurately-determined,

independent, power calibrations.

Evaluations were initially performed on two different types of intravascular

brachytherapy sources containing nuclides

that decay by pure p emission, viz.,

(1) a stainless-steel-jacketed s°Sr-'°Y

source with a highly-refractory, ceramiclike, inner matrix, and (2) a "hot-wall"

balloon-catheter source that consists of

a thin film of ^^P enveloped between

29
polyethylene walls. The measured thermal

power was related to source activities

through the use of calculated average

energies per decay, and was compared

against known source activities determined from previous radioanalytical

destructive assays. Monte Carlo calculations for the energy deposition in the

measurement cells were used to correct

for power losses due to escaping

ionizing radiation.

This verification work clearly demonstrated,

quantitatively that the "isothermal"

microcalorimeter was sufficient for

performing primary calibrations.

CONTACT: Dr. Ronald Colle

(301) 975-5527

ronald.colle@nist.gov

New Technique for

Absolute Standardization

of Radionuclides

Beta-emitting radionuclides make up the

majority of nuclides used in nuclear medicine. Because of its high detection efficiency,

liquid scintillation counting (LSC) is the

preferred method for calibrating these

radionuclides. Traditional applications of

LSC require the use of tracers, such as ^H,

and a calculational model to determine

the detection efficiency for the nuclide

under investigation. The Triple-to-Double

Coincidence Ratio (TDCR) method is a

new, quasi-absolute, LSC technique that

can determine the counting efficiency

for a radionuclide, without the use of

an external tracing standard.

We have constructed a TDCR spectrometer

with three phototubes and the electronics

to process 2- and 3-fold coincidences of

detected photons emitted from the liquid

scintillator medium. We measured its

operating characteristics using solutions

of NIST SRMs for (tritiated water) and

"Ni. The TDCR-measured activities agree

with previously certified values to within

0.04 % and 0.2 %. We now can calibrate

radionuclides encountered in nuclear medicine with shorter sample preparation times

and with less, long-lived, radioactive waste.

CONTACT: Dr. Brian Zimmerman

(301) 975-5191

brian.zimmerman@nist.gov

Workshop on

Standards for Important

Radiotherapy Nuclide

The American Cancer Society estimates

that there will be a total of 64,000 new

cases of lymphoma in the U.S. this year,

with an expected five-year survival rate

(for non-Hodgkin's lymphoma) of 52 %.

A new drug for treatment of this disease

is Zevalin, which is a monoclonal anti- body labeled with the radionuclide '"Y.

While has many properties that make

it suitable for use in radiotherapy, those same properties present a number of

challenges regarding its measurement.

Anticipating imminent FDA approval of

Zevalin and an exploding need for standards and measurement quality assurance

for other radiopharmaceuticals using

this nuclide, NIST held a workshop in December 2001 to address the measure- ment issues. Invited speakers included

representatives from NIH, radiopharmaceutical manufacturers, radiopharmacies,

isotope producers, government regulators,

and NIST

Figure 2. Michelle Millican preparing radioactivity standards for a radiotherapy nuclide.

Among the concerns expressed by the

46 participants were the need for more

frequent distribution of standards for '"Y

(currently once a year), a desire for NIST

to issue '°Y solution standards in clinically

useful geometries instead of the standard

NIST 5 mL glass ampoules, and the need

to establish measurement traceability for

an estimated 450 radiopharmacies. NIST

is working with radiopharmacies, the FDA,

the Society of Nuclear Medicine, the

American Pharmaceutical Association,

and others to organize and implement

a program that meets these needs.

CONTACT: Dr. Brian Zimmerman

(301) 975-5191

brian.zimmerman@nist.gov

30
The second strategic element is to develop and

provide neutron standards and measurements

needed for worker protection, nuclear power,

homeland security, and fundamental applications.

Neutron Standards

and Measurements

INTENDED OUTCOME AND

BACKGROUND

The Neutron Interactions and Dosimetry

Group lias initiated a homeland-security

program to improve the ability to detect

fissile materials in transit. Working with

the Radioactivity Group, we are creating

a cargo-container inspection testbed at

NISI in order to improve our ability to test

commercially developed, homeland-security

neutron detectors. In addition to testing

detectors, the group is developing a

high-sensitivity neutron spectrometer

for detecting fissile materials in transit.

Another project with homeland-security

implications, as well as energy and environmental applications, involves imaging

chemical processes in fuel cells. Compared

to other forms of radiation, neutrons are

highly efficient in probing complex structures. This is because of their tremendous

penetration capability in almost all known

materials and their unique ability to distinguish different materials with very similar

physical properties. They are particularly

effective in detecting hydrogenous materials and light elements.

A new, neutron-imaging facility has been

constructed at the BT6, high-intensity,

thermal neutron beamline at the NIST

National Center for Neutron Research

(NCNR) nuclear reactor. The primary use

of this facility will be to non-destructively

characterize water-transport mechanisms

using real-time imaging of fuel cells.

Neutron lifetime and decay-asymmetry

experiments improve our knowledge of

the fundamental nucieon weak couplings

and may ultimately lead to a significant

test of the unitarity of the CKM matrix

for three generations of quarks. If these

measurements establish a violation of

unitarity then it will provide an important

clue to the physics beyond the Standard

Model of particle physics. The search for

a time-reversal-violating asymmetry also

probes physics beyond the Standard

Model. We operate three beams at the

NCNR to carry out such measurements.

These include a 0.5 nm monochromatic

beam, a 0.9 nm monochromatic beam

dedicated to ultracold neutron production,

and a high-intensity polychromatic beam.

The primary focus of our polarized ^He

program is the development of neutron

spin filters and application of these

devices to both neutron scattering and

fundamental neutron physics. We are

developing two optical-pumping methods, spin-exchange and metastabilityexchange, for producing the polarized

^He gas. We are pursuing applications

at the NCNR, the Intense Pulsed Neutron

Source at Argonne National Laboratory,

and the Los Alamos Neutron Science Center

The Neutron Interferometry and Optics

Facility is a national user facility operated

by the group. Radiography and tomography services and research involve academic

and industrial customers and collaborators.

During the past year, analysis of the n-H,

n-D, and n-^He scattering-length data was

completed and the time-dependent water

distribution in an operating fuel cell was

non-destructively imaged and quantified.

The success of the fuel-cell imaging drove

the development of the neutron-imaging

facility described above.

Neutron cross-section standards for key,

fundamental reactions are important

since almost all neutron cross sections are measured relative to them. Any improvement in a cross-section standard leads to improvement in all measurements that

have been or will be made relative to that

standard. We have improved neutron

cross-section standards through both

data evaluation and experimental work,

and are leading an effort that will result

in a new international evaluation of

neutron cross-section standards.

31
ACCOMPLISHMENTS

Detection of Nuclear

Materials in Transport

Spent fuel from nuclear reactors, weapons-grade plutonium, and certain

weapons-initiator materials emit large

numbers of neutrons from spontaneous

fission or (a, n) reactions. These are materials which terrorist groups could obtain

fairly easily for constructing radiationdispersal weapons or fission weapons.

Because U.S. borders are easily crossed

in many wilderness areas, and because

these materials could be obtained from

sites within the U.S., it is not sufficient

to inspect baggage and cargo at points

of entry.

Very sensitive neutron detectors coupled

with surveillance cameras could be positioned at highway chol<e points on the

outskirts of major cities or near other

sensitive locations to detect neutrons

from contraband nuclear components,

and provide warnings to security personnel to try to prevent an attack. The major

advantage of neutron detectors over

beta and gamma detectors is that the

background rates and incidences of false

positives would be much lower. There

is only a very low level of neutron background due to cosmic rays, much lower

than the natural beta/gamma background.

We are developing a very-high-sensitivity

neutron spectrometer that could be

configured for unattended, remote-sensing duty This spectrometer is based on

photon emission from recoil protons in

a liquid scintillator followed by thermal

neutron capture. It uses a segmented

geometry to improve energy resolution.

This spectrometer is based on a technique

developed for detecting background neutrons in a neutrino-detection experiment

and is expected to have sensitivity of 1 0 %

or higher. The energy resolution will be

optimized for detecting secondary fission

neutrons from "^U triggered by active

portal monitors and released through the

(y, n) reaction or fast-neutron activation.

CONTACT: Dr. David Gilliam

(301) 975-6200

david.gilliam@nist.gov

Advances in Neutron

Imaging of Fuel Cells

Neutron imaging is ideally suited for

non-destructive, in situ visualization

and quantification of water-transport

phenomena in operating, polymerelectrolyte-membrane (PEM) fuel cells.

With a prototype facility we have demonstrated that the time-dependent water

distribution in an operating fuel cell could

be non-destructively imaged and quantified. A one-second time resolution was

achieved. The total water content inside

the fuel cell as a function of time was also

quantified. The water content showed

periodic behavior with time. From timelapse images it appeared that the water

drains only when it reaches a certain volume. The periodic drainage also appeared

to be uncorrelated with the temperature

fluctuations and hydrogen-flow variations

(which were small and random, inconsistent with observed periodicity).

Less More — Attenuation —

Figure 3. Image of water transport in an

operating fuel cell obtained by neutron

transmission radiography.

Because the quantification of timedependent water distribution is a critical

tool in theoretical modeling of fuel-cell

water-transport characteristics, and

because our capabilities are unique in the

world, we have recently designed a new,

state-of-the-art neutron-imaging facility

for fuel-cell research. This facility will be

used for critical water-transport studies in

the membrane electrode assembly (MEA)

and the flow channels, for the measurements of the hydrogen-diffusion coefficient

across the MEA and water/vapor phase,

and for evaluation of the integrity of

various interfaces.

CONTACT: Dr. Muhammad Arif

(301) 975-6303

muhammad.arif@nist.gov

32
Prospects for an Improved

Measurement of the Neutron

Lifetime: Magnetic Trapping

of Ultracold Neutrons

Recent success in magnetic confinement

of ultracold neutrons in an loffe-type

superconducting magnetic trap should

lead to an improved measurement of

the neutron lifetime t^.

The trap is loaded through inelastic scattering of 0.89 nm neutrons with phonons

in superfluid ''He. Trapped neutrons are

detected when they beta decay. Energetic

decay electrons ionize helium atoms in

the superfluid, resulting in efficient conversion of electron kinetic energy into

light (scintillation). The changing rate of

neutron decays in the trap is proportional

to the number of neutrons in the trap.

To the extent that this population is

changing only by the beta-decay of the

trapped neutrons, the rate of detected

neutron decays will decrease exponentially

with a lifetime of x^,.

Figure 4. Students in Guide Hall at experiment

station for magnetic trapping of ultracold

neutrons.

The advantages of this technique over

previous experiments are: continuous

detection of scintillations from decay

electrons, and the elimination of wall

losses and betatron oscillations. Analysis

indicates that systematic errors due to

neutron losses should be controllable

to 1 0'^T„. A measurement of at the

10"^ level of statistical accuracy should

be possible, given the flux available

from the NG6 beamline at the NCNR.

CONTACT: Dr. Paul Huffman

(301) 975-6465

paul.huffman@nist.gov

Neutron Spin Filters

Based on Polarized ^He

Notable progress has been made in

developing and applying neutron spin

filters based on polarized ^He gas. We

continue to employ two optical-pumping

methods, spin-exchange and metastabilityexchange, to produce the polarized gas

for applications in both neutron scattering

and fundamental neutron physics.

Specular reflection tests using a polarized-

^He spin filter on the NCNR NG1 reflectometer were performed to compare the

use of a ^He analyzer to that of a conventional supermirror analyzer. The ^He cell was 6 cm in diameter, and the gas was

polarized to 57 % using spin-exchange

techniques. The cell was polarized off-line and used on the beamline in the absence

of optical pumping. The polarization lifetime of the cell is 550 h, which is close to

the theoretical limit set by dipole-dipole

relaxation. A compact, magneticallyshielded solenoid permitted a relaxation

time of 350 h on the NG1 instrument in

the presence of stray fields from a 0.6 T

magnet at the sample position and guide

field magnets.

The efficiency of ^He spin filters depends

strongly on the achievable ^He polarization. We have reproduced a value of

70 % polarization that the University of

Wisconsin had obtained with a unique,

optical quality, long-lifetime cell provided

by us. We have also duplicated the spectrally-narrowed, high-power diode laser

developed at Wisconsin, which has particular relevance to the size and pressure

ranges of neutron-spin-filter cells. In large

spin-filter cells, we have obtained 55 %

to 65 % 'He polarization with both

broadband lasers and the spectrally

narrowed system, but the much higher

efficiency of the narrowed system will

permit further improvement with modest

laser-power levels.

CONTACT: Dr. Alan Thompson

(301) 975-4666

alan.thompson@nist.gov

33
The third strategic element is to develop dosimetric

standards for x rays, gamma rays, and electrons

based on the SI unit, the gray, for homeland security,

medical, radiation processing, and radiation protection

applications.

Radiation Dosimetry

Standards

INTENDED OUTCOME AND

BACKGROUND

The Radiation Interactions and Dosimetry

Group promotes 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 measurement standards

for the System 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 dosimetry, rather than the

radiochromic film dosimetry originally

developed at NIST and offered here for many years as a calibration service. A new

NIST system is near completion for on- demand, Internet-based e-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 networl< of secondary

calibration laboratories.

More than 600,000 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 kVp to 300 kVp (x-ray source accelerating potential in kilovolts). These are

disseminated to manufacturers and the

medical physics community in North

America through a network of secondary

calibration laboratories. NIST maintains more than 75 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

Radiation-Sources for

Medical and Industrial

Applications

In addition to a dozen gamma-ray (^"Co

and ^^^Cs) sources and five x-ray ranges,

NIST maintains the Medical Industrial

Radiation Facility (MIRF), along with a 4 MeV Van de Graff and a 500 keV electrostatic accelerator. These are used in a

variety of radiation applications, such as

material modification, radiation-hardness

testing, electron- and bremsstrahlungbeam dosimetry, and high-energy

computed tomography development.

Design and construction are underway on two new accelerator facilities. Installation

is being completed of a 6 MeV to 20

MeV electron-beam (6 MV and 18 MV

bremsstrahlung-beam) linear accelerator

34
to support the development of direct,

therapy-level dosimetry calibrations.

Planning is also underway for a 10 MeV,

17 kW electron linac to support the standards and calibrations program for industrial radiation processing and the study

of radiation effects in materials.

CONTACT: Dr. Fred Bateman

(301) 975-5580

fred.bateman@nist.gov

Assistance to U.S. Postal

Service in Decontamination

of IVIail

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 highlyvariable mail and parcel stream.

Figure 5. NIST test packages to validate radiation doses needed to decontaminate parcels

for U.S. Postal Service.

Figure 6. Dose distribution of

sample of irradiated mail.

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 Seltzer

(301) 975-5552

stephen.seltzer@nist.gov

High-Energy Computed

Tomography (HECT) Facility

The 7 MeV to 32 MeV Saggataire linac

in the NIST Medical Industrial Radiation

Facility (MIRF) offers unique possibilities

as an x-ray source for a high-energy

computed tomography 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 may 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 Sparrow

(301) 975-5578

julian.sparrow@nist.gov

35
GOAL: TO PROVIDE

THE FOUNDATION OF

FREQUENCY MEASUREMENT!

AND CIVIL TIMEKEEPING

FOR OUR NATION.

TIME AND FREQUENCY DIVISION

The strategy of the Time and Frequency Division js to advance nrleasurennent science and to

provide time and frequency standards and measurement services to commerce and industry.

The first strategic focus is to develop the standards

that serve as reference for time-and-frequency services

and research on advanced measurement systems.

Time and Frequency

Standards

INTENDED OUTCOME AND

BACKGROUND

The intended outcome of this program

is the continuous operation of frequency

and time standards with the accuracy and

stability essential for supporting U.S. commerce and trade. This includes coordinating our activities with those of other

national standards laboratories.

The NIST time scale provides accurate

time-and-frequency reference for our

services and for research on new standards and measurement methods. It is

an ensemble of commercial cesium-beam

standards and hydrogen masers, combined

under computer control. We are advancing the performance of the time scale by

acquiring more stable clocks and improving the electronic systems that read the

clock outputs. Such improvements are

critical to the successful evaluation and

use of the next generation of primary

frequency standards.

The accuracy of the NIST time scale is

derived from the current primary frequency

standard, NIST-F1, a cesium-fountain

standard with a relative frequency uncertainty of 1 fHz/Hz. The Division plans

to build an improved cesium-fountain

frequency standard in the near future,

designed so as to simplify the process

of accuracy evaluation.

Since the accuracy of frequency standards has improved by more than an

order-of-magnitude every decade since

1950, and practical applications have

historically always followed these advances, an aggressive program of research

and development in this area is easily

justifiable. The Division is developing

frequency standards based on optical

transitions that have dramatically higher

Q factors. These optical standards already

provide much higher stability and promise

orders of magnitude improvement in

accuracy They would not have been

practical choices, however, without the

recent development of extremely stable

laser oscillators and the means for directly

connecting their optical outputs to

microwave frequencies.

Since the world operates on a unified

time system. Coordinated Universal

Time (UTC), highly accurate time transfer

(to coordinate time internationally) is a

critical ingredient in standards operations.

To achieve this coordination, the Division

is developing and using several satellitetransfer techniques.

4

36
ACCOMPLISHMENTS

Improved Steering of

UTC(NIST) to UTC

The process of running a national tinne

scale involves periodically steering it

to the international average, that is, to

UTC. Since UTC is formed by averaging

clock data submitted by many institutions,

this BIPM-generated paper average, delivered on a monthly schedule to all laboratories, represents the performance of the

time scale at past times. In fact, for a given

monthly report, the most recent BIPM data

are at least two weeks old. Each laboratory

must have a strategy for accomplishing

this steering.

Until recently, NIST opted to place

maximum emphasis on frequency stability

BIPM data arriving mid-month were

analyzed, and a fixed steering rate was

determined for the following month.

For example, the decision might have

been made to add (or to subtract) 1 ns

per day to (from) the scale for the following month. A decade ago, the noise on

UTC(NIST) and UTC made it difficult to

steer more carefully than this.

Stimulated by the acquisition of five

hydrogen masers over the last decade

and the development of a more accurate

primary frequency standard, NIST-F1 , we

investigated other steering algorithms.

Using old clock data, we found that

improved time-offset performance could

be achieved by increasing the number of

steers to two each month and by modifying the objectives of the steering. The

philosophy for steering was changed from

an emphasis on frequency stability only

to one in which frequency stability could

be degraded slightly to achieve smaller

time offsets.

The result is that UTC(NIST) now typically

deviates from UTC by no more than

20 ns, an improvement of better than

a factor of two.

CONTACT: Dr. Judah Levine

(303) 497-3903

jlevine@boulder.nist.gov

Reproducibility of Optical

Frequency

The mercury-ion optical-frequency standard has the potential for an accuracy

surpassing that of the cesium-fountain

standard by two or more orders of

magnitude. With a Q factor greater than

10'" and a transition that is relatively

insensitive to environmental factors, the

potential uncertainty for the standard is

as small as 1 aHz/Hz (0.001 fHz/Hz).

The reproducibility of this standard relative

to the present cesium standard (NIST-F1) was studied over a two-year period.

Measurements were referenced to NIST-F1

through the intermediary of a hydrogen

maser. The short-term stability of the

mercury standard is superior to that of

NIST-F1, so the maser played a key role

in the comparisons.

The variation in the frequency of the S-D

optical transition relative to NIST-F1 was

found to be less than ± 1 0 f Hz/Hz over the

two years.

F-Y 1-7

4- . 1 , 1 , 1

Figure 1. Judah Levine and Tom Parker

discussing strategies for time-scale steering.

Aug 00 Feb 01 Aug 01 Feb 02 Aug 02 Measurement Da te

Figure 2. Measurements over two years of the

frequency of the mercury optical standard relative to the cesium primary frequency standard.

The uncertainty of the absolute measure- ment (at this same level) is the most accurate measurement ever made of an optical

frequency and a very encouraging result,

since no significant effort had been made

to control systematic frequency shifts. The

largest of these shifts is expected to be the

atomic quadrupole shift, which depends

on the ohentation of the applied magnetic

field relative to ambient, static electric-field

gradients. Concepts for determining and

controlling this and other smaller shifts

have been developed, but further studies

are needed to test them.

CONTACT: Dr. James Bergquist

(303) 497-5459

berky@boulder.nist.gov

37
Improved Calcium

Frequency Standard

Because the Doppler-cooling limit for

calcium is 2 mK, the uncertainty in

frequency measurements of the 657 nm

transition are limited at about 10 Hz by

the residual motions of the atoms. Thus,

second-stage cooling is needed to improve

this as an optical-frequency standard.

Last year, we reported a concept for

achieving sub-Doppler cooling, called quenched narrow-line laser cooling

(QNLC), and demonstrated it in one

dimension. This year, we extended

our system to three dimensions.

The three-dimensional cooling relies on

the same basic principal, but uses simultaneous rather than sequential excitation

for the three-level system (clock and

quenching transitions). A frequencydoubled diode-laser system generates

the light at 423 nm used for Doppler

cooling. The second-stage cooling

requires an additional beam at 552 nm

for the quenching transitions.

With these methods we reduced the aver- age atom velocity by a factor of 1 5 and

lowered the atom temperature to 10 pK.

At this temperature, the frequency shifts due to motional effects are < 1 Hz at the

clock transition, 456 THz. Further improvements should reduce the frequency uncertainty due to motions to < 0.4 Hz, which

corresponds to a relative uncertainty of

less than 1 fHz/Hz.

Having achieved 10 pK, we turned off

the three-dimensional cooling lasers and

reapplied a pulsed version of one-dimensional QNLC cooling to the already-cooled

atoms. This reduced the temperature even

lower, to 300 nK. This suggests that even

further cooling is possible and that the

calcium optical-frequency standard has

much greater potential than previously

recognized.

CONTACT: Dr Chris Gates

(303) 497-7654

oates@boulder.nist.gov Figure 3. The calcium optical-frequency

standard being adjusted by Chris Oates.

The second strategic focus is to develop and operate

the frequency and time services essential for synchronizing important industrial/commercial operations and

supporting trade and commerce.

Time and Frequency

Services

INTENDED OUTCOME AND

BACKGROUND

The intended outcome of this program is

the reliable delivery of frequency-reference

and time-reference signals to the United

States to support industry, trade, science,

and the general public. The telephone

system, the Internet, radio broadcasts,

and satellites are all used to deliver these

signals. We serve a broad range of systems

in business, telecommunications, science,

transportation, and radio/TV broadcasting.

The Division provides timing broadcasts

from stations WWV and WWVB in Fort

Collins, Colorado, and from WWVH in

Hawaii. WWVB has a broadcast power

of 50 kW. It is substantially more useful

for mobile and consumer applications

because the antenna/receiver cost and

size are very small.

We also operate telephone-based and

Internet-based time services. We provide

a telephone audio service and a modembased Automated Computer Time Service

(ACTS). On the Internet, our 14 servers

at 1 1 sites respond to all three common

transaction protocols. Usage now exceeds one billion transactions daily.

38
Industrial calibration laboratories are

served by the Division's Frequency

Measurement Service, a system that provides these laboratories with continuous

assurance of the accuracy of their

frequency measurements. The most

demanding applications are served by the

Division's Global Time Service, which uses GPS common-view time transfer to deliver

to the user's site a timing reference close

in accuracy to that of the NIST time scale.

To enhance U.S. expertise in this field,

the Division offers a variety of training

courses. A3'/2 day metrology seminar is

offered annually, and we co-sponsor an

annual workshop on synchronization in

telecommunications systems. Additionally,

NIST staff members teach courses at

conferences.

ACCOMPLISHMENTS

NIST Internet Time Service

This service continues to grow rapidly and

is approaching a usage level of 1 billion

hits per day. Downloads of the instruction

files for setting up a users' computer are

averaging 100,000 per month. Conservative estimates of the total number of

users range as high as 50 million.

Efforts continue toward finding ways in which this service might be operated commercially. However, the lack of a means

for efficiently collecting service fees for

delivery of a few bytes of transmission

serves as a stumbling block.

9/1998 9/1999 9/2000 9/2001 9/2002

Sample Date

Figure 4. Growth in use of the NIST Internet

Tinne Service.

To deal with this continued growth, we

initiated two new projects this year. The

first involves the use of switches (routers)

that will be used to load-balance among

the 14 time servers, since some servers

are near saturation while others are experiencing only modest use. Four switches were purchased and successfully tested. They will be installed soon.

The second project, which is only now

getting started, is to implement an

encrypted time-delivery system through one or more of the servers, using a

concept we developed and patented.

The objective is to provide the means

for secure delivery of time signals to

systems operated by industry.

The hope is that there will be a gradual

grov\/th of commercial delivery of time

signals by companies that are targeting

specific market sectors. At this point, we

are working with several companies that

are interested in delivering time services

to financial traders.

CONTACT: Dr. Judah Levine

(303) 497-3903

jlevine@boulder.nist.gov

WWVB Time Broadcasts

Recognizing that there has been a tremendous expansion in the number of consumer products based on the WWVB

time broadcasts, we made a variety of

improvements to the broadcast systems

during the last year. These were made

as part of a long-term plan to assure

continuity of operation of this service.

New insulators were installed at the

ground level of all of the guy wires

supporting the eight antenna towers.

These insulators are designed to be failsafe and retain their mechanical integrity

even if the insulator should break. This

will prevent the sort of tower damage

experienced several years ago when one

of the guy-wire supports failed completely

due to an insulator failure. These caused

substantial damage to the tower.

A secure climbing line was added to

each of the 1 20 m towers to comply with

OSHA tower-safety requirements. Not

only will this assure climbing safety,

but it will also speed maintenance and

repair activities.

39
The old tower beacons were replaced

with new FAA-approved beacons to

improve the visibility of the beacons to

low-flying aircraft. We plan to repaint the

towers in the FAA-approved manner to

assure good visibility to aircraft during

daylight hours.

Figure 5. An aerial view of the WWVB

antenna systems.

Finally, we designed a field-strength meter

for the 60 kHz signal and contracted to

have a number of these produced for field

monitoring purposes. These will be placed

at various locations around the country

to continuously monitor signal strength.

The field-strength information will be fed

periodically to the station website for use

by WWVB product manufacturers and

their their customers.

CONTACT: Mr. John Lowe

(303) 497-5453

lowe@boulder.nist.gov

The third strategic focus is to develop new measurement systems and methods in support of emerging

technologies.

New Measurement

Systems and Methods

INTENDED OUTCOME AND

BACKGROUND

Through this program, the Division

prepares for the future of time-andfrequency measurements and calibrations. Through interactions and discussions with

NIST constituents, we identify important,

emerging industrial requirements and

technologies, and develop measurement

systems and methods designed to meet

their needs.

NIST has a long history of metrology

expertise and leadership in such areas as:

the non-stationary statistics of clocks and

oscillators; optical-frequency measurement

systems; atomic and optical oscillators;

time-and-frequency transfer through

satellites; low-phase-noise electronics; and network synchronization. The ultimate

goal is to apply our expertise to carefully

selected projects so as to assure continuity

in providing the highest-performance timeand-frequency services to U.S. industry,

science, and the general public.

The synthesis and measurement of optical

frequencies have become a central focus

in this program. The new optical-frequency combs generated by femtosecond

lasers have provided the means for measuring optical frequencies at uncertainty

levels orders-of-magnitude better than

could be done previously Such measure- ments will clearly have impact on wavelength standards for fiber communications

systems and on absolute length metrology

These same combs are being used to

generate microwave outputs from opticalfrequency standards, essentially providing

the basis for a whole new generation of

atomic standards. Now that the accuracy

of these measurement systems has been

established, work involves simplification

and noise reduction.

Another component of this program

is the measurement of close-to-carrier

noise in oscillators and other electronic

components. A closely related effort

involves improving statistical metrics

for analyzing such noise. Projects in

this area will have impact not only on

improvements in characterization of clocks

and oscillators, but also in telecommunications systems, advanced radars, and

other narrow-band electronic systems.

Finally, smaller, less-accurate oscillators

play a major role in a variety of measure- ment instruments and electronic systems.

We have often contributed to developing and improving such oscillators. The

newest program in this area, stimulated

in large part by some of our fundamental

research, is a DARPA-funded program

to develop a chip-scale atomic clock, a

program involving NIST, several universities,

and a number of companies.

40
ACCOMPLISHMENTS

Improved Frequency-Comb

Generator

One of the key stability/reliability issues

with the usual frequency-comb generator

involves the microstructure optical fiber

used to broaden the output of the

femtosecond laser to a full octave. The

very high power density required to

achieve this broadening causes damage

to the fiber. It must be adjusted and

replaced periodically

We recently collaborated with the Institut

fur Halbleitertechnik (Germany) to demonstrate a phase-coherent link from optical

to microwave frequencies in a system that

does not require a microstructure fiber

for spectrum broadening. This success is

based on the use of a 1 GHz repetitionrate, mode-locked laser and the application of a scheme that requires coverage of

only of an octave. In this self-referencing

scheme, the 2"'' and 3'''' harmonics of the

optical signal of interest are heterodyned

with elements of the frequency comb to

ultimately lock the 1 GHz repetition rate

of the mode-locked laser to the optical

signal. While our new 1 GHz femtosecond

laser just generates a full octave, further

development will be needed to allow

reliable locking using only the fundamental

and 2"'' harmonic of the optical signal.

The immediate consequence of this devel- opment is to increase the uninterrupted,

microwave-frequency output, self-referenced

to an optical transition, from tens of minutes

to about a day Such improvement in

reliability is essential to the future of opticalfrequency standards, since, ultimately

such standards will have to operate

unattended for long periods. In the

experiments on this new system, the

microwave output frequency from a comb

that was phase-locked to a calcium opticalfrequency standard (456 THz) was shown

to have a short-term frequency stability

100 times better than that of a hydrogen

maser. The long-term performance of the

device will depend on how well systematic

effects in the optical standard are controlled.

CONTACT: Dr. Scott Diddams

(303) 497-7459

sdiddams@boulder.nist.gov

Statistical Measure for

Long-Term Stability

The measurement of the long-term

stability of clocks and oscillators has been

a long-standing problem for science and

industry. The Allan deviation and another

statistic, total deviation, both require data

acquisition over twice the period of the

desired averaging interval. For example, to

determine the stability at 1 month would

require a two-month-long data run.

Recently, we developed a new statistic

that yields a measure of stability at the

end-point of the data sehes. The most

significant effect of this advance is to cut

required measurement times in half, thus

substantially cutting the cost of acquiring

the most expensive data point.

Moreover, the statistic not only retains

all of the desirable features of the Allan

deviation, it has fewer intrinsic biases and

much narrower confidence limits. We

found that a more complex combination

of frequency sums and differences could

yield an Allan-like statistic clear out to

the interval of the data run itself.

As a test, the statistic was used over

the past two years for measuhng the

performance of the NIST time scale and

the primary cesium-fountain frequency

standard, NIST-Fl.

The results clearly demonstrated the

efficiency of the statistic. It served to

improve the performance of the time

scale and to reduce the time required

to evaluate the accuracy of NIST-Fl

.

CONTACT: Dr. David Howe

(303) 497-3277

dhowe@boulder.nist.gov

Broadly Tunable Microwave

Reference Oscillator

The measurement of phase-modulation

(PM) noise and amplitude-modulation

(AM) noise of clocks and oscillators

presumes the availability of stable reference oscillators at the desired measure- ment frequencies. However, it is too

expensive and cumbersome to maintain

dedicated reference oscillators for each

measurement frequency To date, methods

for synthesizing offsets from stable, fixedfrequency oscillators have been extremely

complex. The problem is that frequencyoffset synthesis generally creates

unacceptable levels of noise.

We recently developed a simple referenceoscillator system with broad tunability

but without much of a noise penalty In

the traditional approach, a synthesized

offset is added to a stabilized oscillator

Therefore, the noises of these two signal

are independent and additive.

41
The innovation of the new system is in

the placement of the offset synthesizer

inside a servo control loop used to stabilize a high-Q microwave cavity. The frequencies of two oscillators, the reference

signal and the offset, must add up to the

fixed resonance frequency of the cavity

Therefore, the reference-signal frequency

will be changed in a direction opposite to

changes in the synthesized offset frequency.

The system suppresses the total noise on

the reference signal.

Figure 6. David Howe and Craig Nelson with

the microwave cavity used to suppress noise

in their new reference oscillator

The concept was experimentally demonstrated using a high-Q microwave cavity

with a resonance frequency of 10.6 GHz,

a dielectric resonant oscillator, and a

digital offset-frequency synthesizer. The

results demonstrated the addition of

tunability without substantially adding to

the noise. This development advances the

art of PM and AM noise measurement.

CONTACT: Dr. David Howe

(303) 497-3277

dhowe@bouldernist.gov

Chip-Scale Atomic Clock

Earlier fundamental research at NI5T on

a very small atomic clock, based on the

concept of coherent population trapping,

has served to focus broader interest on

the subject of miniaturization. In fact, a new DARPA-funded program was stimulated by a NIST-hosted workshop held 1 'A

years ago in Boulder. The advantage of

the coherent-population-trapping concept

is that the traditional microwave cavity is

eliminated. The need for a microwave cavity

has long been an impediment to miniaturization below the few-centimeter level.

We are now collaborating with a group

of eight companies and universities, also

funded by DARPA, on developing a chipscale atomic clock. Because of our expertise

in miniaturizing atomic clocks, we will

study basic aspects of miniature atomic

clocks to help guide developments on

this aspect of the program. Success in this

endeavor could have impact on military

systems, particularly GPS, and civilian

technology such as wireless telephony.

We are focusing on several projects.

The first involves characterizing miniature

vapor cells, both wall-coated and buffergas-filled cells. One of the objectives will

be to experimentally establish the scaling

(size) laws, thus defining the limits for

miniaturization. We are also supporting

studies at the University of Colorado

of the cell-wall coatings deemed to be

essential to miniaturization to the submillimeter level. An auxiliary study, being

performed collaboratively with NIST EEEL

staff, is to examine the potential of direct

interaction between magnetically coated

MEMS oscillators and atoms. Success in

this experiment could provide a dramatically simpler approach to miniaturizing

atomic clocks and atomic magnetometers.

CONTACT: Dr. John Kitching

(303) 497-4083

kitching@boulder.nist.gov

The fourth strategic focus is to develop quantumlogic components and quantum-information systems

based on trapped ions, in support of new atomic frequency

standards and a national program aimed at advancing

computation and communication.

Quantum-Information

Processing Using

Trapped Ions

INTENDED OUTCOME AND

BACKGROUND

The intended outcome of this program

is the development and demonstration

of prototype logic circuits that can serve

as the basis for quantum computation,

quantum measurement, and noise

reduction in atomic clocks.

The current program grew out of a NIST

competence project to reduce fundamental,

quantum-projection noise in multi-ion

atomic clocks. The realization that the same trapped-ion systems could also be

used for quantum information processing

42
generated substantial outside interest. As

a result, the ion progrann expanded and

its success stimulated the development

of other quantum-computation and

quantum-communication programs at

NISI Today, the ion quantum-information

project represents only a portion of a NIST

centrally coordinated effort that now has

fairly broad objectives.

There are several strong motivations for

this work. From a national perspective,

developing a quantum computer, while an

extremely challenging undertaking, would

have a major impact. This arises from the

fact that a quantum computer should be

able to perform certain functions exponentially faster than even the largest array

of conventional computers. As examples,

a quantum computer could much more

efficiently factor large numbers, a process

that is at the heart of decryption, and it

could greatly speed database searches.

The second broad motivation is the

expected impact on measurement science.

The ability to produce and manipulate

arbitrary states of single atoms and

collections of atoms has clear implications

for measurement science and for atomic

clocks in particular. Last year, we demonstrated noise reduction below the standard

quantum limit for two entangled ions,

and implied that these methods can be

extended to many ions, providing for

increased performance in atomic clocks. More generally, the ability to engineer

quantum states at the single- and fewatom level has implications for metrology

in nanoscale systems.

ACCOMPLISHMENTS

Geometrical-Phase

Quantum-Logic Gate

The recent demonstration of a novel,

two-qubit, geometrical-phase quantumlogic gate significantly advances prospects

for quantum computation. This new gate

appears to have features that overcome

a number of difficulties identified earlier.

In this device, rather than manipulating

the direction of the spin states, we control

the phases of the spin states using optical

dipole forces. The greatest advantage of

this change is that the requirements on

control of the phase of the probe laser are

dramatically reduced. For gates of the sort we demonstrated and reported two years

ago in Nature, the laser phase had to be

kept constant throughout the full, coherent sequence of operations on the entire

set of qubits involved in the system. For

the new gate, the laser phase has to be

well controlled only during a single-gate

operation. This is dramatically easier to do.

The geometrical-phase gate also shares

many of the positive attributes of the

earlier gate. It is a one-step gate. All of

the qubits involved can be placed into

proper states at the same time. Also,

individual-ion addressing is not required.

In fact, the ions are best illuminated simultaneously This means that careful laser

focusing is not needed. Finally, motional

eigenstates are not required as long as the

ions are tightly contained and within the

Lamb-Dicke limit.

The new gate is particularly well suited

to application in multiplexed trap systems,

a design approach that will provide for

scaling to larger logic systems. For example,

there is no requirement for maintaining

equal laser couplings to each ion as in the

previous, two-qubit gate. This means that

sympathetic cooling can be used in more

complex systems without introducing

difficulties in maintaining specific laser- beam couplings to the ions. In addition, in

contrast with the practical realization of

other gates, the phases imposed on qubits

can be generated with co-propagating

Raman laser beams. This means that the

qubit phases will be highly immune from

displacement between the ions and the

laser beams. Thus, motions (vibrations) of

the trap relative to the laser beams will

cause fewer problems.

CONTACT: Dr. David Wineland

(303) 497-5286

wineland@boulder.nist.gov

Figure 7. David Wineland adjusting one of the

systems used for studying quantum-logic gates.

43
GOAL: TO PROVIDE FUNDAMENTAL UNDERSTANDINGS OF.

NANO-, BIO-, AND QUANTUM

OPTICAL SYSTEMS IN PARTNERSHIP WITH THE UNIVERSITY

OF COLORADO AT JILA. QUANTUM PHYSICS DIVISION

The strategy of the Quantum Physics Division is to help produce a new generation of scientists and to investi

gate new ways of directing and controlling atoms and molecules, measuring-chemical and biological processes

and their interactions with nanostructures, and exploiting interactions of ultrashort light pulses with matter.

J

The first strategic element is to develop the

laser as a precise measurement tool.

Laser Research

INTENDED OUTCOME AND

BACKGROUND

Laser capabilities today are used for a wide variety of industrial and scientific

purposes, ranging from providing the

length scale for mechanical measurements

to providing a means to directly connect

the optical- and microwave-frequency

domains. The Quantum Physics Division

continues a leadership role in these fields,

developing new techniques vis-a-vis

precision lasers and their applications.

In laser research, various schemes are

explored for stabilizing lasers and for using

them as frequency standards. Recent work

of the Division addresses the creation,

utilization, and study of ultrafast laser pulses,

which can be applied both to produce

and control wave packets and to study

nonlinear optical-wave interactions. The

evanescent-wave property of light has

been exploited to guide atoms through

hollow fibers and prevent them from

touching the sides. The Division has a

rapidly developing research program in

ultrafast phase-control and frequency

measurements, which are applied to

control atomic and molecular dynamics,

as well as to access wholly new types

of frequency and length standards.

One of our senior scientists, Jan Hall

(one of JILA's original scientists), is widely

acknowledged to be the "father" of

much of the laser stabilization and associated precision-measurement methods that

are used today by NIST, the international

standards community, and leading universities throughout the world. Our recent

hires serve to further strengthen this

activity and to assure NIST of a continuing

world-leadership position in this critical

standards and measurement domain.

ACCOMPLISHMENTS

Precision Spectroscopy of

Cold Atoms and Molecules

We have extended the coverage of

iodine-based, optical-frequency standards

toward the shorter wavelength region,

from 532 nm to 500 nm. Owing to the

attractive properties of newly discovered

resonances, namely narrow linewidth and

high signal-to-noise ratio, we are developing a new generation of cell-based opticalfrequency standards with instability less

than 10 f Hz/Hz at 1 s averaging time. We

have made absolute frequency measure- ments on several of these transitions

using the JILA-developed, femtosecond,

frequency-comb technology We have also

discovered new and interesting changes in

the hyperfine interactions of the iodine

molecules when the transitions approach

the dissociation limit in the excited state.

Broadband, femtosecond lasers and ultrahigh-resolution spectroscopy have been

linked in experiments on laser-cooled

rubidium (Rb) atoms. A phase-coherent,

wide-bandwidth optical comb was used

to induce multi-path quantum interference for the resonantly enhanced, two44
photon transition in cold Rb atoms. We

have also dennonstrated the possibility of

using cold atonns to control both degrees

of freedom for the femtosecond-laser

system, namely the comb spacing and

the carrier-offset frequency.

Working with the trap dynamics of lasercooled, alkaline earth, ^^Sr atoms, we

have established the first rigorous test of

Doppler-cooling theory in a strictly twolevel atomic system. We have also, for

the first time, magnetically trapped the

*^Sr atoms in their long-lived, metastable

states, paving the way for a possible evaporative-cooling route toward quantum

degeneracy of the alkaline-earth atoms.

Furthermore, we demonstrated the existence of a sub-Doppler cooling mechanism for the fermionic isotope ^^Sr using

its nuclear magnetic substructure. ^'Sr has

been identified as the best candidate for

an ultimate optical-frequency standard

based on cold neutral atoms, due to the

existence of an electromagnetic-fieldinsensitive, narrow, forbidden transition

from 'So to 'Pq.

Our cold molecule "machine" has started

to produce results. The goal of this project

is to explore control techniques on molecules similar to those applied to atoms.

We have successfully produced rotationand vibration-cooled OH radicals from a

pulsed, supersonic beam source. These

polar molecules can then be guided

downstream using high-voltage, electrostatic fields that can be switched to slow

down the translation velocity. We will

eventually trap the cold molecules in an

electrostatic trap and perform the first

OH cold collisions with a controlled

magnetic field. We believe these kinds

of experiments will mark a new era in

physical chemistry.

CONTACT: Dr. Jun Ye

(303) 735-3171

ye@jila.colorado.edu

Precision Frequency

Metrology and Ultrafast

Science

By achieving the first experimental

demonstration of tight synchronization

and controlled phase coherence between

independent femtosecond (fs) lasers, we

have opened up a new sub-field in ultrafast science. The following is a list of

novel experiments performed in the

laboratory in the past year.

(1) Sub-femtosecond ultrafast laser

synchronization. The ultimate goal of

this research is to develop an arbitrary

lightwave generator. To do this, one must

have a timing jitter below the opticalcarrier period. For 800 nm, this is 2.7 fs. We implemented a wide-bandwidth servo

loop to synchronize two independent

mode-locked lasers on a sub-femtosecond

time scale, with 1 ms averaging. Even

with a detection bandwidth above 2 MHz,

we still see a timing jitter of under 2 fs.

This is the lowest timing jitter ever reported

using an active-synchronization scheme,

and even passive techniques have not

been shown to be any better.

There are many benefits of using active

synchronization (as opposed to passive).

For example, we can arbitrarily set the

time delay between the two pulse trains

to any value we choose, with femtosecond-level precision. We have already

demonstrated all-electronic, precision

switching between two time delays, with

high speed and no hysteresis. In principle,

our active-synchronization technique could

lock together as many different lasers

with different gain media as desired.

(2) Nonlinear imaging for biological

applications. We have reported another

significant breakthrough in ultrafast technology that has potentially a wide range

of applications. We apply our synchronization technique to coherent anti-Stokes

Raman scattering (CARS) spectroscopy, one of the most powerful methods for

acquiring chemically-selective maps of

biological samples. With the availability

of tight synchronization, we can now utilize two independent picosecond (ps) lasers,

with great flexibility of wavelength tuning

and pump-power manipulation. We have

shown that technical noise associated

with timing jitter can be completely eliminated from the CARS signal, and we have

recorded CARS vibrational images of living

cells and polymer beads with significantly

improved quality. This new technical capability will be of great interest to chemists,

materials scientists, and biophysicists.

(3) Arbitrary wavelength/spectrum

generation. We have demonstrated a new experimental approach for flexible femtosecond pulse generation in the midIR, using difference-frequency-generation

from independent Ti:sapphire (Ti:S) lasers.

This work represents a significant step

towards realizing an ideal light source for

coherent control of molecular vibrations

in the mid-IR region.

45
The resultant mid-IR pulse train can be

easily tuned, with an adjustable repetition

frequency up to 100 MHz. Arbitrary,

rapid switching of the generated wavelength and progrannnnable amplitude

modulation are achieved via precision

setting of the time delay between two

ohginal pulses. The average power of

the pulses exceeds 1 5 pW, which to our knowledge represents the highest power

in the > 7.5 (jm spectral range obtained

from direct difference-frequency-generation

of Ti:S pulses.

(4) Optical frequency metrology.

Having demonstrated last year the first

optical atomic clock, we have now

improved its simplicity and reliability The

optical atomic clock offers unprecedented

short-term stability and will provide better

long-term stability as well. We note that

our progress has been acknowledged with

a large MURI contract from the Office of

Naval Research, with JILA as the center

of this multi-university research project.

Comparison and dissemination of the

optical-frequency standards and atomicclock signals have now become an urgent

need. We have carried out work in transmitting and comparing highly stable rf- and optical-frequency standards using two

dark fibers already installed in the Boulder

Research and Administrative Network

(BRAN). The optical link between our labs

at JILA and NIST Boulder is 6.9 km long,

roundtrip. A hydrogen-maser-based rf

standard with an instability of = 240

fHz/Hz at 1 s is transferred from NIST to

JILA via this link. This maser-based rf reference, about ten times more stable than

our commercial, cesium atomic clock, is

used as the time base for femtosecondlaser-based optical combs used for

absolute optical-frequency measurements.

The maser-based signal is also used to make direct comparisons against the output of an optical clock, i.e., the repetition

frequency of the femtosecond comb stabilized by an optical transition. This opticalfrequency standard is based on an iodinestabilized Nd:YAG laser at 1 064 nm with

an instability of = 40 fHz/Hz at 1 s, which

is transferred from JILA to NIST using the

second fiber. With independent femtosecond frequency combs operating in both

laboratories, the absolute optical frequency

can be measured simultaneously with

reference to the common maser-based

rf standard.

A direct optical-frequency comparison

enabled by the fiber link was also carried

out, with results that are clearly superior

to the rf-based measurements. We measured the degradation of the optical and

rf standards due to the instability in the

transmission channel and developed

methods for active frequency-noise cancellation over the 6.9 km roundtrip distance. Optical-frequency transfer instability

between JILA and NIST through the BRAN

fiber is now about 3 fHz/Hz at 1 s after

noise cancellation. A unique aspect of the

optical phase-noise compensation is that

the transit time of the optical link

is comparable to the coherence time

of the laser, leading to interesting coherence effects.

CONTACT: Dr. Jun Ye

(303) 735-3171

ye@jila.colorado.edu

Progress In Cell-Based

Optical-Frequency Standards

With the recent breakthrough in opticalfrequency measurements using fs-laser comb technology, it is clear that optically

based frequency standards will play a

decisive role in future frequency standards

and applications. Right now, the NIST

program in ion-trap systems is the world

leader. However, gas-cell approaches

appear capable of providing comparable

stability at vastly less cost and in more

compact space, although with somewhat

less accuracy potential.

Accordingly, we have developed a full

theory of the limits achievable with compact, gas-cell-based, optical-frequency

standards. This shows that another factorof-ten improvement should be possible on our iodine-based system, which has

already been shown to be more stable

than other available frequency sources

including the NIST H-maser—for times less

than a few hundred seconds. Use of a still more favorable transition should provide

another five-fold gain. Another major

advance likely to improve the long-term

stability is in the technology of distortionfree modulation, where we recently

demonstrated that fringing fields in the

Electro-Optic Modulator (EOM) could

be controlled.

CONTACT: Dr. John L. Hall

(303) 492-3126

jhall@jila.colorado.edu

46
Phase Control of Ultrashort

Optical Pulses

During the last few years, there has been

a remarkable convergence between the

technology of ultrafast lasers and that

used to stabilize single-frequency cw

lasers. This has led to significant advances

in the fields of optical-frequency metrology

and optical atomic clocks. It also promises

to have a large impact on ultrafast science

by making it possible to control the carrier-envelope phase of ultrashort pulses.

Control of the carrier-envelope phase

will allow arbitrary electronic waveforms

(as opposed to intensity waveforms) to be

synthesized at optical frequencies. Such

electronic-waveform synthesis will be

useful in signal-processing applications,

in coherent control of quantum processes,

and in extremely nonlinear optics.

Before these avenues can be explored,

a train of optical pulses with identical

carrier-envelope phase must be generated,

i.e., the carrier-envelope phase coherence

must be preserved for times longer than

it takes to perform an experiment. The

carrier-envelope phase evolution in the

pulse train emitted by a mode-locked

laser is manifest as an offset frequency, /o,

in its spectral comb, with carrier-envelope

phase fluctuations causing the spectrum of

/o to broaden.

Recent results show that, with optimization of the stabilization, the linewidth of

/o can be below 1 MHz, corresponding to

a carrier-envelope phase coherence time

of hundreds of seconds.

CONTACT: Dr. Steven Cundiff

(303) 492-7858

cundiffs@jila.colorado.edu

Spin Coherence in A/-Doped

Semiconductors.

The possibility of using the spin degreeof-freedom of electrons for encoding

information has recently attracted significant attention. Proposed implementations

include devices analogous to traditional

microelectronic devices and those 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. In addition, optical preparation and probing is likely to be useful

for quantum-information applications.

The observation at the University of

California (Santa Barbara) of very long

spin-coherence times in n-doped, bulk

GaAs provided significant impetus for our

research. We use the technique of Faraday

rotation to probe the spin coherence of

such systems and to study how it depends

on the density of optically excited electrons, which are initially spin polarized.

We have shown that the spin-coherence

time decreases at high excitation density

and that the electron g-factor changes subtly The decreased spin-coherence time is

attributed to an increase in spin-spin scattering amongst the electrons. The variation

in the g-factor is presumably due to its

/c-dependence, coupled with the change

in the average k of the electrons as the

excitation density is changed. This is being

tested by examining several samples with

different doping densities. Measurement

of the /c-dependence of the g-factor is

important since it effectively broadens the

electron-spin precession, thereby decreasing the observed spin-coherence time.

Complete Measurement

of Exciton Scattering

in Quantum Wells

Many-body interactions among carriers

influence the performance of optoelectronic devices, such as laser diodes and

semiconductor optical amplifiers. Ultrafast measurements of coherent processes in

semiconductors, using techniques such as

transient four-wave-mixing (TFWM), have

proven to be very sensitive to many-body

interactions. The results of these measure- ments test the fundamental theories used

to model devices.

We are using a 3-pulse implementation

of TFWM to study excitonic scattering

processes in GaAs/AIGaAs multiple quantum wells. By using a 3-pulse configuration, we can measure decay of the

Raman-like coherence between the heavyhole and light-hole excitons. In the same

experiment, it is also possible to observe

coherences between the heavy-hole exciton and the ground state, and between

the light-hole exciton and the ground

state. By studying these simultaneously,

insight is gained into how coherence is

lost during scattering events. The relative dependence of the scattering rates on the

excitation density and sample temperature

helps distinguish carrier-carrier scattering

and phonon-carrier scattering.

CONTACT: Dr. Steven Cundiff

(303) 492-7858

cundiffs@jila.colorado.edu

CONTACT: Dr. Steven Cundiff

(303) 492-7858

cundiffs@jila.colorado.edu

47
The second strategic element is to exploit BoseEinstein condensation and quantum-degenerate Fermi

gases for metrology and ultralow-temperature physics.

Bose-Einstein and

Fermi-Dirac Gases

INTENDED OUTCOME AND

Additionally, a program to use currentcarrying wires as "pipes" to both guide

and "split" cold atoms for atom interfer- ometry is being aggressively pursued.

BACKGROUND

The Quantum Physics Division and JILA

are today a world focal point for studies

of Bose-Einstein condensates and quantum-degenerate Fermi gases. The mutual

advantage to NIST and the University of

Colorado in collaborating at JILA was

best exemplified when Eric Cornell (NIST)

and Carl Wieman (CU) together achieved

for the first time a Bose-Einstein condensate, and for that accomplishment were awarded the 2001 Nobel Prize in Physics.

Coupled with the creation of the first

quantum-degenerate Fermi gas by

Deborah Jin (NIST) and one of her CU

graduate students, Brian DeMarco, this

places the Quantum Physics Division and

JILA at the forefront of studies of macroscopic—and therefore easily studied

quantum-mechanical systems.

A better understanding of these systems

is critical today because the miniaturization of electronic components is pushing

into the size region where quantummechanical effects play a significant role

in their operation. We plan to continue

to explore and exploit the new quantummechanical systems that these discovehes

have made accessible, and maintain our

leadership position.

ACCOMPLISHMENTS

Frequency Shift Metrology

We are in the midst of a series of studies

to understand the microwave transition in

ultracold rubidium. Ultracold temperatures

and magnetic-trapping technology make

possible interrogation times extending to

2 s, which leads to very narrow line widths

and correspondingly higher precision.

Residual interactions between the atoms

cause shifts in the transition frequency

that must be accounted for. We can track

these small shifts with great accuracy

since the extended interrogation time

makes it possible to follow the frequency

shifts as the cloud heats, cools, decoheres,

and even undergoes a phase transition

into or out of a Bose-condensed state.

Many of the observed effects are quite

countehntuitive, and therefore help us

reshape our understanding of what it means for a sample of gas to lose its

internal coherence.

CONTACT: Dr Eric Cornell

(303) 492-6281

cornell@jila.colorado.edu

BEC on a Chip

In other cold-boson work, we have

succeeded in injecting a condensate into a

lithographically patterned microstructure,

an "atom chip." The long-term technological goal of this work is to develop

super-precise inertia! sensors, i.e., gyroscopes and gravity gradiometers. The

condensate will travel through the chip and

be coherently split and recombined. The

resulting interference signal will be exquisitely sensitive to minute inertial effects.

For now, our very preliminary condensatein-chip studies have demonstrated that

minute imperfections in the wire can have

deletehous effects on the condensate's

coherence. Our new generation chips

will be constructed with considerably more attention to this issue.

CONTACT: Dr Eric Cornell

(303) 492-6281

cornell@jila.colorado.edu

Figure 1. Eric Cornell, co-discoverer

(together with Carl Wieman) of Bose-Einstein

condensation in dilute atomic vapors.

48
"Destroying" BEC

Ironically, one of the more important scientific advances in our ultracold research

this year is progress not towards creating

a Bose-Einstein condensate but towards

destroying it. As a ball of Bose-condensed

gas starts to rotate, it becomes pierced by

progressively more, tiny tornadoes known

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 the vortices.

Theory predicts there will be a reordering

transition in which the condensate is

destroyed, to be replaced by a highly

correlated gas reminiscent of the quantum

Hall state in solids. Achieving and characterizing this transition in the lab is a prime

scientific goal, because we anticipate it

will generate important insights into

analogous transitions in technologically

important, condensed-matter systems,

including the giant-magneto-resistance

phenomenon that is so vital to progress in

disk-drive read-sensor technology. During

the year we advanced the figure-of-merit

for producing the transition a factor of

20 closer to the goal.

CONTACT: Dr. Eric Cornell

(303) 492-6281

cornell@jila.colorado.edu

Cold Fermions

We successfully implemented a number of

new experimental capabilities that

enhance our research opportunities in

exploring Fermi gases of cold atoms. We

developed a far-off-resonance, opticaldipole trap for confining fermionic atoms

in any combination of hyperfine spinstates. This trap will be used to search

for a new superfluid phase driven by

resonant interactions in the gas.

To this end, we made the first measure- ment of a magnetic-field-tunable,

Feshbach scattering resonance for fermionic atoms. This resonance allows us to

control interaction strengths and is a key

ingredient for realizing resonance superfluidity as predicted by Holland and coworkers. We have also measured the first p-wave Feshbach resonance for fermionic

atoms. This resonance occurs in the scattering of atoms in the same spin-state and

could provide a mechanism for realizing

superfluidity with p-wave Cooper pairs.

In another experiment, we demonstrated

simultaneous cooling and trapping of

Bose and Fermi gases in the quantum

regime. Bose-Einstein condensates

are produced using ^''Rb atoms. Simultaneously trapped, fermionic *°K atoms

are cooled sympathetically and reach

roughly a quarter of the Fermi temperature. Work is proceeding in characterizing

this new system.

CONTACT: Dr. Deborah Jin

(303) 492-0256

jin@jilau1 .colorado.edu

Figure 2. Deborah Jin aligns an infrared laser

for a magneto-optical trap. The trap is used

to collect 1 billion rubidium atoms under ultrahigh vacuum. The atoms are then sent to a

second trap under even higher vacuum and

cooled to 100 nanokelvin. The result is a so

called "Bose Einstein condensate" in which

a large number of atoms behave coherently.

49
The third strategic element is to investigate biological systems at the single-molecule level. With a new

thrust in biophysics, the Quantum Physics Division aims

to investigate critically important biological systems at

the single-molecule level, drawing upon our measurement

expertise and experience with atomic and quantum systems.

Biophysics

INTENDED OUTCOME AND

BACKGROUND

As JILA and the Quantum Physics Division

lool< to the future, it is clear that an

important scientific revolution is presently

taking place in the area of biophysics.

Accordingly, we are evolving a part of our

research program in this direction to help

NIST contribute to and be a meaningful

part of this scientific future.

Our strengths—namely, our ability to build

institutional bridges to university departments that are already strong in this area,

a superlative infrastructure that serves to

extend the quickness of our eyes and the

reach of our hands, our experience in

manipulating and measuring similarly

sized atomic and quantum-mechanical

systems, and a reputation that allows us

to attract and successfully hire the best

and brightest of today's young scientists

all suggest that we can hope to become

a significant contributor to this scientific

revolution. We have therefore embarked

on a program in biophysics that is to be

carried out in close collaboration with

the University of Colorado, in particular

with the Department of Molecular,

Cellular, and Developmental Biology, and

with the Biochemistry Division of the

Chemistry Department.

We expect that bridging JILA to additional

departments will enhance the very productive, interdisciplinary character of JILA. Most importantly, we expect to be able to

find a niche where, by capitalizing on our

existing expertise, we will be able to bring

this program to the same very high stature

as we have for our other programs.

This year, three research projects were

initiated, with NIST and other-agency support. They build on our fundamental laser

skills and chemical-physics experience, and

contribute as well to the rapidly evolving

NIST research programs in nanotechnology

and single-molecule biophysics.

ACCOMPLISHMENTS

Fluorescence Microscopy

Studies of Biomolecular

Conformational Dynamics

This biometrology project is based on

ultrasensitive time-, color-, and polarization-resolved fluorescence detection of

single biomolecules (specifically, dyelabeled DNA and RNA oligomers) in a highnumerical-aperture confocal microscope.

The operation of this apparatus is as

follows. A pulse train from a mode-locked

laser (532 nm, doubled Nd:YAG, 80 MHz

repetition rate) is focused into an aqueous

sample with a water-immersion microscope objective (NA = 1.3), thereby

illuminating = 0.1 femtoliter of solution.

For sufficiently dilute samples of labeled

DNA/RNA, this corresponds to less than

single-molecule occupancy in the detection region, which permits laser-induced

fluorescence from single molecules to

be unambiguously monitored.

The resulting weak fluorescence is collimated, separated from the = 10^ fold

stronger, incident laser with high-rejection

dichroic filters, sorted by both polarization

and color, and finally imaged on singlephoton-counting avalanche photodiodes.

The individual photon events are then

efficiently sorted by color and polarization

and stored as a function of time-after

the incident laser pulse. The fluorescence

dynamics of the biopolymers are then

extracted via time-correlated, singlephoton counting. This permits measure- ment of fluorescence decay rates of the

labeled DNA/RNA species, or fluorescenceresonant-energy-transfer (FRET), between

donor and acceptor dyes on a single

DNA strand.

In a complementary thrust, we are developing methods for immobilizing dyelabeled biomolecules in aqueous gels to

allow us to measure fluorescence and to

image single molecules by raster-scanning

of the laser over the sample with a precision, PZT, servo-controlled stage.

50
The combination of FRET, immobilized

labeled biomolecules, and ultrasensitive

single-molecule detection methods

offers new opportunities for directly

probing the extremely important conformational dynamics of biomolecules in

real time, e.g., folding and unfolding.

This class of information is of crucial

relevance to issues concerning RNAbased enzymes, so-called ribozymes.

CONTACT: Dr. David Nesbitt

(303) 492-8857

djn@jila.colorado.edu

Single-Biomolecule

Electrophoresis

A second new biometrology project is

single-molecule electrophoresis. The

apparatus for these studies is based on

wide-field microscopy through a thin

gel-electrophoresis cell, in which weak

electric fields (1 V/cm to 5 V/cm) are

used to coax single DNA molecules

through a = 20 |jm x 20 pm field of view.

The DNA molecular motion can be studied by labeling with highly fluorescent

dyes that are illuminated with cw 488 nm

laser excitation and detected by imaging

on an intensified, CCD camera. The

sensitivity of the method is sufficient to image at a 10 Hz frame-repetition rate.

This permits monitoring of single DNA

electrophoretic dynamics in real time.

These sorts of studies permit detailed tests

of "reptation" models of electrophoresis

and can begin to address issues in improving separation efficiency in the limit of

high biomolecular strand lengths. Also of

interest are kinetics/dynamics of proteinDNA/RNA binding, which are relevant to

cell regulatory processes and would now

be amenable to detection at the singlemolecule level.

CONTACT: Dr. David J. Nesbitt

(303) 492-8857

djn@jila.colorado.edu

Single-Molecule

Measurement with

Nanometer Resolution

The biochemical cycle of mechano-enzymes

generates a force and a displacement that

can be measured at the single-molecule

level. The third new project aims to determine how motor proteins transduce

chemical energy into physical motion.

This research focuses on developing assays

and precision instrumentation to measure

the properties of single DNA-based molecular motors. The enabling technology is

optical tweezers, a focused laser beam

that can manipulate micrometer-sized

beads in solution, allowing measurements

of position and force in the nanometer

and piconewton ranges.

Measurement of steps and stall forces

provide fundamental information on the

mechanics of motion. For many enzymes,

different proposed mechanisms of motion

predict different step sizes. Steps have

been seen for myosin along actin (5.5 nm)

and for kinesin along microtubules (8 nm).

Enzymatic motion along the DNA is measured by anchoring the enzyme to a surface

and monitoring the position of an optically

trapped bead attached to the DNA's distal

end. To date, unitary steps of DNA-based

molecular motors have been too small

to resolve. Their presumed step sizes are

1 .4 nm or smaller, but such steps may be

attenuated by the compliance of DNA.

Building on our demonstration that 0.3 nm

steps of a stuck bead can be resolved, we

are building a microscope for measuring

1 nm motion along DNA. The electronics

for this microscope are a high bandwidth

(250 kHz) quadrant photodetector connected to a differential normalizing amplifier. These detectors do not exhibit wavelength-dependent reduction in bandwidth

as seen in earlier designs. By incorporating

PZT mirrors instead of acousto-optic deflectors, we eliminate the nanometer-sized,

artifactual steps obsen/ed to arise from

standing waves inside the AO crystal.

CONTACT: Dr. Thomas T. Perkins

(303) 492-8186

tperkins@jila.colorado.edu

Figure 3. Using a modified microscope,

Tom Perkins measures the motion generated

by a single enzyme moving along DNA.

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 of physical reference data, and to

evolve protocols to ensure interoperability in the exchange of scientific and engineering data.

WWW Dissemination

of Information

INTENDED OUTCOME AND

BACKGROUND

The Office of Electronic Commerce in

Scientific and Engineering Data (ECSED)

is responsible for the Physics Laboratory

(PL) world wide web (WWW) pages at

physics.nist.gov. We produce material

for WWW 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 WWW dissemination. We design

and develop effective WWW database

interfaces to facilitate access to the data.

Since June 1994, we have provided a

wide array of information ranging from

physical reference data, technical activities, research and calibration facilities,

technical contacts, publication lists, general

interest, and news items. In a recent month (October 2002), there were nearly one million requests for web pages from

the Gaithersburg server (nearly half from

our =25 online databases), and nearly

8.8 million requests for web pages from

all PL web servers (including time.gov

and tf.nist.gov).

There are many new web databases

currently under development, including:

1) Handbook of Basic Atomic

Spectroscopic Data,

2) Spectral Data for the Chandra

X-ray Observatory,

3) X-ray Transition Energies Database,

4) Chemical Agents Database,

5) Potentials of Alkaline-Earth Dimers,

6) Amorphous Metals Database, and

7) Hydrogen and Deuterium Energies

and Transition Frequencies

(an interactive website).

ACCOMPLISHMENTS

Units Markup Language

We have continued a collaboration with

Lawrence Berkeley National Laboratory

and NIST's Electronics and Electrical

Engineering Laboratory to develop an XML (extensible Markup Language)

schema for encoding scientific measure- ment units. Adoption of this schema will

allow for the unambiguous exchange of

numerical data over the Internet.

We are in the process of creating an

international working group to examine

and discuss the completed first draft of

the UnitsML schema. In addition, we have

begun collaborating with the NIST Information Technology Laboratory to establish

a NIST registry containing SI and non-SI

unit information and to create an XML

registry containing the UnitsML schema.

We anticipate this registry will be used

by our customers to download industryspecific dictionaries of scientific units.

CONTACT: Dr Robert Dragoset

(301) 975-3718

robert, dragoset@nist.gov

52
Molecular Spectroscopy

Tutorials On-Line

We collaborated with the Optical

Technology Division to make available on

the WWW two popular tutorials in nnolecular spectroscopy. The original documents

were converted to HTML, and the equations were formatted as both images and

LaTeX to ensure their wide accessibility.

The first of these documents is the extensively cited NBS Monograph 1 1 5, The

Calculation of Rotational Energy Levels

and Rotational Line Intensities in Diatomic

Molecules, http://physics. nist. gov/

DiatomicCalculations. It played a major

role in standardizing the complex conventions and nomenclature used to describe

the quantum-mechanical behavior of

diatomic molecules.

The document describes the derivation

of the intensities of the spectral lines, and

contains a clear discussion of the rotational Hamiltonian and its symmetry properties, necessary for calculating molecular

energy levels. This pedagogical monograph is of interest to the wide community of scientists dependent on molecular

spectroscopy for their success, including

atmospheric and planetary scientists,

astronomers, plasma physicists, and

analytical chemists. It is the accepted, more rigorous companion to the popular

textbook, Spectra of Diatomic Molecules,

written by the late Nobel Laureate

Gerhard Herzberg.

The second tutorial newly offered online is Methane Symmetry Operations,

http://physics.nist.gov/Methane. It was

initially written in response to the needs

of chemists and physicists for conventions

and guidance in working with the complex

mathematics involved in calculating the

rotational energies and intensities of

tetrahedral molecules, such as methane

and carbon tetrachloride. Scientists interested in atmospheric sensing, combustion

diagnostics, and climate change will benefit

from ready access to this document.

CONTACT: Mrs. Gloria Wiersma

(301) 975-5547

gloria.wiersma@nist.gov

Molecular Databases On-Line

We collaborated with the Optical

Technology Division to make available on

the WWW three linked databases of the

microwave and RF spectra of diatomic,

triatomic, and hydrocarbon molecules.

Originally published as spectral tables

in the Journal of Physical and Chemical

Reference Data, the on-line version

includes additional molecules and allows

advanced browsing and searching of

the data—by molecular species, type,

or frequency

Rotational spectral lines for 121 diatomic

molecules, 55 triatomic molecules, and

91 hydrocarbon molecules are included.

The isotopic molecular species, assigned

^ Viow Go Scuikmafkfl Toob v^^Oon Hatp I ^ hllp^A)hyBicajiittgo'ivMWatiieri

Physical Reference Data

Molecular

SpectralDatabases iCTOwc^ves

Si^tomic Spectral Database

Diatomic Spectral Database

Hydrocarbon Spectral Database

quantum numbers, observed frequency,

estimated measurement uncertainty, and

reference are given for each transition. The spectral lines for many molecules and

normal isotopic species have been refit to

produce a comprehensive and consistent

analysis of all the data obtained from

many sources. The derived molecular

properties, such as rotational and centrifugal distortion constants, hyperfine structure constants, electric dipole moments,

rotational g-factors, and internuclear

distances (for diatomic molecules) are

listed with one-standard-deviation

uncertainties for all species.

The Diatomic, Triatomic, and Hydrocarbon

Spectral Databases can be accessed on

the WWW at http://physics.nist.gov/

MWtables. Further information on

additional molecular spectroscopic databases developed by the Office of ECSED

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

Development of these databases was

supported in part by NiST's Standard

Reference Data (SRD) Group and by NIST's

Systems Integration for Manufacturing

Applications (SIMA) program.

CONTACT: Mrs. Karen Olsen

(301) 975-3286

karen.olsen@nist.gov

Figure 1 . Screen capture of a brow/ser

window for the "Molecular Spectral

Databases" main web page.

53
HONORS AND AWARDS

2001 Nobel Prize in Physics

Eric Cornell (I) receives the 2001 Nobel Prize in Physics from King Carl XVI Gustaf of Sweden (r).

Eric A. Cornell, Quantunn Physics Division/JILA, received the 2001 Nobel Prize in Physics,

jointly with his JILA colleague, Carl E. Wieman, University of Colorado, and Wolfgang

Ketterle, Massachusetts Institute of Technology, for "the achievement of Bose-Einstein

condensation in dilute gases of alkali atonns, and for early fundamental studies of the

properties of the condensates." Announced on October 9, 2001, by the Royal Swedish

Academy of Sciences, it is the second Nobel Prize awarded to NIST Physics Laboratory

scientists. In 1997, William D. Phillips received the Nobel Prize for pioneering research

on cooling and trapping atoms with laser light. The Bose-Einstein condensate, or BEC, is

essentially a new form of matter that allows scientists to study the strange and extremely

small world of quantum physics. Its creation in 1995 by Cornell and Wieman established

a new branch of atomic physics that has provided a treasure-trove of scientific discoveries,

including the atom laser, first demonstrated by Ketterle, quantum whirlpools, atom waveguides, and other coherent atom-optical phenomena.

The Bose-Einstein condensate, first demonstrated

by NIST and University of Colorado scientists

at JILA, was Science magazine's 1995 Molecule

of the Year. A new state of matter, the BEC

"superatom," forms as rubidium atoms trapped

in a magnetic field are cooled to a temperature

close to absolute zero. The graphic shows

three-dimensional, successive snapshots in

time during which the atoms are cooled to

less than 170 billionths of a degree.

54
Max Born

Award

John L. Hall

Quantum Physics

Division, was presented the Optical

Society of America's

Max Born Award

"for pioneenng the

field of stable lasers, including their applications in fundamental physics and, most

recently, in the stabilization of femtosecond lasers to provide dramatic advances in

optical frequency metrology." Jan is one

of the "fathers" of today's laser-generated

optical combs that have allowed us to

directly connect the optical and

microwave frequency regimes.

Presidential

Rank Award

John L Hall also received a 2002

Presidential Rank Award from the U.S.

Office of Personnel Management for

exceptional technical accomplishments

spanning four decades of research in

the Quantum Physics Division at JILA.

Dr. Hall was one of the first scientists to

join JILA when it was established in 1962

as a unique, interdisciplinary partnership between NBS and the University

of Colorado.

William 0. Baker

Award

Deborah S. Jin,

Quantum Physics

Division, was awarded the National

Academy of Science

Award for Initiatives

in Research, "for her

experimental realization and characterization of a new quantum system, the vaporphase degenerate Fermi gas." Known as

"the Baker Prize," the award recognizes

innovative young scientists for research

likely to lead towards new capabilities

for human benefit.

Maria

Goeppert-Mayer Award

Deborah S. Jin was also awarded the

Maria Goeppert-Mayer Award of the

American Physical Society, "for her innovative realization and exploration of a

novel quantum system, the degenerate

Fermi atomic gas, and the scientific

promise portended by her pioneering

work." This award recognizes the wideranging future implications of work in

ultra-cold gases.

Archie Mahan Prize of the Optical Society of America

(r to I) Edward W. Hagley, Charles W. Clark, and Lu Deng, Electron and Optical Physics

Division, William D. Phillips, Atomic Physics Division, and Keith Burnett, Oxford University

were awarded the Archie Mahan Prize of the Optical Society of America, "for authorship

of The Atom Laser, a focused and well-organized article that succinctly connects recent

observations in the field of phase coherent matter waves with early 20*^ century research

on Bose-Einstein condensation."

55
Presidential Early Career

Award for Scientists and

Engineers

Jun Ye, Quantum

Physics Division,

received a 2002

Presidential Early

Career Award for

Scientists and

Engineers (PECASE),

"for pioneering research on laser interactions

with atoms and molecules and their applications to precision control and measurement

of light fields, matter waves, and optical

frequencies." This Presidential 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

by President George W. Bush in a White

House ceremony.

100 Top Young

Innovators

Jun Ye was also chosen as one of the

world's "100 Top Young Innovators"

by Technology Review, published by the

Massachusetts Institute of Technology. The

TR100, all individuals under 35 years of age,

are recognized for their contributions to

technology. Dr. Ye's work is in the fields

of ultrasensitive high-resolution laser spectroscopy, cold atoms, continuous-wave

and ultrafast-pulse laser stabilization,

and optical frequency standards.

Arthur S. Flemming Awards

Leonard M. Hanssen, Optical Technology Division, received a 2002

Arthur S. Flemming Award, "for developing and establishing innovative infrared technology for measuring optical properties of materials." These achievements have established NIST as the world leader

in infrared measurement science and standards and have played

a critical role in the success of U.S. defense and remote-sensing

satellite systems dependent on state-of-the-art infrared technology.

Steven L. Rolston, Atomic Physics Division, received a 2002

Arthur S. Flemming Award, "for innovative leadership in the study

of new physical phenomena in ultra-cold atomic gases, including

the first creation of ultra-cold plasmas and strongly-coupled plasmas."

Dr Rolston's research is part of the Laboratory's program to develop

new laser cooling and trapping techniques and applications.

John H. Burnett, Atomic Physics Division, received a 2002 Arthur

S. Flemming Award, "for developing and applying world-class

measurement systems critically needed for the design of advanced

photolithography manufacturing tools." Dr. Burnett measured a

refractive effect called "intrinsic birefringence," showed that it was

sufficiently large in candidate lens materials to prevent photolithography tools from focusing properly at the targeted wavelength of

1 57 nm, and proposed methods for overcoming the problem.

Service to America Medal

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

the 2002 Service to America Medal, "for career achievement,"

cosponsored by the Atlantic Media Company (Government

Executive Magazine, National Journal, and The Atlantic Monthly)

and the Partnership for Public Service. She was cited for being the

founding director of the award-winning NIST Physics Laboratory,

pioneering the practical application of emerging technologies, enhancing scientific career

opportunities for women and minorities, and fostering a culture of excellence that has

made NIST one of the world's preeminent research institutions.

56
William F. Meggars

Award

American Physical

Society's Outstanding Thesis Award

James C. Bergquist,

Time and Frequency

Division, was recognized with the

William F. Meggars

Award of the Optical

Society of America

(OSA). The award is "for seminal contributions to high-resolution, high-accuracy

laser spectroscopy with applications to

fundamental metrology and clocks."

Dr Bergquist developed the world's most

stable laser and used it as the local oscillator for an optical atomic clock based on

a single mercury ion. This work is central

to the most accurate optical-frequency

measurement ever made, and the first

optical-frequency standard with a

microwave-frequency output.

Brian DeMarco was awarded the 2002 Outstanding Doctoral Thesis

Award by the American Physical Society's Division of Atomic, Molecular,

and Optical Physics (DAMOP). This award recognizes thesis research

of outstanding quality and achievement. Dr DeMarco's thesis,

entitled "Quantum Behavior of an Atomic Fermi Gas," concerned

the extension of the magnetic-trapping and evaporative-cooling techniques used to produce atomic Bose-Einstein condensation to create

the first quantum-degenerate Fermi gas of atoms. His work included measurements of the

atomic-collision mechanisms by which such gases reach thermal equilibrium. This work was

carried out at JILA, in collaboration with Dr Deborah Jin of the Quantum Physics Division.

Dr DeMarco now has a postdoctoral appointment in the Ion Storage Group of the

Laboratory's Time and Frequency Division.

Fellowship of the American Physical Society

Zachary H. Levine, Electron and Optical Physics Division, was elected

a Fellow of the American Physical Society "for leadership in demonstrating x-ray tomography of integrated circuit interconnects with

submicron resolution." Dr Levine has made both theoretical and

expehmental contributions to the field of high-resolution x-ray imaging and was recently awarded a patent, "Parallel X-Ray Tomography"

for the measurement techniques he pioneered.

Carl J. Williams, Atomic Physics Division, was elected an APS Fellow,

"for definitive calculations of atomic collision processes, which have

improved our understanding of photoassociation spectroscopy,

dynamics of Bose-Einstein condensates, and effects of radiation retardation on atomic collisions." Dr. Williams' work relates to the NIST

experimental program in laser cooling and trapping and is foundational for the quantitative understanding of cold-atom collisions.

57
Sigma Xi (NIST Chapter)

Award for Support to

Scientists

Anita K. Sweigert,

Physics Laboratory

Office, received the

NIST Chapter of

Sigma Xi Award, "for

outstanding support

to NIST scientists."

Ms. Sweigert serves as central coordinator

of the NIST Summer Undergraduate

Research Fellowship program (SURF), an

enormously successful, educational outreach program aimed at providing

research opportunities to college and university students. The class of '02 had 102

students, selected from 195 applications.

The students were placed in all seven NIST

Measurement Laboratories.

Sigma Xi

(NIST Chapter)

Young Scientist Award

IPippa--«i«Piip^ Eric L. Shirley,

Optical Technology

Division, was recognized with a 2002

Sigma Xi Young

Scientist Award, "for

sustained excellence

in his contributions to the quantitative

theory of condensed-matter electronic

structure." This award highlights his work

in condensed-matter (solid-state) theory,

which includes studies of x-ray absorption

by crystals. His calculations, based on the

electronic band structure of the crystals

and including electron-(core) hole

interactions, have proven to be the

best in the world.

Women of Color

Research Leadership

Award

Maria E. Nadal,

Optical Technology

Division, received

the 2002 Women

of Color Research

Leadership Award.

The award, given to

elite women in government and defense,

honors Dr. Nadal, "for innovative research

and scientific leadership in optical properties measurements in support of industry

and government." The award is presented

by Career Communications Group, Inc.

(CCG), publisher of U.S. Black Engineer

& Information Technology, and Hispanic

Engineer & Information Technology magazines. Dr. Nadal has developed new standards for reflectance and new measurement services for such hard-to-characterize properties as gloss, luster, and sheen,

which strongly influence the appearance

of materials.

58
Gold Medal (DoC)

The Gold Medal is the highest honor award conferred

upon an employee by the Department of Commerce, for

"distinguished performance characterized by extraordinary

notable, or prestigious contributions that impact the mission

of the Department of Commerce and/or operating unit

and which reflect favorably on the Department.

Bert M. Coursey, Ionizing Radiation Division, received tine

Department of Commerce Gold Medal, "for leadership in helping

solve the problem of anthrax-contaminated mail, detecting nuclear

and radiological threats, and ensuring public safety."

Dr. Coursey is recognized for his leadership in helping to protect

first responders and the American public from terrorist attacks.

An expert in radiation measurement technology, he worked with

the U.S. Postal Service, the Armed Forces Radiobiology Research

institute, and industry to develop a system for decontaminating

more than 20 million letters and 200,000 parcels, and is leading

the development of a national measurement system for combating

nuclear smuggling and radiological threats. He is shown here to

the right of his colleagues from the U.S. Postal Service and the

Armed Forces Radiobiology Research Institute, hurrying to an

irradiation facility in Lima, Ohio, to validate the process using

an instrumented box of mail.

Katharine B. Gebbie and William R. Ott received the Gold

Medal, "for leading NIST's Physics Laboratory (PL) and creating

an atmosphere in which innovative scientific research flourishes

in support of NIST's mission." Drs. Gebbie and Ott have led the

Physics Laboratory since its inception 13 years ago.

Their strong and enduring support of research directed at important measurement challenges, such as developing the world's most

accurate clock, providing measurement support for protecting the

U.S. mail from bioterrorism, probing the limits of quantum-based

measurements, and improving medical treatments and diagnosis

with optical and ionizing radiation technologies, has resulted in

numerous awards and recognition for the Laboratory's scientists

and programs, including the Nobel Prize in 1997 and 2001.

59
Silver Medal (DoC) Bronze Medal (NIST)

The Silver Medal is the second highest honor awarded by the

Department of Commerce, for "exceptional performance characterized by noteworthy or superlative contributions that have a

direct and lasting impact.

(I to r) Eric L. Shirley, Optical Technology Division, John H.

Burnett, Atomic Physics Division, and Zachary H. Levine,

Electron and Optical Physics Division, received the Silver Medal,

"for advancing next-generation senniconductor lithography by the

discovery of deep ultraviolet birefringence in calcium fluoride."

Through a combination of theoretical work and laboratory measurements, the team developed a precise understanding of the

effect, and devised conceptual methods for engineering around

it. By providing an early warning to the semiconductor industry

about a critical, previously neglected problem, the three scientists

smoothed the way for the timely introduction of the next

generation of microlithography

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 of unusual initiative or creative ability in the

development and improvement of methods and procedures. It is

also given for significant contributions affecting major programs,

scientific accomplishment within the Institute, and superior

performance of assigned tasks for at least five consecutive years.

Karen J. Combs, Physics Laboratory Office,

received the Bronze Medal, "for improving

NIST-wide administrative and technical

support." Mrs. Combs led a NIST-wide

administrative working group that promoted

efficiencies in administrative policies and

procedures, improved NIST-wide communication among and between administrative disciplines, encouraged

collaboration and cooperation, and improved training and

career development.

Brian E. Zimmerman, Ionizing Radiation Division, received the

Bronze Medal, "for his leadership of the NIST program for radiopharmaceutical standards." Dr. Zimmerman and his colleagues

provide the national standards for radionuclides used in diagnostic

and therapeutic nuclear medicine. To develop, maintain, and disseminate the national standards for radiopharmaceuticals.

Dr. Zimmerman carries out a vigorous research program focused

on radionuclides used for therapy and

administers a collaborative program with

industry to deliver radiopharmaceutical standard reference materials. He is also collaborating with NIH and developing radioactivity

standards for cancer imaging and therapy

applications.

60
Allen V. Astin

Measurement Science

Award (NIST) Edward Uhler Condon Award (NIST)

The Astin Award recognizes outstanding

acfiievement in the advancement of

measurement science or in the delivery

of measurement services.

Bert M. Coursey,

Ionizing Radiation

Division, received the

Astin Measurement

Science Award, "for

his leadership in developing and providing modern radiation

standards and measurement services for

health care providers." Dr. Coursey's

leadership in measurement science has

improved health care for millions of

Americans. He developed the NIST

Medical-Industrial Radiation Facility (MIRF)

to provide standards for high-energy

radiation therapy. He improved dose standards used in all 1 1,000 mammography

facilities in the Nation (26 million mammograms/year). He led the development

of radiation standards for brachytherapy

used to prevent the closing of artenes

following angioplasty and to treat

prostate cancer (40,000 treatments/year).

He initiated new measurement services for

nuclear medicine applications for imaging

of tumors, infection, cardiac, or brain

function (36,000 procedures/day), and for

radioimmunotherapy and bone palliation

(200,000 therapeutic procedures/year).

The Condon Award recognizes distinguished achievement in written exposition

in science or technology.

(r to I) Edward W. Hagley, Charles W. Clark, and Lu Deng, Electron and Optical

Physics Division, William D. Phillips, Atomic Physics Division, and Keith Burnett, Oxford

University, were awarded the Condon Award, "for authorship of The Atom Laser, Optics

and Photonics News (May 2001), a broadly-accessible account of coherent

matter-wave physics."

Edward Bennett Rosa Award (NIST)

The Rosa Award recognizes outstanding achievements in the development of meaningful

and significant standards of practice in the measurement field.

B. Carol Johnson, Optical Technology Division, received the Rosa

Award, "for research and leadership in developing measurement standards for ensuring the accuracy of remote-sensing instruments monitoring climate change." Dr. Johnson has developed novel optical radiation measurement instruments, standards, and methods for ensuring

the accuracy and reliability of satellite and ground-based instruments

monitoring climate change. Her world-leading research program further supports the

remote sensing community by offenng training and education through formal courses,

lectures, and publications, and by providing instrument measurement validation through

laboratory comparisons. Her efforts have accelerated the advancement of the fundamental

metrology of optical radiation measurements, leading to the development of unique NIST

facilities for calibrating remote-sensing instruments.

61
Equal Employment

Opportunity/Diversity

Award (NIST)

The Equal Employment Opportunity/

Diversity Award recognizes significant

EEO/Diversity contributions that have been

performed in an outstanding manner

Robert A. Dragoset, Office of Electronic

Commerce in Scientific and Engineering

Data, and Chiara F. Ferraris, Building

and Fire Research Laboratory, received

the EEO/Diversity Award, "for organizing

Science: Get Psyched, an annual program

of hands-on demonstrations for hundreds

of girl scouts aimed at increasing interest

in science." In small groups, the girls visit

successive rooms and interact with NIST

scientists providing lively science demonstrations and supervising the girls' participation. The scouts also attend panel

discussions where they can ask female

scientists what it is like to be a scientist.

The volunteer program, now in its ninth

year, aims to increase the pipeline of

young scientists.

Safety Award (NIST)

The Safety Award for Superior Accomplishment recognizes unusually significant

contributions to the NIST Occupational Safety and Health program activities.

(I to r) Timothy R Mengers, Occupational Health and Safety Division, Michael P.

Unterweger and Bert M. Coursey, Ionizing Radiation Division, Zachary H. Levine,

Electron and Optical Physics Division, Stephen M. Seltzer, Ionizing Radiation Division,

Thomas G. Hobbs, Occupational Health and Safety Division, and Charles W. Clark,

Electron and Optical Physics Division, were awarded the NIST Safety Award, "for prompt

action to enhance the security of NIST radiation sources and radioactive materials in the

aftermath of the terror attacks of September 1 1

, 2001 ." This group demonstrated exceptional initiative in organizing a team to identify ways to improve security of NIST facilities

where radiation sources are used and stored. A phased plan of action was developed;

some steps were taken immediately, and others were presented to NIST Administration

for rapid implementation as part of NIST-wide security efforts.

62
PHYSICS LABORATORY RESOURCES

Key to Table

Abbreviations:

SIRS - Congressionally appropriated

funds for NIST's Scientific and Technical

Research and Services

ATP - Intramural research funds provided

to support the goals of the NIST

Advanced Technology Program

OA - Funds provided by other agencies

in support of research that they request

Other - Other sources of funding,

including calibration fees

Federal Agencies

Supporting Physics

Laboratory Research

Department of Defense

National Aeronautics and Space

Administration

Department of Energy

Department of Commerce

Department of Health and

Human Services

National Science Foundation

Environmental Protection Agency

Department of Justice

PHYSICS LABORATORY RESOURCES 1998 - 2002

($ MILLIONS)

1999 2000

STRS 33.1 34.7 34.8 37.1 39.9

ATP 1.8 1.8 1.8 2.1 2.9

OA 9.5 10.2 10.6 11.9 13.6

Other 3.8 3.7 4.4 4.5 5.0

TOTAL

I

48.2 50.4 51.6 55.6 61.4

J

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'fclairage

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

Charles Clark, Chief

Atomic Physics Division

Wolfgang Wiese, Chief

V J

r

Optical Technology Division

Albert Parr, Chief

J

^\

f Ionizing Radiation Division

Bert Coursey, Chief

)

r Time and Frequency Division

Donald Sullivan, Chief

J

f Quantum Physics Division

Jannes Faller, Chief

64
EDITORS:

Jonathan E. Hardis, William R. Ott,

and Gloria G. Wiersma

Physics Laboratory, National Institute of Standards and Technology

U.S. Department of Commerce

Donald L. Evans, Secretary

Technology Administration

Phillip J. Bond, Under Secretary for Technology

National Institute of Standards and Technology

Arden L. Bement, Jr., Director

NIST SP 994

February 2003

Disclaimer: any mention of commercial products is for

information only; it does not imply NIST recommendation or endorsement, nor does it imply that the products mentioned

are necessarily the best available for the purpose.
NIST PHYSICS LABORATORY

100 Bureau Drive, Stop 8400

Gaithersburg, MD 20899-8400

www@physics.ni5t.gov