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 Quantum Physics Division: to provide - Spectral Irradiance and Radiance fundamental understandings of nano-, Responsivity Calibrations Using Preeminent performance in measurement Uniform Sources (SIRCUS) Facility bio-, and quantum optical systems in part- science, technology, and services. nership with the University of Colorado - Synchrotron Ultraviolet Radiation Facility (SURF HI) at JILA. PL MISSION - W.M. Keck Optical Measurement Office of Electronics Commerce in Laboratory The mission of the NIST Physics Laboratory Scientific and Engineering Data: to is to support U.S. industry, government, coordinate and facilitate the electronic dis- Standard time dissemination services: and the scientific community by providing semination of information via the Internet. measurement services and research for - Radio stations WWV, VWWH, electronic, optical, and radiation technology and WWVB PL RESOURCES The Laboratory provides the foundation -Automated Computer Time for metrology of optical and ionizing 199 full-time staff (147 scientific) Service (ACTS) radiation, time and frequency, and with expertise in: - Internet Time Service (ITS) fundamental quantum processes. - Atomic, molecular, and optical physics Measurement and calibration - Computational physics services for: - Condensed matter physics PL GOALS - Color and color temperature - Health physics Physics Laboratory develops goals within - Dosimetry of x rays, gamma rays, - physics electrons its mission and focus areas. These include Medical and health care quality assurance, nanoscale - Nuclear physics - High-precision time

measurements and data, and measure- - Biophysics - Neutron sources and neutron dosimetry ments and standards that support home- - Chemistry - Optical wavelength land security. In addition to these over- - Metrology and precision measurement - Oscillator frequency arching focus areas, which are shared by - Phase and amplitude noise other NIST Laboratories, PL has substantial $61 million annual budget - programmatic interest in time and Photodiode spectral responsivity frequency, optical and photonic, and - Photometry (e.g., luminous intensity, Unique facilities, including: environmental and energy metrology luminous flux, illuminance) and applications. -Controlled Background - Radiance temperature Radiometric Facility - Radioactivity sources Electron and Optical Physics Division: - Electron Beam Ion Trap (EBIT) - Spectral radiance and irradiance to support emerging electronic, optical, - Electron Paramagnetic - and nanoscale technologies. Spectral transmittance and reflectance Resonance Facility

Division: to determine - EUV Optics Fabrication and Atomic Physics PL WEB SITE Characterization Facility atomic properties and explore their - applications. High-Resolution UV and Optical http://physics.nist. gov/ Spectroscopy Facility

Optical Technology Division: to provide - Low-Background Infrared the foundation of optical radiation measure- Radiation Facility

ments for our Nation. - Magnetic Microstructure Measurement Facility Ionizing Radiation Division: to provide - Medical-Industrial Radiation Facility (MIRF) the foundation of ionizing radiation - Nanoscale Physics Laboratory measurements for our Nation - Neutron Interferometer and Optics Time and Frequency Division: to Facility (NIOF) provide the foundation of frequency - NIST Beowulf System

civil timekeeping for measurements and - Radiopharmaceutical Standardization our Nation. Laboratory

1 DIRECTOR'S MESSAGE

We hope 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 funda- While our Internet Time Service provides We provide the basis for such SI dehved mental triad of standards, measurements, official U.S. time in a billion daily transac- units as the hertz (frequency), the and data in a climate of vigorous and tions, we are also pursuing research on becquerel (radioactivity), and the optical competitive research. We believe that the trapped ions for the next generation of watt and the lumen (light output). At quality of our service stems in large meas- frequency standards—and quantum-logic the same time, scientists in the Physics ure from the breadth, vigor, and excellence devices. Similarly our Ionizing Radiation Laboratory work with industry to develop of our research programs and that our Division is developing highly sensitive new measurement technologies that can contributions gain credibility because neutron detectors for homeland security be applied to such fields as communica- they are based on the best technical while also using ultracold neutrons to tions, microelectronics, nanomagnetics, judgment available. investigate symmetries and parameters photonics, industrial radiation processing,

of the nuclear weak interaction. the environment, health care, transporta- For example, our Time and Frequency tion, space, energy security, and defense. Division is delivering seven different kinds We maintain the U.S. national standards of time and frequency services while also for the Systeme International (SI) base developing optical-frequency atomic units of time (the second), light (the clocks, chip-scale atomic clocks, and a candela), and non-contact thermometry futuristic atomic clock for space flight. (the kelvin, especially above 1200 K).

2 Our partners are many and our outreach We have been recognized for the quality The Physics Laboratory is at the forefront of is extensive. For optical radiation measure- and excellence of our programs and the nascent field of quantum information nnents, we rely heavily on the Council for staff many times over the years, by the processing—computing and communica-

Optical Radiation Measurements (CORM), American Physical Society, the Optical tions—challenging preconceived notions formed to help define pressing problems Society of America, and other leading of computational complexity and commu- and projected national needs in radiometry scientific organizations. Members of nications security. Similarly, the Physics and photometry. Its aim is to establish a our staff have been elected to fellowship Laboratory has been a leading center for consensus on industrial and academic in the National Academy of Science, metrology at the nanoscale, since before requirements for physical standards, the American Association for the "nanotechnology" gained prominence. calibration services, and interlaboratory Advancement of Science, the American We pioneered electron-spin microscopy, collaborative programs in the fields of Association of Physicists in Medicine, and which images magnetic materials, and our ultraviolet, visible, and infrared measure- other esteemed bodies. And twice since unique EUV optics facility supports the ments. Similarly, the Council on Ionization 1997, Laboratory staff members have electronic industry in its drive to develop

Radiation Measurements and Standards won the Nobel Prize in Physics. Beginning advanced lithographic systems for

(CIRMS) helps to advance and disseminate on page 54 of this report, we highlight producing ever smaller chips. the physical standards needed for the some of the awards and honors bestowed As you browse this summary of the safe and effective application of ionization upon us in 2002. Physics Laboratory, we expect you will radiation, including vacuum ultraviolet, Our talent is focused on meeting today's want to learn more. We invite you to visit X ray, gamma ray and energetic particle challenges— in health care, quantum our web site, http://physics.nist.gov/, such as electron, proton, and neutron. technologies, and nanoscale metrology, and we invite your inquiries and interest in When we can assist in an important to name but a few. For health care, the measurement services and collaborations. area of measurement or research, we Physics Laboratory conducts research may form Cooperative Research and on standards to enable hospitals to use Development Agreements with industry nuclear medicine more effectively We groups or individual firms. Laboratory staff develop ways to image single biomole- serve with distinction in standards-develop- Katharine Gebbie cules and to use terahertz-frequency ment committees, and readily give of their Director, Physics Laboratory signals as diagnostic tools. time to assist the public.

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 near-term measurement issues faced by the magnetic data-storage industry. for fabricating nanostructures and measuring their

Our STM program is focused on under- electronic and magnetic properties. standing the mechanisms of growth of

nanostructures on surfaces and determin- Nanoscale Electronics SEMPA enables us to use conventional ing their electronic properties. In recent scanning electron microscopy (SEM) to years the STM program has been particu- and Magnetics image nanometer-scale magnetic struc- larly concerned with the magnetic multi-

layer materials that have been investigated INTENDED OUTCOME AND ture, through spin-polarization analysis of by SEMPA. The complementarity of SEMPA BACKGROUND secondary electrons ejected from the sam- has elucidated ple. It has several unique capabilities that and STM measurements

The intended outcome of this work is distinguish it from other magnetic imag- many connections between conditions the continuous improvement of tech- of layer ing techniques: it is a surface-sensitive growth and magnetic-device niques for fabncating and characterizing technique, and so is especially well suited performance. nanometer-scale electronic and magnetic for in situ studies of thin-film and surface structures, as required to meet current The main current direction of the STM magnetization; it provides a direct meas- and future needs of the semiconductor program is the course of research made urement of the magnetization of a materi- and data-storage industries. possible by the recently-completed al region, rather than of a magnetic field; Nanoscale Physics Laboratory. The labora-

Our main tools for pursuing this program it has the high spatial resolution (about tory was designed with the goal of meas- are scanning electron microscopy with 10 nm), long working distance, and large uring quantum-electronic structures with polarization analysis (SEMPA) and scan- depth-of-field characteristic of SEM; and it atomic-scale imaging resolution and high ning tunneling microscopy (STM). The facilitates simultaneous measurements of electron-energy resolution. Samples can Electron Physics Group in the Division has the magnetization and the topography. be grown in situ and probed with mag- been a leading innovator in both of these SEMPA studies have led to a number of netic fields of up to 10 T at temperatures techniques, which are outgrowths of breakthroughs in understanding the basic down to 2.5 K. work begun at NIST in the 1970s. mechanisms of magnetism on the micro-

scopic scale, and have also addressed

4 ACCOMPLISHMENTS = h/2e Real-space measurements of vortex lat- tices are difficult because the length scale

Nanometer-Scale of the vortex unit cell is in the nanometer

Measurements of the range for field strengths on the order of

Vortex Lattice in a Type-ll 1 T. Such measurements are now possible Superconductor using cryogenic scanning tunneling microscopy, which probes the electronic We have made the first real-space meas- structure of the superconductor on the urements of the hexagonal-to-square atomic scale. symmetry transition in the vortex lattice of

VgSi, a type-ll superconductor. The mixed Measurements of the symmetry transition state in a type-ll superconductor is charac- in VjSi were made by recording spatial terized by the properties of the vortex or Figure 1 . Vortex flux lattice in VjSi observed in maps of the local density of states (LDOS) STM Fermi-level conductance image at 1-1=3 T flux lattice that forms in the presence of of the superconductor as a function of and T=2.3 K. The peaks indicate the location an applied magnetic field. Vortices are magnetic field, using the low-temperature of vortices with a single flux quantum of formed at points where the magnetic field scanning tunneling microscope of the magnetic flux. penetrates the superconductor in a flux Nanoscale Physics Laboratory in the tube through the sample. The flux pene- Electron Physics Group. At the location of trates the superconductor in quantized the vortex, the superconductor is a normal high values of applied field. For example, units of the flux quantum (o= h/2e), metal and has a much higher density of the optimization of vortex pinning in with the region near the core of the states for energies inside the supercon- high-Tc materials controls flux creep and vortex acting as a normal metal. As the ducting gap. Thus, spatial maps of the is responsible for the high critical currents density of vortices in the material increases, LDOS show a bright spot at the location needed for the operation of supercon-

vortex lattice is formed by the interactions of the vortex. a ducting magnets. Probing the underlying between the flux tubes or vortices. physics of the vortex lattice is not only of

technological importance, it is also the Many of the important applications of key to understanding more complex superconductors rely on the formation interactions, such as the coexistence and stabilization of the vortex lattice at of superconductivity and magnetism.

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 1 [jnn symmetries in the electronic structure of o the superconductor play an important Magnetization role, as they directly link the symmetry Direction of the vortex lattice to the underlying crystal structure.

Figure 3. SEMPA image of a magnetic Co ring (center) along with a micromagnetic simulation (right). CONTACT: Dr. Joseph A. Stroscio (301) 975-3716 By comparing different sized thin-film netizations of the layers between parallel [email protected] elements grown under various conditions, and antiparallel. In other configurations,

the SEMPA images revealed that the it appears that the magnetization of one

Magnetic Nanostructures interplay between shape and crystalline layer rapidly precesses around that of the in Patterned anisotropy can lead to unexpected mag- other layer. Ferromagnetic Rings netic configurations. In particular, undesir- These effects, which were observed start- able magnetic vortices can be induced in Small, patterned, magnetic, thin-film ing in 1999, are being studied for two thick-walled rings during switching. The structures are a critical part of emerging device applications. If the size of the cur- SEMPA images were also used as a quan- magneto-electronic technologies, which rent necessary to reverse magnetic bits titative test of micromagnetic models range from non-volatile magnetic random- can be reduced sufficiently, spin-transfer that, in turn, can explore regions of the access memories to magnetic biosensor torques could provide a way to switch switching behavior not accessible to arrays. To be useful in devices, the mag- bits in magnetic random-access memory static SEMPA measurements. netic structure of these rings must assume (MRAM). Alternatively, if the interpreta- only a few well-defined magnetic states, tion of recent experiments as precession CONTACT: Dr. John Unguris and the switching between states must (301) 975-3712 is correct, it should be possible to make be reproducible. [email protected] controllable-frequency oscillators.

In collaboration with the Naval Research Lab and the University of Cambridge Switching Nanomagnets Cu Co Cu Co Cu Thin-Film Magnetism Group, we have used A current passing through two ferromag- the NIST Scanning Electron Microscopy nets separated by a non-magnetic spacer with Polarization Analysis (SEMPA) facility layer exerts a torque on each magnetiza- to non-intrusively image the magnetic tion whenever the two magnetization nanostructure of a promising subclass of directions are not parallel. In the appropri- these structures: microscopic magnetic ate configuration, a large enough current Figure 4. Electron spin scattering from rings. The SEMPA images provided a passing through such a multilayer can a ferromagnetic interface. The change first direct look at these magnetic states. switch the relative alignment of the mag- in spin due to scattering rotates the magnetization.

6 We have developed quantitative models of the patterns may be accurately traced for spin-transfer torques to help enable to an atomic frequency, so that the the developnnent of devices based on this patterns can be used as absolute length effect. These models require three types standards on the nano- and micro-scale. of calculations. We have carried out quan- tum-mechanical calculations to determine CONTACT: Dr. Jabez J. McClelland (301)975-3721 the fate of an electron that scatters from [email protected] an interface with a ferromagnet. These calculations show that the transverse component of the incident spin current Electron Beam Induced is absorbed close to the interface. Magnetic Switching

We use this result as a boundary condition Understanding and controlling the mag-

Figure 5. Beating of nanolines: the superposi- in the second type of calculation, semi- netic properties of ferromagnetic thin tion of two nanoscale patterns with slightly classical transport. These calculations films grown on semiconductor substrates different periodicities results in an optically determine the polarization, both magni- is a chtical element in developing hybrid visible beating on the microscale. tude and direction, of the current magnetic/semiconductor magneto- throughout the structure. With the input electronic devices. We use the exquisite from the first-principles calculations, our We have collaborated with scientists from surface sensitivity provided by SEMPA semiclassical calculations reproduce both the University of Nijmegen to make an to systematically explore the properties the transport properties of the structures artifact that facilitates this connection. It of various ferromagnet/semiconductor and the current-induced torques. relies on a technology first demonstrated combinations. As part of this work, we

in the Electron Physics Group in 1993, discovered that electron beams can be Analyzing the calculations in detail high- called laser-focused atomic deposition. In used to induce changes in the magnetiza- lights the important physical processes, its original form, an optical standing wave tion direction in ferromagnetic thin films. which are difficult to access experimentally. focused chromium atoms onto a surface, The calculated torques can be used as creating an array of lines with a highly input to the third type of calculation, precise spacing of 212.78 nm. In the new classical simulations of the magnetization process, two arrays of lines with slightly dynamics. different spacing are superimposed,

creating a beating, or Moire, pattern with CONTACT: Dr. Mark D. Stiles periodicity of 44.46 pm. When viewed (301) 975-3745 [email protected] through crossed polarizers, this pattern is

clearly visible with an optical microscope.

Linking the Micro and Nano The result of this process is that nanome- Worlds with Nanolines ter-scale and micrometer-scale patterns are created on a single substrate in coher- As technologies ranging from electronics ent registration with each other Ongoing and data storage to biotechnology investigations indicate that because of Figure 6. A series of SEMPA images from become more and more miniaturized, the resonant nature of the laser-focused Fe/GaAsd 10) showing the electron-beam- there is an increasing need for ways atomic-deposition process, the dimensions induced magnetization reonentation. to make measurements that bridge the domains of the micrometer and the nanometer

7 When Fe films are grown epitaxially on second strategic focus is the development of the (110) crystal surface of GaAs, the The metrology for extreme-ultraviolet (EUV) optics, the magnetization can be trapped in a

metastable state, oriented along the maintenance of national primary standards for radiometry

[-1 10] direction. Irradiating the sample in the EUV and adjoining spectral regions, and the with an electron beam causes the

magnetization to locally rotate by 90° operation of national user facilities for EUV science

into the stable direction. [100] and applications.

In addition to providing information

is an important tool for determining the regarding domain-wall dynamics in Extreme Ultraviolet Fe/GaAs, this phenomenon may also electronic structure of materials, diagnos- Radiation Metrology provide a means of locally writing mag- ing plasmas, measuring dynamics of the upper atmosphere, and probing the netic information or patterns in Fe films INTENDED OUTCOME AND structure and dynamics of astrophysical with electron-beam precision. Work is BACKGROUND underway to understand the electron- objects. One of the key candidates for The intended outcomes of this program beam/sample interaction that drives next-generation semiconductor lithogra- are: maintenance and continuous is light source, since its short the reorientation, and to investigate its phy an EUV improvement of the national primary potential for electron-beam writing of wavelength (13 nm vs. 193 nm for pres- measurement standards for extreme- magnetic information. ent ultraviolet production lithography) ultraviolet radiation (EUV: wavelengths enables diffraction-limited imaging of between 2 nm and 200 nm, from soft CONTACT: Dr. John Unguris features with smaller critical dimensions. X rays to vacuum ultraviolet), development (301) 975-3712 We are working actively with the semi- [email protected] of techniques for fabricating and charac- conductor industry to develop "optical terizing EUV optical systems, and the bench" capabilities for characterizing development of a synchrotron-based, EUV imaging systems. national primary standard for source-

based optical radiometry. The Division's key tool for EUV optical

metrology is the NIST Synchrotron Division has longstanding responsibility Figure 7. NIST Synchrotron Ultraviolet The Ultraviolet Radiation Facility (SURF III). SURF

Radiation Facility (SURF III) and Beamlines for the primary national radiometric stan- III, the successor to the world's first dedi- 1-5, with principal users and staff. dards in the EUV region. EUV radiation cated source of synchrotron radiation, is a

low energy (< 400 MeV), high beam cur-

rent (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 operat-

ed 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 One of SURF'S main customers is NASA,

which calibrates virtually all its spaceborne

Metrology for Extreme- EUV spectrometers at the spectrometer

Ultraviolet Lithography calibration facility on SURF Beamline 2.

Recent calibrations include instruments New semiconductor industry requirements flown on the Thermosphere Ionosphere for highly accurate EUV reflectivity meas- Mesosphere Energetics and Dynamics urements have provided the impetus for (TIMED) mission, the EOS SORCE SOLSTICE an international comparison of results A and B missions (Earth Obsenying System, of measurements at four different EUV

Figure 9. White light from SURF III (right) is Solar Radiation Climate Experiment, Solar facilities: the Advanced Light Source at reflected by diffraction grating (foreground), Stellar Irradiance Comparison Experiment), Lawrence Berkeley National Laboratory to display spectrum on screen. and the SETI/UCSB (VUV Stimulated (CXRO), the PTB instrument at the BESSY Mid-IR Expenment) mission. storage ring in Berlin, the ASET instrument

in Japan, and SURF III at NISI Figure 8 shows the results for one sample We have completed an upgrade of the

that is typical of the set. From these accelerator to improve the radiometric Each lab provided at least one multilayer results we are confident that the NIST- performance, both in accuracy and spec- mirror, which they measured before and

quoted uncertainty of 0.3 % is a reliable tral range. Absolute flux uncertainties are after the entire set had been measured at

estimate. This uncertainty represents a better than 1 % from 2 nm to beyond the other facilities. (This was to account factor-of-ten improvement over earlier 400 nm. The storage ring now operates for the aging of the mirrors.) For each instrument performance, before a com- typically at an electron energy of 380 mirror, the object was to determine the prehensive set of improvements were MeV, rather than the 284 MeV energy wavelength of peak reflectivity, and the

made in response to more stringent of SURF II. This results in a significant reflectivity at that wavelength. industry demands. increase in the flux at soft x-ray wave-

lengths. Testing of the magnet system

CONTACT: Dr. Charles S. Tarrio has shown the capability of operating 0 (301) 975-3737 0.625 from 73 MeV to 417 MeV

PT i 0.624 [email protected]

0.623

0.622 NI5T

0.621 j Absolute Radiometry

0.620 III ASET at SURF

13,480 13.485 13.490 13.495 13.500 13,505 13.510 The NIST Synchrotron Ultraviolet Radiation Wavelength of Peak Reflectivity [nm] Facility (SURF III) serves as the Nation's

Figure 8. Results of the international compari- primary standard for absolute source- son of reflectivity and wavelength of maximum based optical radiometry from the visible reflectivity of a test EUV multilayer mirror, from through the extreme-ultraviolet (EUV)

Center for X-Ray Optics, (Berkeley CA), the spectral regions. It supports a variety of the Physikalisch-Technische Bundesanstalt scientific and measurement missions, Figure 10. The new white-light radiometry (Berlin), the Association of Super-Advanced primarily in the EUV. endstation on Beamline 3. Electronics Technologies (Japan), and NISI

9 SURF III Status Display third strategic focus is metrology for coherent Beam Current The 74.15 nlA Electron Energy matter-wave and quantum information processing 380.0 MeV

Lifetime RK Voltage 12.76 h 27,33 kV devices.

Orbital radii s 337.0773 mm Ring Vacuum 5.43E-10hPa FWHM X FWHM Y project to develop a testbed for quantum- '2:00 14:00 16:00 17:53 Coherent Matter-Wave 4.67 mm 1.00 mn, , ^'"'^ PeaklA/avelength communication systems, together with Last updated: 09-Aug-2002 17:53:33 6.40 nm . .- .Ui ^mjg^jm and Quantum Comment: Normal operation the Atomic Physics Division and the

Information Technology Laboratory. Figure 1 1. SURF operations at high current Information Processing for EUV optics characterization. Metrology

INTENDED OUTCOME AND ACCOMPLISHMENTS BACKGROUND Coherent Matter-Wave The intended outcome of this program Device Physics is to provide measurements and data

needed for the development of ultracold The development of coherent matter- sources, atom technology, in particular the use of wave based on Bose-Einstein condensates of dilute atomic coherent matter waves in sensors, atom gases, has

interferometers, and quantum information opened up a new frontier of precision

processing devices. measurement. There are long-range prospects for the use of such sources for Figure 12. SURF at low current for EUV The Division maintains two efforts in this sensitive gravitational and inertial sensors, spectrometer calibration. area, one theoretical and one expehmen- direct-write atomic lithography, and

tal. The theoretical program is focused quantum information processing. In on quantitative modeling of degenerate collaboration with experimental programs SURF can be run under a wide variety quantum gases, with particular attention in Gaithersburg and Boulder, we work on of operating conditions according to the to the dynamics of Bose-Einstein conden- quantitative studies of the dynamics of needs of different users. Figures 1 1 and sates subject to external forces, e.g., coherent matter-wave systems, with a 12 show the quite different conditions manipulation of condensates confined in particular focus on first-principles model- required for EUV optics metrology and an optical lattice. This program is an out- ing and simulation of their dynamics. satellite spectronneter calibration. growth of extensive collaborations with

subject of current interest is experimental groups at NIST, JILA, and One the CONTACT: Dr Mitchell L. Furst dynamics of ultracold atoms in optical (301)975-6378 elsewhere, begun in the mid-1990s. lattices, a candidate system for quantum [email protected] The primary goal of the experimental pro- information processing. Optical lattices are

is the development of deterministic gram defect-free crystal potentials. Solid-state

atom-delivery systems, i.e. devices that crystal structures tend to favor certain can deliver one and only one atom to a types of lattices and their actual potentials

predetermined location, on demand. In are very complex. Optical lattices, in con-

addition, the Division is a partner in a trast, are completely controllable, with the

potentials being perfectly sinusoidal; or,

in general, a sum of sinusoidal potentials.

10 i5r 15 10^ Figure 13. Two-dimensional optical lattice

potential (left), and its associated lowest 10 ^1. 10 10" Wannier state (right). Potential and

density distributions are shown. >^ 0 10"

-5

10 -10 -5 0 5 10 15 Potential -10 -5 0 5 10 15 Density X [E J x[X]

We have calculated the band structure With these questions in mind, we have The result is a source in which single for 2D and 3D optical lattices for parame- recently developed a way to reliably iso- atoms can be extracted and replenished ter regimes appropriate to the experi- late one-and only one-atom, essentially reliably at rates ranging from several tens ments at NIST. The energy eigenstates "on demand." Using laser cooling and of atoms per second in the current config- determined by these calculations, known trapping techniques, we have isolated uration to several hundred per second or as Bloch states, are useful for calibrating single, cold chromium atoms in a magne- more in the theoretical limit. Applications lattice properties (e.g., beam orientation to-optical trap, and used feedback control for these deterministically produced atoms and depth). over the loading and loss processes to range from fundamental studies of quan-

eliminate nearly all the random fluctua- tum coherence, which take advantage of As a case study, we investigated the types tions in trap occupation number that the purely quantum nature of isolated of lattices that can be prepared for a 2D would ordinarily plague such a trap. atoms, to structured doping of nanostruc- system made by three light fields in the tures, in which a small, countable number plane. We showed that, for this simple of dopant atoms is required in nanostruc- arrangement, all five types of 2D lattices tures to tailor their electronic, magnetic, can be made (square, rectangular, cen- or optical properties. tered rectangular, oblique, and hexagonal).

CONTACT: Dr. Jabez J. McClelland CONTACT: Dr. Charles W. Clark (301) 975-3721 975-3709 (301) [email protected] [email protected]

Atoms on Dennand

Nanotechnology deals with understanding and manipulating matter on the nanome- ter scale—that is, on the scale of a few tens of atoms to a few hundred atoms. As

Figure 14. Atoms on demand; the chance we gain skill and knowledge in this of having exactly one atom goes from the regime, the natural question arises, can random-walk value of 37 % to a value near we go further? Can tools be developed 100 % by the application of feedback. that work controllably with single atoms individually, and, if so, what new science and applications will become available?

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 and optical characterization and manipu- lation of single molecules, biomolecules, of electromagnetic-matter interactions and to explore and biomembranes. new applications for laser cooled and trapped atoms.

Light-Matter The development of laser cooling and ACCOMPLISHMENTS trapping techniques allows exquisite From an Atomic BEC to Mott- Interactions and control over the motion of atoms. Such Insulator to a Molecular BEC Atom Optics control has been exploited to build more precise atomic clocks and gravity gra- Recent theoretical calculations show how INTENDED OUTCOME AND diometers. These techniques also enable to obtain a quantum phase transition BACKGROUND the study and manipulation of atoms and that takes the superfluid state appropriate

This strategic element focuses on the molecules under conditions in which their to a BEC in a shallow, three-dimensional, or behavior dominates. physics of laser cooling and electromag- quantum wave optical lattice and transforms it to a Mott- netic trapping of neutral particles, the This research has revolutionized the field insulator state appropriate to a deep opti- manipulation of Bose-Einstein conden- of matter-wave optics. cal lattice. In the superfluid state all the sates (BECs), and the use of optical dipole atoms are identical, whereas in the deep Our research includes theoretical and forces as a new tool for analyzing of lattice, Mott-insulator state the atoms are expehmental projects that contribute to microscopic objects in biochemistry. It distinct since they are individually labeled the understanding and exploitation of includes both fundamental and applied by their lattice position. Bose-Einstein condensation of neutral studies, such as developing measure- atoms, matter-wave optics, optical and We have shown that if we start with an ment techniques for biomolecular systems magnetic control of trapped-atom colli- average of two atoms per optical lattice and developing a quantum information sions, advanced laser cooling and collision site and increase the lattice depth to processor A strong theoretical-experimental studies for atomic clocks, ultracold plas- obtain a Mott-insulator state with exactly collaboration is aimed at interpreting mas and Rydberg atoms, the study of two atoms per well site, we can then experimental results and providing the superfluid to Mott-insulator quantum convert the atom pairs into ground state guidance for new experiments. phase transition, quantum information molecules using laser light. Finally after

processing, quantum-computing architectures. molecular formation, the Mott-insulator

12 can be "melted" to yield a molecular BEC. Photoassociation in a Using optical tweezers, we trap a pair of Specific calculations have been done for Bose-Einstein Condensate microspheres, one coated with an antigen the homonuclear species ^^Rbj and the and the other coated with the correspon- We have investigated the photoassocia- heteronuclear species KRb. ding antibody, and bring them close tion of atoms (two colliding atoms enough to each other that they repeatedly absorbing a photon, forming a molecule) collide due to thermally driven motion. in a trapped, sodium BEC. We measured By monitoring the position of the trapped, a rate coefficient that exceeds the classical antigen-coated microsphere, we can limit by more than four orders of magni- observe single antigen-to-antibody bind-

tude. The measured rate coefficient is, ing events in real time. We also measure however, in good agreement with results the single molecule, spontaneous dissocia- from a quantum-mechanical two-body tion rate and the average rate at which scattering theory. Classically atoms have antigen-antibody pairs unbind due to + to be next to each other to form a mole- Atoms thermal fluctuations. By varying the cule, but quantum mechanically the BEC number of antigen-to-antibody bonds has a single wavefunction for all the atoms Figure 1 . Schematic showing two-color forma- that can form in a collision, we can tion of molecules in their ground electronic extending over the entire trapped gas. observe cooperativity in the binding. We state by Raman Photoassociation. In a BEC observe not only positive cooperativity, This is another example of how the quan- this process is initially coherent and leads to tum world can give remarkably different but also negative cooperativity (which is a wavefunction that is both atoms and rarer in nature) depending on how rigidly molecules. results than the classical world. Such studies

are important for developing theories that the antigen molecule is attached to the

describe the BEC. The theories can then microsphere surface.

Studies of atomic BEC systems have be used to exploit the BEC as a source of CONTACT: Dr. Kristian Helmerson proven to be extraordinarily fruitful, with atoms analogous to the source of photons (301) 975-4266 connections to a number of disciplines, from a laser for use in precision measuhng [email protected] including atomic, molecular, and optical devices, such as atom interferometers. physics, quantum optics, condensed-matter physics, solid-state physics, quantum CONTACT: Dr. Paul Lett Patterned Loading of Atoms (301)975-6559 field theory, and quantum information into an Optical Lattice [email protected] and computing. One of the primary Quantum systems, such as individual purposes of the Mott-lnsulator transition atoms, can be used as bits of information. is the initialization of a neutral-atom of Real-Time Measurements The processing of such information, gov- quantum register for quantum computing. Antigen-Antibody Binding erned by the rules of quantum mechanics, The production of molecular BECs will is called quantum computing. There is Adhesion is an ubiquitous process in bio- extend applications to molecular species. currently great interest in realizing a logical systems. We have developed a new Experiments along some of these lines is predicted technique to study the adhesion of bio- quantum computer, which are being planned. to require exponentially less effort than molecules in real time under biologically

similar to the situation a classical computer to solve certain CONTACT: Dr. Carl Williams relevant conditions, large-scale problems, such as factoring (301) 975-3531 when two cells collide and adhere. [email protected] large numbers.

13 We are developing a processor for quan- second strategic element is to develop advanced tum infornnation, using neutral atoms The optical and x-ray measurement techniques for applica- trapped in an optical lattice as the quan- tum information register. In an optical tions involving laboratory and space plasmas, thin-film lattice, atoms are trapped in the periodic structures, and nanoscale devices. intensity pattern formed from the interfer- ence of intersecting laser beams.

Plasma and X-Ray We work with x rays since their weak interactions make them a nearly ideal Measurement Methods WWVWl Patterned Loading penetrating probe. The primary goals INTENDED OUTCOME AND of this research are the development BACKGROUND and application of high-resolution x-ray scattering techniques, the production of This strategic element focuses on the use reference samples of thin-film and multi- of atomic radiation as an efficient, non- layer structures, and the understanding interfering probe of plasmas and industri- of the microstructure of thin-film and ally important materials. Our research Figure 2. Diffraction pattern showing the con- multilayer structures appropriate to the includes sizable plasmas used for etching trast between atoms coherently loading into semiconductor industry. every third lattice site, versus every lattice site. semiconductor wafers, small-scale plasmas

confined in electromagnetic traps, and Following on our experience fielding a

nanoscale plasmas induced on surfaces by high-energy, curved crystal spectrometer

In order to achieve the best performance individual, highly charged ions. Information at the OMEGA laser facility at the for quantum information processing, we is obtained by measuring the emitted University of Rochester, we are presently would like atoms tightly confined, which photons and massive particles using a producing a more ambitious, broadband, can be achieved with a short-pehod opti- variety of instruments, including visible, multichannel x-ray spectrometer system cal lattice. However, to initialize and read ultraviolet, and x-ray spectrometers, for the National Ignition Facility (NIF). out the quantum register, we would like microcalorimeters, mass spectrometers, These types of instruments will serve the atoms in sites spaced more than an opti- submillimeter wave detectors, and spatial plasma-diagnostic community by provid- cal wavelength apart. We have taken a imaging systems. In addition, surface ing information about such things as the major step towards achieving this goal by effects are analyzed at the atomic level hot-electron energy distribution and the loading every third site of a one-dimen- using a scanning tunneling microscope plasma temperature. sional, short-period optical lattice with and an atomic-force microscope. atoms from a rubidium Bose-Einstein Our plasma diagnostic research includes condensate. collaborations with industry, university,

and government partners. For example, CONTACT: Dr. James (Trey) Porto (301) 975-3238 Intel and International SEMATECH have [email protected] requested that the NI5T electron-beam

ion trap be utilized to assist in the devel-

opment of EUV lithography light sources.

14 The NIST team continues to work on An effort to characterize many materials

developing a new crystalline nnaterial that and samples is being pursued to see if a scaling factor can be established which does not exhibit birefringence at 157 nm reliably provides the 157 nm values from as one approach to ameliorate this prob- the much more easily measured visible lem. This material is based on mixed solid wavelength values. solutions of CaFs and SrFj, which sepa-

rately have opposite signs of the effect. CONTACT: Dr. John Burnett

Working with industrial partners for (301)975-2679 [email protected] material growth, this new material is

being grown and characterized.

To establish the properties of this and Ion-Gas Recombination Studies

other UV materials, NIST has developed Motivated by a growing interest from the Figure 3. Reflection-geometry spectrometers a unique phase-shifting interferometer constructed as a National Ignition Facility fusion-energy and astrophysics communi- measure the index homogeneity plasma diagnostic (top). Four convex, curved that can ties, we have expanded the NIST Electron crystals (bent to five inches radius of curvature) and birefringence at wavelengths Beam Ion Trap facility to allow ion-gas together provide cascading high-resolution ranging from the visible through 146 nm collision studies. We have installed a gas- x-ray spectral coverage from 1 keV to 20 keV. (in the vacuum ultraviolet). It has enabled jet target and additional detectors on our The four crystals shown (bottom) are a determination of the dispersion of ion beamline to study the photons that Potassium Acid Phthalate, Quartz, Silicon, these properties in this complete are emitted as the ions traverse the target. and Germanium. wavelength range. The new apparatus has yielded measure-

ments on a sequence of charge states of ACCOMPLISHMENTS [001] krypton, starting at Kr^'* and extending through Kr^^*. The study reveals systematic

Optical Properties in Support changes in x-ray wavelength and intensity of UV Lithography ratios as a function of ion charge state.

Particularly dramatic is an abrupt increase, Optical-lithography technology is growing by a factor of two, in the La/M ratio as to more rely upon deep- and vacuum- the L-shell changes from single vacancy ultraviolet radiation in order to further to multiple vacancy. A time-dependent extend the performance of advanced collisional-radiative model of the excited- integrated circuits. This necessitates the state population distribution confirms that use of crystalline fluoride materials for the the origin of this shift is the formation of refractive optics, though little was known Figure 4. Directional dependence of the spa- metastable states. of the optical properties of these materials tial-dispersion-induced birefringence in calcium at these short wavelengths. fluoride and related cubic materials, first calcu- CONTACT: Dr. John Gillaspy lated and measured as part of this project. The (301)975-3236 In May 2001, we uncovered a very large, figure shows the previously-unknown heptaxial [email protected] completely unexpected intrinsic birefrin- behavior (seven nonbirefnngent axes) for this gence in calcium fluoride at short wave- cubic system. lengths. 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.

15 Detection of Chemical

Contamination in a Semiconductor Plasma- Etching Reactor

High resolution, submillimeter wave- length, linear-absorption spectroscopy has been developed as a tool for monitoring chemical contamination in plasma-etching I I reactors. Contamination may arise from OK 1000 K 2000 K 3000 K 4000 K 5000 K 6000 K 7000 K 8000 K 9000 K 10,000 K feed-gas impurities, vacuum-chamber Figure 6. Temperature distribution in a high-pressure lighting discharge as revealed by x-ray leaks, and incomplete chamber cleaning. absorption imaging. The submillimeter methods are particularly sensitive to contamination originating from water vapor, which has an intense demonstrated sensitivity levels less than These processes are so complex that they rotational transition at 557 GHz.

10 nmol/mol. Levels less than 1 nmol/mol have defied attempts at predictive model-

should be possible. ing or even the development of scalable

design rules.

CONTACT: Dr. Eric Benck (301) 975-3697 As part of a cooperative program with

[email protected] the Electric Power Research Institute, NIST

researchers have used x rays from the

Advanced Photon Source at Argonne Powerful Probe for A New National Laboratory to develop a new

High-Efficiency Lighting generation of diagnostic methods for

There are an estimated one billion plasma metal-halide lamps. Both x-ray absorption

light sources in service in the United and x-ray fluorescence were used to map

States, consuming an estimated 2 exa- the distribution of the temperature and

joules (600 billion kilowatt-hours) of the various elemental components in a

electrical energy annually. These sources production-style lamp.

Figure 5. The GEC RF Reference Cell, a are principally fluorescent lamps and The use of these techniques will enable standardized plasma source designed to metal-halide discharge lamps. In the past, lighting scientists and engineers to create plasmas similar to those found in metal-halide lamps were used mainly for commercial semiconductor etching reactors. develop a more complete understanding high-intensity lighting of large spaces. of metal-halide arc lamps, leading to Now, because of their high brightness improved design rules, advanced produc- We have measured this rotational transi- and energy efficiency, they are also being tion methods, and eventually, more tion in a Gaseous Electronics Conference developed for automobile headlights and energy-efficient lighting. (GEC) reference cell, installed at a com- interior lighting. mercial company under three different CONTACT: Dr. John Curry reactor conditions prior to initiating a As a result, there is a growing interest (301) 975-2817 fluorocarbon plasma. The apparatus has in increasing their luminous efficiency [email protected] through a better understanding of

the processes that govern their operation.

16 The third strategic element is to advance measure ment science at the atomic and nanometer scale, focusing on ultraprecise length-displacement measure- ments, x-ray and gamma-ray precision metrology, and

nanooptics and nanosystems modeling. T" I I ~T- 500 600 700 800 900 1000 Wavelength [nm]

crystals. Diffraction angles are measured Nanoscale and Quantum Figure 7. Tapered optical fiber shifts the fre- interferometrically or with well-calibrated quency spectrum of mode-locked femtosecond Metrology For encoders. lower-precision measure- laser output from 850 nm to cover most of

ments, curved crystals are used with INTENDED OUTCOME AND the visible spectrum. The vertical scale is linear; BACKGROUND position-sensitive detectors. the scales for input and output are different.

Optical and x-ray interferometry is being used to complete the intercomparison Figure 7 shows the spectrum from a phase in displacement interferometry. We ACCOMPLISHMENTS fiber whose diameter had been reduced are measuring the effect of diffraction on from 125 pm to 2.7 pm and which was Optical Fiber Tapering interferometric measurements through pumped at 850 nm. We have successfully for comparison of Michelson and Fabry-Perot System Supercontinuum observed the beat from such a fiber and interferometry. We are evaluating a hybrid Generation a helium-neon laser at 633 nm. positioning system in which long-range The frequency comb produced by a positioning over 50 mm is provided by a CONTACT: John Lawall mode-locked femtosecond laser has revo- high-quality commercial translation stage, (301) 975-3226 lutionized optical-frequency metrology [email protected] and guiding errors are compensated by a and is now being applied to displacement fine positioning stage incorporating a metrology. In order to relate the visible multichannel closed-loop servo system. wavelengths used for interferometry with Designing the Nanoworld: We are also working on the direct link of an infrared femtosecond laser, we shift Atomic-Scale Simulations a displacement measurement to a cesium the spectrum of the femtosecond laser by of Nanostructures and clock by means of a frequency comb. The means of nonlinear optics in a fiber that Nanodevices goal is to provide the first measurement is tapered to such a small diameter that of a displacement directly related to the Atomic-scale simulations of the electronic the light propagates in the exterior of definition of the meter, without the inter- and optical properties of complex the cladding rather than the core. vention of a calibrated reference laser. nanosystems at the meso/molecular inter-

facility taper We have constructed a to face are being carried out. These systems The wavelengths and energies of x- and optical fibers to a well-controlled geome- include nanocrystals, self-assembled dots gamma-ray transitions are determined for facility consists of four stepper- try. The (as shown in Fig. 8), nanodot arrays and applications in crystallography and x-ray motor-driven stages that simultaneously solids, molecular electronics, biomolecules, astronomy, for fundamental studies of the pull the fiber as it is being heated by a and bio/nanohybhds. properties of matter, and for the funda- very small, traveling flame. By controlling mental constants. Crystal diffraction is the oscillatory motion of the flame as the the principal measurement tool, and the fiber is pulled, we can force the fiber to lattice spacings of nearly perfect crystals adopt almost any arbitrary shape. are determined by comparison to standard

17 Atomic-scale variations in geometry, size, fourth strategic element is to produce reference shape, and composition critically impact The the functionality of these nanosystems. data on atomic structure and to critically compile For example, our simulations show that reference data for scientific and technological applications. the optical response of arrays of nanodots can be turned on or off simply by chang- ing the number of atoms between the Critically Evaluated ACCOMPLISHMENTS dots. Our studies of doped fullerenes show that dopants exist for p- and n-type Atomic Data New X-Ray Wavelength Table doping, that these doped fullerenes can in Review of Modern Physics INTENDED OUTCOME AND be combined to form molecular rectifiers, BACKGROUND important experimental and theoretical and that their properties can be tailored developments in the field of x-ray transi- The objective of this strategic element as dopant atoms are added one-by-one. tions have made the mid-1960s database is to critically compile fundamental of these transitions obsolete. On the constants and atomic spectroscopy data experimental side, x-ray wavelengths can from the far infrared to the x-ray regions. now be more accurately linked to optical We disseminate these reference data on wavelengths and the SI definition of the Physics Laboratory website, produce length, through combined x-ray and optical high-quality data for urgent scientific or interferometry. In addition, a number of technological needs, and resolve discrep- recent, accurate x-ray measurements, and ancies in the body of the data. updated values of the fundamental physi-

The NIST databases for atomic spectra cal constants, are available to be included

and fundamental constants are recog- in the database. On the theoretical side,

nized throughout the world. The Atomic there has been continued development of Figure 8. Schematic of a self-assembled Spectroscopic Database on our website better calculational procedures that pro- pyramidal quantum dot. Atomic positions now receives about 80,000 downloads duce results in excellent agreement with used in the modeling are indicated. per month, up from 60,000 only two experiment. This good agreement creates

years ago. The principal users are plasma the possibility that theoretical values can

These simulations provide benchmarks physicists, crystallographers, astronomers, provide rather good estimates of missing for precision experimental tests of the lighting engineers, and spectrochemists. or poorly measured experimental data. atomic-scale sensitivity of nanosystems. However, the databases are still far from In collaboration with theorists in France The work is providing the foundation need- complete, and the quality of the data avail- and Sweden, we have produced a new ed to build design tools for engineering able in the literature from which the data- reference x-ray wavelength table that is nanolasers, detectors, biomarkers and bases are built is uneven. The current ver- being published in Reviews of Modern sensors, quantum devices, and nanomaterials. sions of our databases are not sufficiently Physics. The new table is the culmination

reliable for some fields of science and tech- of a long-term NIST effort to produce an CONTACT: Dr. Garnet Bryant nology, and needs for such reference data improved, comprehensive data resource (301) 975-2595 [email protected] are continuously growing. Our scientists for x-ray transition energies. It contains

focus their resources on the most urgent

needs of the user communities. When accu-

rate, reliable data do not exist for high prior-

ity needs, specific measurements or calcula-

tions are undertaken to produce them.

18 K- and L- x-ray transition and absorption This handbook will be published in stan- on the Hubble Space Telescope. The high edge energies for all elements from neon dard paper format, in an e-book that accuracy of these measurements relied on to fermium. It includes carefully selected combines ease of use and portability, and a specially designed system to illuminate and evaluated experimental data robustly in an electronic version on the Physics the spectrometer in such a way as to connected to the SI definition of length, Laboratory website. eliminate small shifts between the spec- and accurate, state-of-the-art theoretical trum of the lasing lines and that of the estimates. The new x-ray wavelength CONTACT: Mrs. Jean Sansonetti calibration lamp. (301) 975-4725 table will soon be available also on the [email protected] Wavelengths of six lasing lines were NIST Physics Laboratory website. measured to an uncertainty of ±0.0001 nm.

Three of the lines were newly observed CONTACT: Dr. Ernest Kessler Precision Measurement (301) 975-4844 lasing lines. [email protected] of Laser Wavelengtlis for 157 nm Microlitliography CONTACT: Dr. Craig Sansonetti (301) 975-3223 The next generation of microlithography Handbook of Basic Atomic [email protected] tools will be based on a molecular-fluorine Spectroscopic Data laser operating at 1 57 nm. In order to design

To meet increasing needs for reference optical systems for focusing ultraviolet spectral data for neutral and singly-ion- radiation from the laser onto the chip ized atoms, we completed a new data- substrate, the index of refraction of the base of wavelengths, energy levels, and optical materials must be known to high transition probabilities for the most accuracy. Since the index of refraction important transitions in all elements varies rapidly with wavelength, it is from hydrogen to einsteinium. chtical that the wavelength of the laser

also be accurately known. This Handbook of Basic Atomic Spectro- scopic Data lists wavelengths and intensi- To obtain accurate wavelengths for the ties for over 12,000 transitions. Energy laser, we used the NIST 10 m vacuum levels and transition probabilities are given spectrometer to measure the lasing lines for about 2400 of the strongest lines, from a commercial laser in the region

references. for taken from over 400 Data of 1 57 nm. The experiment was conduct- individual elements can be accessed by ed in collaboration with an excimer laser name, atomic number, or atomic symbol. manufacturer, which supplied the laser.

A finding list is available to assist in The spectra were calibrated by spectral identification of possible impurities in lines from a platinum hollow-cathode an observed spectrum. lamp that had been measured by NIST

and used to calibrate spectrometers

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 power, achieves a relative standard uncer- tainty of less than 0.02 %. This will be optical radiation standards based on the SI units. reduced to 0.01 % with the completion

of HACR 2.

and on Photometry and Radiometry, of Optical Radiation The improvements realized by tying the the International Committee of Weights Standards radiometric measurements to a cryogenic and Measures. These comparisons provide radiometer are significant. Recently the an important assessment of measurement INTENDED OUTCOME AND Division's spectral-irradiance scale, as quality and help guarantee the interna- BACKGROUND disseminated by FEL lamps, was converted tional acceptability of our Nation's optical to a detector-based scale traceable to The Optical Technology Division plays a radiation measurements. optical-power measurements performed fundamental role in promoting the use by HACR. The improved detector-based of optical technology by undertaking To ensure unsurpassed measurement scale has led to a reduction of the spectral- research and development to advance the accuracy, the Division's radiomethc scales irradiance uncertainties by a factor of measurement science needed to maintain are increasingly being based on stable, two for ultraviolet and visible radiation, the Nation's primary SI standards for the low-noise, highly linear detectors, and a more significant reduction for candela and kelvin and associated photo- radiometers, and photometers. Their infrared radiation. metric, colorimetric, pyrometric, and absolute responsivities are traceable to spectral radiometric quantities. These optical-power measurements performed These activities in detector-based radiome- standards affect a host of industries, using cryogenic radiometry and a state- try are complemented by new research in from aerospace to lighting, by ensuring of-the-art laser facility, SIRCUS (Spectral source-based radiometry, i.e., radiometry the accuracy and agreement of measure- Irradiance and Radiance Calibrations with based on a source of radiation whose ments between and within organizations. Uniform Sources). Cryogenic radiometry spectral output is absolutely known. This provides the most accurate optical-power new research uses synchrotron radiation A significant part of the Division's activities measurements by directly comparing from an electron-storage hng, the recently includes participation in international optical and electrical power. The Division's upgraded NIST Synchrotron Ultraviolet comparisons of measurements with other High-Accuracy Cryogenic Radiometer Radiation Facility (SURF III), as a source national metrology institutes through the (HACR), the Nation's standard for optical of continuously tunable, intense Consultative Committees on Temperature, ultraviolet radiation.

20 ACCOMPLISHMENTS uses a set of filter radiometers to assign a speed of the electron beam, the angular

temperature to the HTBB. Their spectral- spread is narrowly confined to within a

Detector-Based Radiance and irradiance responsivities are traceable to fraction of a degree of the orbital plane.

Radiance-Temperature Scales the HACR optical-power scale through Narrow-band filtered radiometers, with

the Division's Spectral Comparator Facility spectral responsivities measured to 0.1 % We have reduced the uncertainties of the The spectral-irradiance responsivities are relative uncertainty {k = 2) at the SIRCUS present, source-based, spectral-radiance converted to spectral-radiance responsivi- facility, were used to directly measure the and radiance-temperature scales by ties by an appropriate choice of precision radiation emitted from a tangential source converting to detector-based scales. apertures and measurement geometries. point of the ring, from the near ultraviolet

These scales are tied to an absolute The aperture areas required in the analysis to the infrared. imaging pyrometer (API). We calibrated are determined using an optical coordi- The experiment demonstrated agreement its absolute radiance responsivity at the nate-measuring machine. with theory to within 0.5 %. Such excel- SIRCUS facility, using a tunable, laser- The net result: we demonstrated a lent agreement not only confirms the illuminated integrating sphere as the

detector-based temperature uncertainty Schwinger theory, but it also connects the source of spectral radiance. The spectral of 0.21 K{k = 2) at 3000 K, more than detector-based spectral-irradiance scale, radiance is traceable to silicon trap detec- a factor of six better than the source- based on SIRCUS and cryogenic radiometry, tors calibrated for absolute power respon-

based approach. to the source-based scale of SURF III. The sivity against HACR and a set of apertures study further validates Beamline 3 as a of known area to define the geometry. CONTACT: Dr. Howard Yoon broadband standard of spectral irradiance (301) 975-2482 Measurements performed with API of the for the absolute calibration of optical [email protected] freezing point of a high-emissivity black- instruments and for the calibration of body cavity in contact with molten gold deuterium and FEL incandescent lamps reveal a noise-equivalent temperature as secondary or transfer standards. SURF III as an Absolute of 2 mK (/c = 2) at 1337 K. The total Source of Spectral Irradiance uncertainty of the measurements, about CONTACT: Dr. Ping Shaw An experiment was undertaken to verify (301) 975-4416 1 20 mK {k - 2) at this temperature, is [email protected] due to the combined uncertainties arising that the absolute spectral irradiance from from the radiance-responsivity calibra- the NIST Synchrotron Ultraviolet Radiation

Facility (SURF III) can be predicted using tions, the size-of-source effect, and the Second-Generation long-term stability of the pyrometer. the Schwinger relativistic electrodynamical High-Accuracy Cryogenic model for synchrotron radiation and In concert with the API development, knowledge of the electron-beam energy, Radiometer (HACR 2) we have performed radiance-temperature current, and radius. A second-generation cryogenic radiometer measurements of a 2950 K high-tempera- is under development to further reduce ture blackbody (HTBB), comparing both The study was performed on Beamline 3, the uncertainty in our optical-power conventional source-based and newer recently developed for absolute, source- measurements. The expected factor-of- detector-based measurement methods. based, ultraviolet radiometry at SURF III. two reduction in the power-measurement The source-based approach uses meas- The measurements consisted of character- uncertainty will affect many of the radio- ured radiance relative to a gold-point, izing the angular spread of the radiation metric and photometric scales maintained fixed-temperature blackbody to assign the from SURF III in the direction perpendicu- in the Division and presently tied to the temperature to the HTBB as prescribed lar to the orbital plane of the electron first-generation HACR. by the International Temperature Scale beam. Because of the highly relativistic of 1990. The detector-based approach

21 The new instrument is designed to have The second strategic element is to develop novel a greater dynamic range, from 1 fxW up optical measurement methods for solving problems to 70 mW in power, faster response time, lower noise figure, and improved modular in critical and emerging technology areas. construction. It will be installed in the

SIRCUS facility, providing ready access to measurements in rapid thermal processing, a variety of lasers. These lasers allow a Optical Measurement to develop optical-scattering metrology broad range of wavelength and power Methods for the next-generation wafer inspection levels to be selected for scale transfer to tools, and to develop chemical diagnostic silicon trap detectors, further reducing the INTENDED OUTCOME AND methods for reactive, ion-etching plasmas uncertainties in the measurement chain. BACKGROUND using submillimeter spectroscopy Additionally, the modularity of the detec- The Division strives to improve the accura- Ultraviolet-radiation metrology is being tor section permits new detector modules cy acceptability and utility of optical developed to ensure a measurement to be designed and built, optimized for measurements by conducting long-term, infrastructure for 1 57 nm and shorter- specific wavelengths and power levels. directed research in the NIST strategic wavelength lithography leveraging the focus areas of homeland security nan- CONTACT: Dr. Joseph Rice unique ultraviolet-radiometry capabilities otechnology and health care, and in (301) 975-2133 of SURF III to target needs in optical- such promising technology growth areas [email protected] materials properties, detector radiation- as interface science, biophysics, semicon- damage characterization, and laser-power ductor manufacturing, and quantum measurements. communication.

In response to recent events, our support In the areas of nanotechnology and inter- of optical-radiation measurements for face science, we are developing linear and homeland security has increased, building non-linear laser and near-field techniques on expertise developed through the NIST to characterize thin-films, surfaces, and Director's competence program in THz interfaces important in molecular biology, Metrology We are investigating femto- polymer science, and nanotechnology second-pulsed THz spectroscopy for the

detection of biological-warfare agents in In biophysics and heath care, new optical methods based on surface-enhanced paper envelopes that are effectively trans-

parent in the THz spectral region, and Figure 1. Jeanne Houston and Joe Rice Raman spectroscopy and confocal, flu- preparing to calibrate a silicon-photodiode spectroscopy for orescent, imaging microscopy are being continuous-wave THz trap detector using our second-generation the sensitive detection of chemical- developed for the investigation of single, High Accuracy Cryogenic Radiometer, HACR 2. warfare agents. biological molecules. This is part of a larger,

inter-laboratory competence program We are also using our unique expertise in in Single-Molecule Measurement and correlated-photon radiometry to develop Manipulation, funded by the NIST Director. novel, single-photon-on-demand sources

for secure quantum cryptography in The Division's activities in support of semi- collaboration with other PL Divisions. conductor manufacturing include research

to improve the accuracy of temperature

22 ACCOMPLISHMENTS To assess the measurement uncertainty of tethered to a glass substrate in an aqueous the diameter of the particles, the effects buffer solution. The sharpened tip of a

Optical Scattering by of non-sphericity, size distribution, and microfabricated cantilever, with Alexa-488

Nanoparticles on Si Wafers doublet formation were investigated. antibodies attached by 200 nm long poly-

The modal diameter of the 100 nm poly- mer tethers, is positioned over the dye- Light-scattering metliods were developed

styrene sphere standard (SRM® 1963) prepared surface. As the tip is lowered to allow accurate measurement of the was determined to be 99.7 nm with an onto the surface, the cantilever deflection diameters of standard reference particles

uncertainty of 1 .7 nm (k = 2), in excellent and the laser-driven single-molecule fluo- bound to silicon substrates. This was in agreement with aerosol measurements. rescence from the surface dye molecules response to the semiconductor industry's

are monitored (Fig. 2). At some time during need for improved metrology of particles The technique is presently being incorpora- an approach, an Alexa antibody may bind and other defects on silicon wafers. The ted into semiconductor industry standards. to an Alexa dye molecule, quenching its identification and quantification of such fluorescence. The shape of the force curve defects are required to facilitate the trans- CONTACT: Dr. Thomas Germer and the recovery of fluorescence verify fer of wafers from the factory to the chip (301) 975-2876

binding as the cantilever is retracted and manufacturers, and to locate and diag- [email protected]

the bond is broken. nose problems in the chip fabrication line.

Force assays are widely used in biology To calibrate inspection tools, and thus Single-iVlolecule Optical to elucidate binding and folding dynamics to assure agreement between the wafer Probe of Binding in of proteins and DNA or RNA. The addition and chip manufacturers, the industry Antibody-Antigen Force of independent, optical verification of intentionally deposits accurately-sized, Measurements single-molecule binding helps distinguish polystyrene spheres onto reference As part of a NIST-wide competence true binding events from other interac- wafers. Because the deposition process program in Single-Molecule Measurement tions that commonly interfere with can lead to changes in the size distribu- and Manipulation (SM^), we are developing these assays. tion of the particles, techniques are sensitive, single-molecule, spectroscopic required to accurately determine the and imaging techniques for incorporation CONTACT: Dr. Lori Goldner diameters of the deposited particles. (301) 975-3792 into MEMS-based, molecular-screening [email protected] To address this need, we did a combined platforms. theoretical and experimental investigation Figure 2. (A) Fluorescence image of single One technique recently developed uses of the optical properties of subwavelength- Alexa dye molecules on glass. (B) Illustration of single-molecule fluorescence spectroscopy diameter spheres on surfaces. The a simultaneous force and optical data sequence, to monitor atomic-force measurements. Bobbert-Vlieger theory of light scattering showing how cantilever deflection changes as Individual Alexa-488 dye molecules are by a spherical particle on a flat substrate the tip approaches, binds, and retracts. was extended to account for films on both the substrate and the particle, (A) (B) and then validated by measurements Cantilever Deflection on deposited, polystyrene and copper (Force) nanospheres. The copper spheres provid- Fluorescence ed a particularly demanding test of the (Photon Counter) theory due to the presence of a strong near-field interaction between the con- 2 |jm ducting spheres and the silicon substrate. Approach Bind & Contact Unfold Quench

23 In situ Nonlinear Vibrational carbon atoms, C4 and C5, linking the Continuous-wave and pulsed THz spectra Spectroscopy for Biological double ring of the purine. were recorded for a large number of amino acids, peptides, sugars, carbohy- Interfaces The dependence of the amplitude of DR- drates, and vitamins at room temperature In collaboration with CSTL, Doubly SFG features on the polarization direction and at liquid-helium temperature. The Resonant Sum Frequency Generation of the laser beams will permit the spatial complex spectra reveal distinct absorption orientation of the (DR-SFG) spectroscopy is being developed molecules to be deduced. features and patterns that provide infor- as a sensitive molecular probe of biologi- The method is being extended further mation on the molecular conformations cal interfaces important for biosensors, into the ultraviolet to 200 nm to allow and the vibrational and intramolecular DNA arrays, tissue-engineering research, the investigation of peptides and proteins. force fields. and the understanding of cell-membrane CONTACT: Dr. Kimberly Briggman structure and function. A collaborative study with the NIST Center (301) 975-2358 for Neutron Research and the Institut The method relies on the enhanced non- [email protected] Laue-Langevin in Grenoble, France, is linear mixing of infrared and ultraviolet or attempting to interpret these spectra, visible laser beams at an interface when building on a previous, successful model- T3 both lasers are resonant with molecular ing of the neutron-scattering, vibrational transitions, typically a vibrational transition spectrum of crystalline glucose. for the infrared laser and an electronic transition for the visible or ultraviolet laser. The unique signatures of these biological

Femtosecond laser technology and nonlin- molecules has led to an effort to use THz ear optics are used to generate spectrally spectroscopy for identifying chemical- and

broad, infrared pulses between 2.5 pm and biological-warfare agents in paper and 1440 1480 1520 1560 1600 1640 1680 1720 1760 1800 plastic packaging that is transparent to 12 (jm, which are mixed with picosecond Vibrational Frequency [cm"'']

ultraviolet or visible laser pulses at the inter- THz radiation. We have measured the THz

Figure 3. DR-SFG spectra of DNA bases A, C, face to generate an entire broadband DR- spectra of about one hundred common and G tethered to the surface via a thiolate SFG spectrum at high signal-to-noise ratio. materials and biological samples and com- linkage: Au-S-(CH2)6-Base-Base. piled a modest database for this purpose. The approach was used to measure the This DARPA-funded project is being under- first ultraviolet (270 nm) DR-SFG spectra taken in collaboration with SPARTA, Inc. of DNA base dimers tethered to a gold- Terahertz Spectroscopy coated surface using thiol attachment of Biological Molecules CONTACT: Dr. Edward Heiiweil chemistry. Figure 3 presents DR-SFG (301) 975-2370 Novel THz spectroscopy and imaging spectra of oligomers of the DNA bases [email protected] methods are being developed and adenine (A), cytosine (C), and guanosine demonstrated as part of a NIST compe- (G), all of which have electronic transi- tence program on Advanced Terahertz Single-Photon-On-Demand tions in the 260 nm to 270 nm range to Metrology The methods are being applied Sources for Quantum enhance the SFG effect. The vibrational to characterize the molecular structures, modes were identified by analogy to ultra- Cryptography intramolecular force fields, low-frequency violet resonance-Raman spectra at the The security of quantum cryptography concerted motions, and conformational same 270 nm wavelength. For instance, and communication schemes depends dynamics of biological molecules. the intense feature for adenine near on the use of single photons to carry infor-

1600 cm'^ corresponds predominantly mation. Parametric down-conversion (PDC), to the in-plane stretching motion of the

24 which produces photons in correlated Figure 4. Multiplexed Heralded Photon

pairs, is the basis for one type of single- version of a parametric

photon source. Unfortunately, present down-conversion scheme for producing single-photon sources are generally inca- single photons on pable of producing single photons demand. on dennand with high probability, while Delay Processor simultaneously suppressing the probability

of yielding two or more photons. This

compromises the overall security of the

communication. One reason PDC-based third strategic element is to disseminate optical schemes have this problem is because The they employ photon-counting detectors radiation measurements and standards to industry, which cannot discriminate whether just government, and academia. one or a burst of photons was detected.

In response to the need for an improved, on-demand, single-photon source, we Optical Measurement sensing instruments, for measuring the have proposed a multiplexed version of area of precision radiometric apertures, Services the PDC scheme that allows independently and for determining the absolute optical adjustable probabilities for producing one INTENDED OUTCOME AND power, radiance, and irradiance spectral and more than one photon. The system BACKGROUND responsivities of instruments. New meas- operates by collecting multiple pairs of urement facilities under development The Division builds and maintains world- correlated photons from the ring of include reflected color, emittance, retrore- class optical-radiation measurement facili- correlated photon pairs azimuthally flectance, and ultraviolet spectral irradiance. ties to meet the continued and emerging distributed around the PDC pump-laser needs for standards and specialized meas- The Division strives to ensure the quality propagation axis, as pictured in Fig. 4. urements by government and industry. of these programs by publishing our The scheme allows a single, conventional, These facilities are available to govern- research and measurement methodologies photon-counting detector to better ment and industry customers through approximate a true "photon-number" formal calibration services, special tests, detector, which in turn allows the overall and standard reference materials offered system to better approximate a true through NIST Technology Services or single-photon source. through collaborative research efforts.

A recent experimental test of this concept We maintain facilities for optical-proper- with four channels was successful. ties measurements of reflectance, trans-

CONTACT: Dr. Alan Migdall mittance, and gloss; for photometric (301) 975-2331 measurements including luminous intensity [email protected] and color temperature; and for radio-

metric measurements, including spectral

radiance, spectral irradiance, spectral

responsivity and radiance temperature.

The Division has highly specialized facilities Figure 5. Charles Gibson preparing a black-

for performing low-background radiometric body-radiation source for calibration of

measurements, for characterizing remote- spectral irradiance.

25 as NIST Special Publications or in outside 1.52 New Reference Colorimeter 10"' \ 1 peer-reviewed archival journals, by partici- We have constructed and are presently 10"* pating in measurement comparisons with S 1.50 .\ 5 c testing a new reference instrument for other laboratories, and by maintaining q measuring the reflectance color of o ^ a measurement-quality program. The 2 1.48 \ H— -SIO"* materials. This project CD \ was undertaken Division also aids the dissemination of in response to industry and government good optical-radiation measurement 1.46 200 300 400 500 600- Wavelength [nm] demands for improved color measure- practice by publishing training documents ments and standards, as articulated in and offering formal short-courses in 1.44 the 6* and 7* Reports of the Council for Photometry, Spectroradiometry, and 200 300 400 500 600 Optical Radiation Measurements (CORM). Radiation Temperature Measurements. Wavelength [nm] Improved color standards are required to

Figure 6. Index of refraction of CaFj measured ensure better color matching of products

with the DUV-FTS at SURF III. The solid circles manufactured at different sites. Because

show the measured values, and the solid line ACCOMPLISHMENTS the color of a product often plays a major shows a three-term Sellmeier fit, whose role in its acceptability, color measure- residuals are shown in the inset. High-Accuracy, Deep- ments and standards are extremely Ultraviolet, Index of important to industry. Refraction Measurements Initial results at room temperature on a Our new instrument performs measure-

III at SURF 1 mm thick CaFj sample at wavelengths ments for all possible combinations of between 175 nm and 600 nm are shown A new beamline (BL-5) was completed illumination and viewing angles, including in Fig. 6. The solid circles indicate the at the NIST Synchrotron Ultraviolet the standard 0745° and 67diffuse geome-

measured index values, while the solid tries, allowing the complete characteriza- Radiation Facility (SURF III), equipped with

line is the result of a three-parameter a high-resolution, deep-ultraviolet, Fourier- tion of the reflectance properties of an

Sellmeier fit. The residuals from the fit, transform spectrometer (DUV-FTS) to object. The popular 0/45 measurements shown in the inset, are approximately measure the index of refraction of materials, are highly automated through a sample 5 X 10"*. Comparison to our previous with high accuracy In contrast to the wheel with a capacity for 20 samples, prism measurements on CaFj at 193 nm traditional, prism-goniometer measurement as shown in Fig. 7.

shows agreement within 1 .3 x 10^^ of the refracted angle, the DUV-FTS consistent with the estimated combined analyzes the fringe pattern in the trans- uncertainties in the two measurements. mittance spectrum of an etalon made

from the sample material. Plans are undenA/ay to extend the range

to below 1 57 nm for measuring optical Using independent measurements of the materials important to the deep-ultraviolet sample thickness and fringe order, we photolithography industry. Measurements determined the index of refraction with are also planned on deionized water at uncertainties (- 10"^) similar to that of the

193 nm, which is under consideration for classical prism method. The interferometer immersion photolithography. approach offers significant advantages

over the prism method, including greater Figure 7. Maria Nadal prepares the NIST CONTACT: Dr. Keith Lykke continuous wavelength coverage, speed, reference colorimeter (301) 975-3216 and the ability to measure thin samples [email protected] such as absorbing fluids.

26 We did a complete uncertainty analysis, sensing community to calibrate ship- markings on electrical wires used in aero- considering wavelength accuracy stray- »based radiometers. These, in turn, validate space and military vehicles, in response

light rejection, reproducibility of sample satellite measurements of sea-surface tem- to a request by the Navy for improved

positioning, and signal noise. A critical perature. The radiometer was then sent standards in this area. Although the ultra- aspect of the analysis was the inclusion of to ITT Industries in Ft. Wayne, Indiana, to violet-laser-written markings are immune the statistical correlation between signals measure the radiance of two calibration to fading with age, the gray color of the at the same wavelength and between targets used to verify the calibration of writing reduces the visual contrast relative

reflectance factors at different wave- the NOAA Geostationary Operational to black-ink markings. A high contrast

lengths. The estimated measurement Environmental Satellite (GOES) imagers. level is desirable for these markings to

uncertainties are A£ab < 0-4, where AE^t, A third deployment was made to Los ensure the correct identity of a wire

= 1 is generally taken as the threshold for Alamos National Laboratory, to measure during installation, repair, or maintenance. visual discrimination between two colors. the radiance of blackbody sources in a Writing-contrast values of 60 % or higher

cryogenic vacuum chamber previously are recommended by industry standards.

CONTACT: Dr. Maria Nadal used to calibrate a space-flight instrument However, the measured values for the (301) 975-4632 for the Department of Energy. same wire sample often vary by as much [email protected] as 10 % to 20 %. The success of these deployments has led

to new efforts to improve the calibration Our new reference instrument consists Thermal-Infrared of the TXR and to extend its operational of a well-characterized luminance meter

Transfer Radiometer Verifies range to temperatures below 288 K by with a microscope to measure the lumi-

Radiance Scales Used in performing the measurements in a low- nance on a circular spot of 12 pm diame-

Earth Remote Sensing infrared-background, liquid-Ng-cooled, ter or larger. The wire is illuminated by a vacuum test chamber To do these meas- fiber-optic source with a known spectral To establish the traceability of radiometric urements, the NIST Medium-Background distribution. A three-axis translation stage measurements performed by the remote- Infrared (MBIR) facility was used to under computer control automatically sensing community to NIST's radiometric calibrate the TXR against a high-accuracy scans the wire surface. The computer scales, and to perform on-site calibration cryogenic blackbody in conditions that also acquires and analyzes the data. verifications of critical remote-sensing simulate outer space. The facility allowed The instrument characterization yields an instruments, we have developed the the extension of the TXR radiance scale expanded relative measurement uncertainty transportable Thermal-Infrared Transfer down to 200 K and enabled the evalua- of better than 2 % for typical wire colors Radiometer (TXR). Such traceability helps tion of measurement uncertainties due and sizes. ensure that the measurements undertaken to room-temperature infrared background by this community are of the highest A formal calibration service is being radiation and atmospheric infrared accuracy and can be compared to similar established for both standard wires absorption and emission. measurements performed by other and contrast-measuring instruments.

countries or at other times. CONTACT: Dr. Joe Rice CONTACT: Dr. Yoshi Ohno (301) 975-2133 The TXR was deployed at the University (301) 975-2321 [email protected] of Miami's Rosenstiel School of Marine [email protected]

and Atmospheric Sciences, in collabo- ration with NASA-Goddard, to verify the Wire-Contrast radiance scales of several blackbody Measurement Standards sources used by the sea-surface remote- We developed a new facility to measure

the contrast of ultraviolet-laser-written

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 measurements of brachytherapy sources used to prevent restenosis following standards for radioactivity based on the SI unit, balloon angioplasty the becquerel, for homeland security, environmental, With heightened concern in the U.S. medical, and radiation protection applications. regarding terrorists' attacks using radio-

logical or nuclear weapons, we are lead-

ing a national effort to develop standards

Radioactivity Standards and protocols for radiation instrumenta-

tion for first responders. Initial INTENDED OUTCOME AND efforts BACKGROUND are directed towards four areas:

1) equipment standards and test The Radioactivity Group is responsible methods for hand-held detectors for developing metrological techniques for first responders; to standardize new radionuclides for research, and for exploring applications 2) a testbed for cargo-container and truck inspections for radiological in health care, worker protection, environ- and nuclear materials; mental protection, and national defense.

Figure 1 . Dr. Leticia Pibida adjusting laser A vigorous program is underway to develop 3) radionuclidic forensic methods optics for resonance ionization mass microcalorimetric methods to measure based on mass spectrometry; and spectrometry (RIMS). power from radioactive sources. This work 4) a national quality-assurance system is proceeding in parallel with liquid-scintilla- that supports homeland security needs. tion detector methods based on triple-to- The Radioactivity Group also provides Many tens of thousands of low-level double-coincidence ratio (TDCR) counting. leadership in a national program for radio- radiochemical measurements are made Accurate activity measurements over a pharmaceutical standards. We provide the annually to support environmental reme- broad dynamic range are obtained using national standards for radionuclides used diation and occupational health programs. these two complementary techniques. in 13 million diagnostic procedures and The credibility of these measurements has For ultra-low-level atom counting, we are 200,000 therapeutic nuclear medicine been based on participation in regulation- continuing development of resonance procedures annually in the U.S. This work driven, performance evaluation programs ionization mass spectrometry (RIMS), which has been expanded to include radioactivity of limited scope. The fundamental flaw has applications in nuclear forensics as well as in environmental radioactivity.

28 that the metrology community recognizes the detection system, and to predict advantage for measurements in confined

is that there is a lacl< of direct linkage to the shielding effect of other materials and narrow places, and it has low power

national radioactivity standards. This situa- in the container. consumption. It may be the best choice

tion is being addressed in the publication for monitoring relatively high-level source The goal of this work is to develop a of three ANSI standards. These consensus movement or dispersal. standard container and measurement standards call for a traceability-testing protocol, so manufacturers can calibrate program that links the quality of operational CONTACT: Dr. Leticia Pibida their detectors, and users can develop (301) 975-5538 measurements to the national standards. criteria, for radiological detection in [email protected]

ports of entry in the U.S.

Microcalorimetry for ACCOMPLISHMENTS CONTACT: Dr. Leticia Pibida (301) 975-5538 Absolute Radioactivity [email protected] Cargo-Container Standardizations Inspection System A new, primary standardization capability

The smuggling of materials or weapons Gamma-Ray has been established at NIST to provide

in shipping containers represents a clear Spectrometry System standardizations for rather large, GBq- threat to the U.S. Major radioisotopes of range, brachytherapy sources. In addition Due to increased concerns about a possible concern are predominantly the plutonium to the dual-compensated, cryogenic terrorist attack using radioactive materials and highly enriched (weapons grade) calorimeter operating at = 8 K, a commer- in dispersal devices, we have initiated new uranium isotopes, as well as some of cial "isothermal microcalorimeter" has research in gamma-ray measurements. their fission products, e.g., '°Sr and ^^'Cs. been adapted and evaluated for use in Information about the equipment required These are the key ingredients of nuclear performing classical, calorimetric-based for these kinds of measurements is of fuel and nuclear warheads. The threat standardizations. great importance. also includes radioisotopes primarily used This dual-cell, near-isothermal (heat flow) in industrial and medical applications, Two new CdZnTe detectors were tested, calorimeter operates at near-ambient such as ^"Co, ^"Cs, ^'°Tm, ^"Ir, ^^'1, ''"^Tc, and their ability to detect gamma-ray temperatures, utilizes specially-fabricated '"'Am, and "'Ra. emitting sources was compared with source-holder cells that are used to maxi- existing High-Purity Germanium and We are developing a cargo-container mize the energy absorption of the ionizing Nal(TI) detectors. Because these detectors inspection testbed to provide a means radiation, and incorporates resistance all can operate at room temperature, they for calibrating detectors used for radio- heaters within these measurement cells are attractive candidates for field meas- activity measurements in the field. This to obtain very-accurately-determined, urements. The detectors' efficiency, detec- testbed is outdoors to simulate actual independent, power calibrations. tion limits, and energy resolution were operational conditions. Different kinds measured to determine their performance Evaluations were initially performed on of standard radioactive sources will be and the circumstances under which they two different types of intravascular placed inside a cargo container, so that could be used. brachytherapy sources containing nuclides different kinds of detectors can be tested that decay by pure p emission, viz., and calibrated to optimally detect and The measured energy resolution of the (1) a stainless-steel-jacketed s°Sr-'°Y measure the sources. Computer modeling CdZnTe detector is better than that of the source with a highly-refractory, ceramic- will be used to confirm changes in effec- Nal(TI) detector, but its efficiency is lower, like, inner matrix, and (2) a "hot-wall" tiveness due to possible geometrical mainly due to the smaller crystals that are balloon-catheter source that consists of changes of the sources with respect to presently available in the market. On a thin film of ^^P enveloped between the other hand, its small size can be an

29 polyethylene walls. The measured thermal We have constructed a TDCR spectrometer representatives from NIH, radiopharma- power was related to source activities with three phototubes and the electronics ceutical manufacturers, radiopharmacies, through the use of calculated average to process 2- and 3-fold coincidences of isotope producers, government regulators, energies per decay, and was compared detected photons emitted from the liquid and NIST against known source activities deter- scintillator medium. We measured its mined from previous radioanalytical operating characteristics using solutions destructive assays. Monte Carlo calcula- of NIST SRMs for (tritiated water) and tions for the energy deposition in the "Ni. The TDCR-measured activities agree measurement cells were used to correct with previously certified values to within for power losses due to escaping 0.04 % and 0.2 %. We now can calibrate ionizing radiation. radionuclides encountered in nuclear medi-

cine with shorter sample preparation times This verification work clearly demonstrated, and with less, long-lived, radioactive waste. quantitatively that the "isothermal" microcalorimeter was sufficient for CONTACT: Dr. Brian Zimmerman performing primary calibrations. (301) 975-5191 [email protected]

CONTACT: Dr. Ronald Colle (301) 975-5527 [email protected] Workshop on Figure 2. Michelle Millican preparing radioac- Standards for Important tivity standards for a radiotherapy nuclide.

New Technique for Radiotherapy Nuclide

Absolute Standardization The American Cancer Society estimates Among the concerns expressed by the of Radionuclides that there will be a total of 64,000 new 46 participants were the need for more cases of lymphoma in the U.S. this year, frequent distribution of standards for '"Y Beta-emitting radionuclides make up the with an expected five-year survival rate (currently once a year), a desire for NIST majority of nuclides used in nuclear medi- (for non-Hodgkin's lymphoma) of 52 %. to issue '°Y solution standards in clinically cine. Because of its high detection efficiency, A new drug for treatment of this disease useful geometries instead of the standard liquid scintillation counting (LSC) is the is Zevalin, which is a monoclonal anti- NIST 5 mL glass ampoules, and the need preferred method for calibrating these body labeled with the radionuclide '"Y. to establish measurement traceability for radionuclides. Traditional applications of While has many properties that make an estimated 450 radiopharmacies. NIST LSC require the use of tracers, such as ^H, it suitable for use in radiotherapy, those is working with radiopharmacies, the FDA, and a calculational model to determine same properties present a number of the Society of Nuclear Medicine, the the detection efficiency for the nuclide challenges regarding its measurement. American Pharmaceutical Association, under investigation. The Triple-to-Double and others to organize and implement Coincidence Ratio (TDCR) method is a Anticipating imminent FDA approval of a program that meets these needs. new, quasi-absolute, LSC technique that Zevalin and an exploding need for stan- can determine the counting efficiency dards and measurement quality assurance CONTACT: Dr. Brian Zimmerman for a radionuclide, without the use of for other radiopharmaceuticals using (301) 975-5191 an external tracing standard. this nuclide, NIST held a workshop in [email protected]

December 2001 to address the measure-

ment issues. Invited speakers included

30 The second strategic element is to develop and The primary focus of our polarized ^He program is the development of neutron provide neutron standards and measurements spin filters and application of these needed for worker protection, nuclear power, devices to both neutron scattering and

fundamental neutron physics. We are homeland security, and fundamental applications. developing two optical-pumping meth-

ods, spin-exchange and metastability-

exchange, for producing the polarized Neutron Standards A new, neutron-imaging facility has been ^He gas. We are pursuing applications constructed at the BT6, high-intensity, and Measurements at the NCNR, the Intense Pulsed Neutron thermal neutron beamline at the NIST Source at Argonne National Laboratory, INTENDED OUTCOME AND National Center for Neutron Research and the Los Alamos Neutron Science Center BACKGROUND (NCNR) nuclear reactor. The primary use of this facility will be to non-destructively The Neutron Interferometry and Optics The Neutron Interactions and Dosimetry characterize water-transport mechanisms Facility is a national user facility operated Group lias initiated a homeland-security using real-time imaging of fuel cells. by the group. Radiography and tomogra- program to improve the ability to detect phy services and research involve academic fissile materials in transit. Working with Neutron lifetime and decay-asymmetry and industrial customers and collaborators. the Radioactivity Group, we are creating experiments improve our knowledge of During the past year, analysis of the n-H, a cargo-container inspection testbed at the fundamental nucieon weak couplings n-D, and n-^He scattering-length data was NISI in order to improve our ability to test and may ultimately lead to a significant completed and the time-dependent water commercially developed, homeland-security test of the unitarity of the CKM matrix distribution in an operating fuel cell was neutron detectors. In addition to testing for three generations of quarks. If these non-destructively imaged and quantified. detectors, the group is developing a measurements establish a violation of The success of the fuel-cell imaging drove high-sensitivity neutron spectrometer unitarity then it will provide an important the development of the neutron-imaging for detecting fissile materials in transit. clue to the physics beyond the Standard facility described above. Model of particle physics. The search for Another project with homeland-security a time-reversal-violating asymmetry also Neutron cross-section standards for key, implications, as well as energy and envi- probes physics beyond the Standard fundamental reactions are important ronmental applications, involves imaging Model. We operate three beams at the since almost all neutron cross sections are chemical processes in fuel cells. Compared NCNR to carry out such measurements. measured relative to them. Any improve- to other forms of radiation, neutrons are These include a 0.5 nm monochromatic ment in a cross-section standard leads to highly efficient in probing complex struc- beam, a 0.9 nm monochromatic beam improvement in all measurements that tures. This is because of their tremendous dedicated to ultracold neutron production, have been or will be made relative to that penetration capability in almost all known and a high-intensity polychromatic beam. standard. We have improved neutron materials and their unique ability to distin- cross-section standards through both guish different materials with very similar data evaluation and experimental work, physical properties. They are particularly and are leading an effort that will result effective in detecting hydrogenous materi- in a new international evaluation of als and light elements. neutron cross-section standards.

31 ACCOMPLISHMENTS a liquid scintillator followed by thermal

neutron capture. It uses a segmented

Detection of Nuclear geometry to improve energy resolution.

Materials in Transport This spectrometer is based on a technique

developed for detecting background neu- Spent fuel from nuclear reactors, trons in a neutrino-detection experiment weapons-grade plutonium, and certain

and is expected to have sensitivity of 1 0 weapons-initiator materials emit large % or higher. The energy resolution will be numbers of neutrons from spontaneous optimized for detecting secondary fission fission or (a, n) reactions. These are mate- Less More neutrons from "^U triggered by active rials which terrorist groups could obtain — Attenuation — portal monitors and released through the fairly easily for constructing radiation- n) reaction or fast-neutron activation. dispersal weapons or fission weapons. (y, Figure 3. Image of water transport in an

Because U.S. borders are easily crossed operating fuel cell obtained by neutron CONTACT: Dr. David Gilliam in many wilderness areas, and because transmission radiography. (301) 975-6200 these materials could be obtained from [email protected] sites within the U.S., it is not sufficient to inspect baggage and cargo at points Because the quantification of time- of entry. Advances in Neutron dependent water distribution is a critical

tool in theoretical modeling of fuel-cell Imaging of Fuel Cells Very sensitive neutron detectors coupled water-transport characteristics, and with surveillance cameras could be posi- Neutron imaging is ideally suited for because our capabilities are unique in the tioned at highway chol

tent with observed periodicity).

32 Prospects for an Improved The advantages of this technique over techniques. The cell was polarized off-line Measurement of the Neutron previous experiments are: continuous and used on the beamline in the absence detection of scintillations from decay of optical pumping. The polarization life- Lifetime: Magnetic Trapping electrons, and the elimination of wall time of the cell is 550 h, which is close to of Ultracold Neutrons losses and betatron oscillations. Analysis the theoretical limit set by dipole-dipole

Recent success in magnetic confinement indicates that systematic errors due to relaxation. A compact, magnetically- of ultracold neutrons in an loffe-type neutron losses should be controllable shielded solenoid permitted a relaxation magnetic trap should 0'^ superconducting to 1 T„. A measurement of at the time of 350 h on the NG1 instrument in lead to an improved measurement of 10"^ level of statistical accuracy should the presence of stray fields from a 0.6 T the neutron lifetime t^. be possible, given the flux available magnet at the sample position and guide

from the NG6 beamline at the NCNR. field magnets. The trap is loaded through inelastic scat- tering of 0.89 nm neutrons with phonons The efficiency of ^He spin filters depends CONTACT: Dr. Paul Huffman in superfluid ''He. Trapped neutrons are (301) 975-6465 strongly on the achievable ^He polariza- detected when they beta decay. Energetic [email protected] tion. We have reproduced a value of decay electrons ionize helium atoms in 70 % polarization that the University of the superfluid, resulting in efficient con- Wisconsin had obtained with a unique, Neutron Spin Filters version of electron kinetic energy into optical quality, long-lifetime cell provided light (scintillation). The changing rate of Based on Polarized ^He by us. We have also duplicated the spec- neutron decays in the trap is proportional Notable progress has been made in trally-narrowed, high-power diode laser to the number of neutrons in the trap. developing and applying neutron spin developed at Wisconsin, which has partic-

To the extent that this population is ular relevance filters based on polarized ^He gas. We to the size and pressure changing only by the beta-decay of the continue to employ two optical-pumping ranges of neutron-spin-filter cells. In large trapped neutrons, the rate of detected methods, spin-exchange and metastability- spin-filter cells, we have obtained 55 % neutron decays will decrease exponentially exchange, to produce the polarized gas to 65 % 'He polarization with both with a lifetime of x^,. for applications in both neutron scattering broadband lasers and the spectrally

and fundamental neutron physics. narrowed system, but the much higher

efficiency of the narrowed system will Specular reflection tests using a polarized- permit further improvement with modest ^He spin filter on the NCNR NG1 reflec- laser-power levels. tometer were performed to compare the

use of a ^He analyzer to that of a conven- CONTACT: Dr. Alan Thompson

tional supermirror analyzer. The ^He cell (301) 975-4666 [email protected] was 6 cm in diameter, and the gas was

polarized to 57 % using spin-exchange

Figure 4. Students in Guide Hall at experiment

station for magnetic trapping of ultracold

neutrons.

33 The third strategic element is to develop dosimetric calibration laboratories. NIST maintains more than 75 beam qualities for conven- standards for x rays, gamma rays, and electrons tional, W-anode, x-ray beams, and 17 based on the SI unit, the gray, for homeland security, beam qualities for mammographic.

Mo- and Rh-anode, x-ray beams. medical, radiation processing, and radiation protection applications. The radiation-transport and Monte Carlo methods pioneered and developed at NIST

to calculate the penetration of electrons Radiation Dosimetry photon-emitting seeds to treat prostate and photons in matter are used in most cancer and in the use of beta-particle- Standards of the major codes today Monte Carlo (and photon-) emitting sources to inhibit simulation is increasingly applied to prob- INTENDED OUTCOME AND arterial restenosis (re-closing) following lems in radiation metrology, protection, BACKGROUND balloon angioplasty In both cases, NIST therapy and processing as an accurate has responded to the needs of the manu- The Radiation Interactions and Dosimetry tool for designing and optimizing radia- facturers, regulators, and clinical physi- Group promotes accurate and meaningful tion systems and for providing important cists. We develop new standards and measurements of dosimetric quantities insight into processes inaccessible to measurement methods to calibrate the pertaining to ionizing radiation: x rays, measurement. quantities needed to ensure accurate gamma rays, electrons, and energetic, dosimetry for the wide variety of sources positively charged particles. We maintain introduced, and we disseminate these the national measurement standards standards through a networl< of secondary ACCOMPLISHMENTS for the System International (SI) unit calibration laboratories. for radiation dosimetry, the gray Radiation-Sources for More than 600,000 cancer patients per NIST is a world leader in the measure- Medical and Industrial year are treated in the U.S. with radiation ment of high levels of absorbed dose, Applications beams, mainly from high-energy electron as required in the industrial radiation accelerators (either directly with the In addition to a dozen gamma-ray (^"Co processing of materials (e.g., sterilization electrons or by converting them to and ^^^Cs) sources and five x-ray ranges, of single-use medical devices, food high-energy x rays). NIST maintains and NIST maintains the Medical Industrial irradiation, and destruction of biological disseminates the standards for air kerma Radiation Facility (MIRF), along with a weapons). Accurate transfer dosimetry (exposure) and for absorbed dose to 4 MeV Van de Graff and a 500 keV elec- is increasingly done on the basis of water from ^°Co gamma-ray beams. trostatic accelerator. These are used in a alanine/EPR dosimetry, rather than the These provide the basis for calibrating variety of radiation applications, such as radiochromic film dosimetry originally instruments used to measure the material modification, radiation-hardness developed at NIST and offered here for absorbed dose delivered in therapy testing, electron- and bremsstrahlung- many years as a calibration service. A new beams. Standards for diagnostic radiology beam dosimetry, and high-energy NIST system is near completion for on- are developed and maintained at NIST in computed tomography development. demand, Internet-based e-calibrations for terms of air-kerma, for x-ray beams from Design and construction are underway on industry, based on alanine/EPR dosimetry. 10 kVp to 300 kVp (x-ray source acceler- two new accelerator facilities. Installation

Brachytherapy (treatment with sealed ating potential in kilovolts). These are is being completed of a 6 MeV to 20 radioactive sources) has seen a tremen- disseminated to manufacturers and the MeV electron-beam (6 MV and 18 MV dous increase in the use of low-energy. medical physics community in North bremsstrahlung-beam) linear accelerator America through a network of secondary

34 to support the development of direct, and industrial irradiation facilities to This collaboration continues, expanded therapy-level dosimetry calibrations. provide critical dosimetry measurements to include qualitative measurements of

Planning is also underway for a 10 MeV, and to validate the process. radiolytic products produced in the mail

17 kW electron linac to support the stan- during the irradiation, quantitative meas- Based on an extensive program of Monte dards and calibrations program for indus- urements of the effects on the archival Carlo radiation-transport calculations trial radiation processing and the study properties of paper due to irradiation, and accurate dosimetry measurements of radiation effects in materials. and the design of a dedicated USPS in a variety of mail configurations, NIST mail-irradiation facility provided advice for optimizing the process CONTACT: Dr. Fred Bateman parameters and developing a national (301) 975-5580 CONTACT: Mr. Stephen Seltzer [email protected] strategy to effectively handle the highly- (301) 975-5552 variable mail and parcel stream. [email protected] Assistance to U.S. Postal

Service in Decontamination High-Energy Computed of IVIail Tomography (HECT) Facility After anthrax-laced mail was delivered to The 7 MeV to 32 MeV Saggataire linac media and government offices, resulting in the NIST Medical Industrial Radiation in five deaths, numerous illnesses, and Facility (MIRF) offers unique possibilities enormous disruption and economic loss, as an x-ray source for a high-energy we responded rapidly to identify industrial computed tomography facility A beam- irradiation of the mail as an effective and line and camera are under development readily-available process to kill anthrax at MIRF to study the x-ray inspection of spores. Leading a task force established cargo containers, trucks, and other large by the White House Office of Science and Figure 5. NIST test packages to validate radia- objects. are also carrying out theoreti- tion doses needed to decontaminate parcels We Technology Policy, we worked with the for U.S. Postal Service. cal and experimental investigations into Armed Forces Radiobiology Research neutron production in high-energy x-ray Institute, the U.S. Postal Service (USPS), 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 [email protected]

Figure 6. Dose distribution of

sample of irradiated mail.

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 1950, and practical applications have historically always followed these advan- that serve as reference for time-and-frequency services ces, an aggressive program of research and research on advanced measurement systems. and development in this area is easily

justifiable. The Division is developing

frequency standards based on optical under computer control. We are advanc- Time and Frequency transitions that have dramatically higher ing the performance of the time scale by Q factors. These optical standards already Standards acquiring more stable clocks and improv- provide much higher stability and promise ing the electronic systems that read the INTENDED OUTCOME AND orders of magnitude improvement in clock outputs. Such improvements are BACKGROUND accuracy They would not have been critical to the successful evaluation and practical choices, however, without the The intended outcome of this program use of the next generation of primary recent development of extremely stable is the continuous operation of frequency frequency standards. laser oscillators and the means for directly and time standards with the accuracy and connecting their optical outputs to stability essential for supporting U.S. com- The accuracy of the NIST time scale is microwave frequencies. merce and trade. This includes coordinat- derived from the current primary frequency ing our activities with those of other standard, NIST-F1, a cesium-fountain Since the world operates on a unified national standards laboratories. standard with a relative frequency uncer- time system. Coordinated Universal

tainty of 1 fHz/Hz. The Division plans Time (UTC), highly accurate time transfer The NIST time scale provides accurate to build an improved cesium-fountain (to coordinate time internationally) is a time-and-frequency reference for our frequency standard in the near future, critical ingredient in standards operations. services and for research on new stan- designed so as to simplify the process To achieve this coordination, the Division dards and measurement methods. It is of accuracy evaluation. is developing and using several satellite- an ensemble of commercial cesium-beam transfer techniques. standards and hydrogen masers, combined Since the accuracy of frequency stan- dards has improved by more than an

order-of-magnitude every decade since

4

36 ACCOMPLISHMENTS Stimulated by the acquisition of five through the intermediary of a hydrogen hydrogen masers over the last decade maser. The short-term stability of the

Improved Steering of and the development of a more accurate mercury standard is superior to that of

UTC(NIST) to UTC primary frequency standard, NIST-F1 , we NIST-F1, so the maser played a key role

investigated other steering algorithms. in the comparisons. The process of running a national tinne Using old clock data, we found that scale involves periodically steering it The variation in the frequency of the S-D improved time-offset performance could to the international average, that is, to optical transition relative to NIST-F1 was be achieved by increasing the number of UTC. Since UTC is formed by averaging found to be less than ± 1 0 f Hz/Hz over the steers to two each month and by modify- clock data submitted by many institutions, two years. ing the objectives of the steering. The this BIPM-generated paper average, deliv- philosophy for steering was changed from ered on a monthly schedule to all labora- an emphasis on frequency stability only tories, represents the performance of the to one in which frequency stability could time scale at past times. In fact, for a given be degraded slightly to achieve smaller monthly report, the most recent BIPM data F-Y 1-7 time offsets. are at least two weeks old. Each laboratory must have a strategy for accomplishing The result is that UTC(NIST) now typically this steering. 4- deviates from UTC by no more than . 1 , 1 , 1 Aug 00 Feb 01 Aug 01 Feb 02 Aug 02 20 ns, an improvement of better than Measurement Da te Until recently, NIST opted to place a factor of two. maximum emphasis on frequency stability Figure 2. Measurements over two years of the BIPM data arriving mid-month were CONTACT: Dr. Judah Levine frequency of the mercury optical standard rela- analyzed, and a fixed steering rate was (303) 497-3903 tive to the cesium primary frequency standard. determined for the following month. [email protected] For example, the decision might have been to (or to subtract) 1 ns made add The uncertainty of the absolute measure- per day to (from) the scale for the follow- Reproducibility of Optical ment (at this same level) is the most accu- ing month. A decade ago, the noise on Frequency rate measurement ever made of an optical

UTC(NIST) and UTC made it difficult to The mercury-ion optical-frequency stan- frequency and a very encouraging result, steer more carefully than this. dard has the potential for an accuracy since no significant effort had been made

surpassing that of the cesium-fountain to control systematic frequency shifts. The

standard by two or more orders of largest of these shifts is expected to be the

atomic quadrupole shift, which depends magnitude. With a Q factor greater than on the ohentation of the applied magnetic 10'" and a transition that is relatively

field relative to ambient, static electric-field insensitive to environmental factors, the gradients. Concepts for determining and potential uncertainty for the standard is

controlling this and other smaller shifts as small as 1 aHz/Hz (0.001 fHz/Hz). have been developed, but further studies The reproducibility of this standard relative are needed to test them. to the present cesium standard (NIST-F1)

was studied over a two-year period. CONTACT: Dr. James Bergquist Measurements were referenced to NIST-F1 (303) 497-5459 [email protected] Figure 1. Judah Levine and Tom Parker

discussing strategies for time-scale steering.

37 Improved Calcium Having achieved 10 pK, we turned off Frequency Standard the three-dimensional cooling lasers and reapplied a pulsed version of one-dimen- Because the Doppler-cooling limit for sional QNLC cooling to the already-cooled calcium is 2 mK, the uncertainty in atoms. This reduced the temperature even frequency measurements of the 657 nm lower, to 300 nK. This suggests that even transition are limited at about 10 Hz by further cooling is possible and that the the residual motions of the atoms. Thus, calcium optical-frequency standard has second-stage cooling is needed to improve much greater potential than previously this as an optical-frequency standard. recognized.

Last year, we reported a concept for CONTACT: Dr Chris Gates achieving sub-Doppler cooling, called (303) 497-7654 quenched narrow-line laser cooling Figure 3. The calcium optical-frequency [email protected] (QNLC), and demonstrated it in one standard being adjusted by Chris Oates. dimension. This year, we extended our system to three dimensions.

The three-dimensional cooling relies on The second strategic focus is to develop and operate the same basic principal, but uses simulta- the frequency and time services essential for synchro- neous rather than sequential excitation for the three-level system (clock and nizing important industrial/commercial operations and quenching transitions). A frequency- supporting trade and commerce. doubled diode-laser system generates the light at 423 nm used for Doppler cooling. The second-stage cooling Time and Frequency The Division provides timing broadcasts requires an additional beam at 552 nm from stations WWV and WWVB in Fort for the quenching transitions. Services Collins, Colorado, and from WWVH in

Hawaii. WWVB has a broadcast power With these methods we reduced the aver- INTENDED OUTCOME AND of 50 kW. It is substantially more useful age atom velocity by a factor of 1 5 and BACKGROUND for mobile and consumer applications lowered the temperature to 10 atom pK. The intended outcome of this program is because the antenna/receiver cost and At this temperature, the frequency shifts the reliable delivery of frequency-reference size are very small. due to motional effects are < 1 Hz at the and time-reference signals to the United clock transition, 456 THz. Further improve- States to support industry, trade, science, We also operate telephone-based and ments should reduce the frequency uncer- and the general public. The telephone Internet-based time services. We provide tainty due to motions to < 0.4 Hz, which system, the Internet, radio broadcasts, a telephone audio service and a modem- corresponds to relative a uncertainty of and satellites are all used to deliver these based Automated Computer Time Service less than 1 fHz/Hz. signals. We serve a broad range of systems (ACTS). On the Internet, our 14 servers

in business, telecommunications, science, at 1 1 sites respond to all three common

transportation, and radio/TV broadcasting. transaction protocols. Usage now exceeds

one billion transactions daily.

38 Industrial calibration laboratories are WWVB Time Broadcasts served by the Division's Frequency Recognizing that there has been a Measurement Service, a system that pro- tremendous expansion in the number of vides these laboratories with continuous consumer products based on the WWVB assurance of the accuracy of their time broadcasts, we made a variety of frequency measurements. The most improvements to the broadcast systems demanding applications are served by the 9/1998 9/1999 9/2000 9/2001 9/2002 during the last year. These were made Division's Global Time Service, which uses Sample Date as part of a long-term plan to assure GPS common-view time transfer to deliver continuity of operation of this service. to the user's site a timing reference close Figure 4. Growth in use of the NIST Internet

Tinne Service. in accuracy to that of the NIST time scale. New insulators were installed at the

ground level of all of the guy wires To enhance U.S. expertise in this field, supporting the eight antenna towers. the Division offers a variety of training To deal with this continued growth, we These insulators are designed to be fail- courses. A3'/2 day metrology seminar is initiated two new projects this year. The safe and retain their mechanical integrity offered annually, and we co-sponsor an first involves the use of switches (routers) even if the insulator should break. This annual workshop on synchronization in that will be used to load-balance among will prevent the sort of tower damage telecommunications systems. Additionally, the 14 time servers, since some servers experienced several years ago when one NIST staff members teach courses at are near saturation while others are expe- of the guy-wire supports failed completely conferences. riencing only modest use. Four switches due to an insulator failure. These caused were purchased and successfully tested. substantial damage to the tower. They will be installed soon.

A secure climbing line was added to ACCOMPLISHMENTS The second project, which is only now each of the 1 20 m towers to comply with getting started, is to implement an OSHA tower-safety requirements. Not NIST Internet Service Time encrypted time-delivery system through only will this assure climbing safety, This service continues to grow rapidly and one or more of the servers, using a but it will also speed maintenance and is approaching a usage level of 1 billion concept we developed and patented. repair activities. hits per day. Downloads of the instruction The objective is to provide the means files for setting up a users' computer are for secure delivery of time signals to averaging 100,000 per month. Conserva- systems operated by industry. tive estimates of the total number of The hope is that there will be a gradual users range as high as 50 million. grov\/th of commercial delivery of time

Efforts continue toward finding ways in signals by companies that are targeting which this service might be operated com- specific market sectors. At this point, we mercially. However, the lack of a means are working with several companies that for efficiently collecting service fees for are interested in delivering time services delivery of a few bytes of transmission to financial traders. serves as a stumbling block.

CONTACT: Dr. Judah Levine (303) 497-3903 [email protected]

39 The old tower beacons were replaced third strategic focus is to develop new measure- with new FAA-approved beacons to The ment systems and methods in support of improve the visibility of the beacons to emerging low-flying aircraft. We plan to repaint the technologies.

towers in the FAA-approved manner to

assure good visibility to aircraft during daylight hours. New Measurement could be done previously Such measure- ments will clearly have impact on wave- Systems and Methods length standards for fiber communications INTENDED OUTCOME AND systems and on absolute length metrology BACKGROUND These same combs are being used to generate microwave outputs from optical- Through this program, the Division frequency standards, essentially providing prepares for the future of time-and- the basis for a whole new generation of frequency measurements and calibrations. atomic standards. Now that the accuracy Through interactions and discussions with of these measurement systems has been NIST constituents, we identify important, established, work involves simplification emerging industrial requirements and and noise reduction. technologies, and develop measurement Figure 5. An aerial view of the WWVB systems and methods designed to meet Another component of this program antenna systems.

their needs. is the measurement of close-to-carrier

noise in oscillators and other electronic NIST has a long history of metrology components. A closely related effort Finally, we designed a field-strength meter expertise and leadership in such areas as: involves improving statistical metrics for the 60 kHz signal and contracted to the non-stationary statistics of clocks and for analyzing such noise. Projects in have a number of these produced for field oscillators; optical-frequency measurement this area will have impact not only on monitoring purposes. These will be placed systems; atomic and optical oscillators; improvements in characterization of clocks at various locations around the country time-and-frequency transfer through and oscillators, but also in telecommuni- to continuously monitor signal strength. satellites; low-phase-noise electronics; cations systems, advanced radars, and The field-strength information will be fed and network synchronization. The ultimate other narrow-band electronic systems. periodically to the station website for use goal is to apply our expertise to carefully by WWVB product manufacturers and selected projects so as to assure continuity Finally, smaller, less-accurate oscillators their their customers. in providing the highest-performance time- play a major role in a variety of measure-

and-frequency services to U.S. industry, ment instruments and electronic systems. CONTACT: Mr. John Lowe science, and the general public. We have often contributed to develop- (303) 497-5453 [email protected] ing and improving such oscillators. The The synthesis and measurement of optical newest program in this area, stimulated frequencies have become a central focus in large part by some of our fundamental in this program. The new optical-frequen- research, is a DARPA-funded program cy combs generated by femtosecond to develop a chip-scale atomic clock, a lasers have provided the means for meas- program involving NIST, several universities, uring optical frequencies at uncertainty and a number of companies. levels orders-of-magnitude better than

40 .

ACCOMPLISHMENTS experiments on this new system, the As a test, the statistic was used over microwave output frequency from a comb the past two years for measuhng the

Improved Frequency-Comb that was phase-locked to a calcium optical- performance of the NIST time scale and

Generator frequency standard (456 THz) was shown the primary cesium-fountain frequency

to have a short-term frequency stability standard, NIST-Fl. One of the key stability/reliability issues 100 times better than that of a hydrogen with the usual frequency-comb generator The results clearly demonstrated the maser. The long-term performance of the involves the microstructure optical fiber efficiency of the statistic. It served to device will depend on how well systematic used to broaden the output of the improve the performance of the time effects in the optical standard are controlled. femtosecond laser to a full octave. The scale and to reduce the time required very high power density required to to evaluate the accuracy of NIST-Fl CONTACT: Dr. Scott Diddams achieve this broadening causes damage (303) 497-7459 to the fiber. It must be adjusted and [email protected] CONTACT: Dr. David Howe replaced periodically (303) 497-3277 [email protected] We recently collaborated with the Institut Statistical Measure for fur Halbleitertechnik (Germany) to demon- Long-Term Stability strate a phase-coherent link from optical Broadly Tunable Microwave The measurement of the long-term to microwave frequencies in a system that Reference Oscillator does not require a microstructure fiber stability of clocks and oscillators has been The measurement of phase-modulation for spectrum broadening. This success is a long-standing problem for science and (PM) noise and amplitude-modulation industry. Allan deviation another based on the use of a 1 GHz repetition- The and (AM) noise of clocks and oscillators rate, mode-locked laser and the applica- statistic, total deviation, both require data presumes the availability of stable refer- tion of a scheme that requires coverage of acquisition over twice the period of the ence oscillators at the desired measure- only of an octave. In this self-referencing desired averaging interval. For example, to ment frequencies. However, it is too scheme, the 2"'' and 3'''' harmonics of the determine the stability at 1 month would expensive and cumbersome to maintain optical signal of interest are heterodyned require a two-month-long data run. dedicated reference oscillators for each with elements of the frequency comb to Recently, we developed a new statistic measurement frequency To date, methods ultimately lock the 1 GHz repetition rate that yields a measure of stability at the for synthesizing offsets from stable, fixed- of the mode-locked laser to the optical end-point of the data sehes. The most frequency oscillators have been extremely signal. While our new 1 GHz femtosecond significant effect of this advance is to cut complex. The problem is that frequency- laser just generates a full octave, further required measurement times in half, thus offset synthesis generally creates development will be needed to allow substantially cutting the cost of acquiring unacceptable levels of noise. reliable locking using only the fundamental the most expensive data point. and 2"'' harmonic of the optical signal. We recently developed a simple reference-

Moreover, the statistic not only retains oscillator system with broad tunability The immediate consequence of this devel- all of the desirable features of the Allan but without much of a noise penalty In opment is to increase the uninterrupted, deviation, it has fewer intrinsic biases and the traditional approach, a synthesized microwave-frequency output, self-referenced much narrower confidence limits. We offset is added to a stabilized oscillator to an optical transition, from tens of minutes found that a more complex combination Therefore, the noises of these two signal to about a day Such improvement in of frequency sums and differences could are independent and additive. reliability is essential to the future of optical- yield an Allan-like statistic clear out to frequency standards, since, ultimately the interval of the data run itself. such standards will have to operate

unattended for long periods. In the

41 The innovation of the new system is in Chip-Scale Atomic Clock systems, particularly GPS, and civilian the placement of the offset synthesizer technology such as wireless telephony. Earlier fundamental research at NI5T on inside a servo control loop used to stabi- a very small atomic clock, based on the We are focusing on several projects. lize a high-Q microwave cavity. The fre- concept of coherent population trapping, The first involves characterizing miniature quencies of two oscillators, the reference has served to focus broader interest on vapor cells, both wall-coated and buffer- signal and the offset, must add up to the the subject of miniaturization. In fact, a gas-filled cells. One of the objectives will fixed resonance frequency of the cavity new DARPA-funded program was stimu- be to experimentally establish the scaling Therefore, the reference-signal frequency lated by a NIST-hosted workshop held 1 'A (size) laws, thus defining the limits for will be changed in a direction opposite to years ago in Boulder. The advantage of miniaturization. We are also supporting changes in the synthesized offset frequency. the coherent-population-trapping concept studies at the University of Colorado The system suppresses the total noise on is that the traditional microwave cavity is of the cell-wall coatings deemed to be the reference signal. eliminated. The need for a microwave cavity essential to miniaturization to the sub-

has long been an impediment to miniatur- millimeter level. An auxiliary study, being

ization below the few-centimeter level. performed collaboratively with NIST EEEL

staff, is to examine the potential of direct We are now collaborating with a group interaction between magnetically coated of eight companies and universities, also MEMS oscillators and atoms. Success in funded by DARPA, on developing a chip- this experiment could provide a dramati- scale atomic clock. Because of our expertise cally simpler approach to miniaturizing in miniaturizing atomic clocks, we will atomic clocks and atomic magnetometers. study basic aspects of miniature atomic

clocks to help guide developments on CONTACT: Dr. John Kitching this aspect of the program. Success in this (303) 497-4083 endeavor could have impact on military [email protected]

fourth strategic focus is to develop quantum- Figure 6. David Howe and Craig Nelson with The the microwave cavity used to suppress noise logic components and quantum-information systems in their new reference oscillator based on trapped ions, in support of new atomic frequency

standards and a national program aimed at advancing The concept was experimentally demon- strated using a high-Q microwave cavity computation and communication. with a resonance frequency of 10.6 GHz, a dielectric resonant oscillator, and a Quantum-Information as the basis for quantum computation, digital offset-frequency synthesizer. The quantum measurement, and noise results demonstrated the addition of Processing Using reduction in atomic clocks. tunability without substantially adding to Trapped Ions the noise. This development advances the The current program grew out of a NIST art of PM and AM noise measurement. INTENDED OUTCOME AND competence project to reduce fundamental, BACKGROUND quantum-projection noise in multi-ion CONTACT: Dr. David Howe atomic clocks. The realization that the 497-3277 The intended outcome of this program (303) same trapped-ion systems could also be [email protected] is the development and demonstration used for quantum information processing of prototype logic circuits that can serve

42 generated substantial outside interest. As ACCOMPLISHMENTS scaling to larger logic systems. For example, a result, the ion progrann expanded and there is no requirement for maintaining

its success stimulated the development Geometrical-Phase equal laser couplings to each ion as in the of other quantum-computation and Quantum-Logic Gate previous, two-qubit gate. This means that quantum-communication programs at sympathetic cooling can be used in more The recent demonstration of a novel, NISI Today, the ion quantum-information complex systems without introducing two-qubit, geometrical-phase quantum- project represents only a portion of a NIST difficulties in maintaining specific laser- logic gate significantly advances prospects centrally coordinated effort that now has beam couplings to the ions. In addition, in for quantum computation. This new gate fairly broad objectives. contrast with the practical realization of appears to have features that overcome other gates, the phases imposed on qubits a number of difficulties identified earlier. There are several strong motivations for can be generated with co-propagating this work. From a national perspective, In this device, rather than manipulating Raman laser beams. This means that the developing a quantum computer, while an the direction of the spin states, we control qubit phases will be highly immune from extremely challenging undertaking, would the phases of the spin states using optical displacement between the ions and the have a major impact. This arises from the dipole forces. The greatest advantage of laser beams. Thus, motions (vibrations) of fact that a quantum computer should be this change is that the requirements on the trap relative to the laser beams will able to perform certain functions expo- control of the phase of the probe laser are cause fewer problems. nentially faster than even the largest array dramatically reduced. For gates of the sort of conventional computers. As examples, we demonstrated and reported two years CONTACT: Dr. David Wineland a quantum computer could much more ago in Nature, the laser phase had to be (303) 497-5286 efficiently factor large numbers, a process [email protected] kept constant throughout the full, coher- that is at the heart of decryption, and it ent sequence of operations on the entire could greatly speed database searches. set of qubits involved in the system. For

the new gate, the laser phase has to be The second broad motivation is the well controlled only during a single-gate expected impact on measurement science.

operation. This is dramatically easier to do. The ability to produce and manipulate arbitrary states of single atoms and The geometrical-phase gate also shares collections of atoms has clear implications many of the positive attributes of the for measurement science and for atomic earlier gate. It is a one-step gate. All of clocks in particular. Last year, we demon- the qubits involved can be placed into strated noise reduction below the standard proper states at the same time. Also, quantum limit for two entangled ions, individual-ion addressing is not required. and implied that these methods can be In fact, the ions are best illuminated simul- extended to many ions, providing for taneously This means that careful laser

increased performance in atomic clocks. is not needed. Finally, motional focusing Figure 7. David Wineland adjusting one of the More generally, the ability to engineer eigenstates are not required as long as the systems used for studying quantum-logic gates. quantum states at the single- and few- ions are tightly contained and within the atom level has implications for metrology Lamb-Dicke limit. in nanoscale systems.

The new gate is particularly well suited

to application in multiplexed trap systems,

a design approach that will provide for

43 GOAL: TO PROVIDE FUNDA-

MENTAL UNDERSTANDINGS OF.

NANO-, BIO-, AND QUANTUM

OPTICAL SYSTEMS IN PARTNER-

SHIP 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 ACCOMPLISHMENTS laser as a precise measurement tool. Precision Spectroscopy of Cold Atoms and Molecules Laser Research been exploited to guide atoms through We have extended the coverage of hollow fibers and prevent them from iodine-based, optical-frequency standards

INTENDED OUTCOME AND touching the sides. The Division has a toward the shorter wavelength region,

BACKGROUND rapidly developing research program in from 532 nm to 500 nm. Owing to the

attractive properties Laser capabilities today are used for a ultrafast phase-control and frequency of newly discovered resonances, linewidth wide variety of industrial and scientific measurements, which are applied to namely narrow and purposes, ranging from providing the control atomic and molecular dynamics, high signal-to-noise ratio, we are develop- length scale for mechanical measurements as well as to access wholly new types ing a new generation of cell-based optical-

frequency instability less to providing a means to directly connect of frequency and length standards. standards with the optical- and microwave-frequency than 10 f Hz/Hz at 1 s averaging time. We One of our senior scientists, Jan Hall domains. The Quantum Physics Division have made absolute frequency measure- (one of JILA's original scientists), is widely ments on several of these transitions continues a leadership role in these fields, acknowledged to be the "father" of using the JILA-developed, developing new techniques vis-a-vis femtosecond, much of the laser stabilization and associ- have also precision lasers and their applications. frequency-comb technology We ated precision-measurement methods that discovered new and interesting changes in are NIST, international In laser research, various are used today by the schemes the hyperfine interactions of the iodine explored for stabilizing lasers for using standards community, and leading univer- and molecules when the transitions approach them as frequency standards. Recent work sities throughout the world. Our recent the dissociation limit in the excited state. of the Division addresses the creation, hires serve to further strengthen this

activity a Broadband, femtosecond lasers and ultra- utilization, and study of ultrafast laser pulses, and to assure NIST of continuing high-resolution spectroscopy have been which can be applied both to produce world-leadership position in this critical

linked in experiments laser-cooled and control wave packets and to study standards and measurement domain. on rubidium (Rb) atoms. phase-coherent, nonlinear optical-wave interactions. The A wide-bandwidth optical comb was used evanescent-wave property of light has to induce multi-path quantum interfer-

ence for the resonantly enhanced, two-

44 photon transition in cold Rb atoms. We OH cold collisions with a controlled ond-level precision. We have already

have also dennonstrated the possibility of magnetic field. We believe these kinds demonstrated all-electronic, precision

using cold atonns to control both degrees of experiments will mark a new era in switching between two time delays, with of freedom for the femtosecond-laser physical chemistry. high speed and no hysteresis. In principle, system, namely the comb spacing and our active-synchronization technique could the carrier-offset frequency. CONTACT: Dr. Jun Ye lock together as many different lasers (303) 735-3171 with different gain media as desired. Working with the trap dynamics of laser- [email protected] cooled, alkaline earth, ^^Sr atoms, we (2) Nonlinear imaging for biological

have established the first rigorous test of applications. We have reported another Precision Frequency Doppler-cooling theory in a strictly two- significant breakthrough in ultrafast tech-

level atomic system. We have also, for Metrology and Ultrafast nology that has potentially a wide range the first time, magnetically trapped the Science of applications. We apply our synchroniza-

*^Sr atoms in their long-lived, metastable tion technique to coherent anti-Stokes By achieving the first experimental states, paving the way for a possible evap- Raman scattering (CARS) spectroscopy, demonstration of tight synchronization orative-cooling route toward quantum one of the most powerful methods for and controlled phase coherence between degeneracy of the alkaline-earth atoms. acquiring chemically-selective maps of independent femtosecond (fs) lasers, we Furthermore, we demonstrated the exis- biological samples. With the availability have opened up a new sub-field in ultra- tence of a sub-Doppler cooling mecha- of tight synchronization, we can now utilize fast science. The following is a list of nism for the fermionic isotope ^^Sr using two independent picosecond (ps) lasers, novel experiments performed in the its nuclear magnetic substructure. ^'Sr has with great flexibility of wavelength tuning laboratory in the past year. been identified as the best candidate for and pump-power manipulation. We have an ultimate optical-frequency standard (1) Sub-femtosecond ultrafast laser shown that technical noise associated based on cold neutral atoms, due to the synchronization. The ultimate goal of with timing jitter can be completely elimi- existence of an electromagnetic-field- this research is to develop an arbitrary nated from the CARS signal, and we have insensitive, narrow, forbidden transition lightwave generator. To do this, one must recorded CARS vibrational images of living

have a timing jitter the optical- from 'So to 'Pq. below cells and polymer beads with significantly

carrier period. For 800 nm, this is 2.7 fs. improved quality. This new technical capa- Our cold molecule "machine" has started We implemented a wide-bandwidth servo bility will be of great interest to chemists, to produce results. The goal of this project loop to synchronize two independent materials scientists, and biophysicists. is to explore control techniques on mole- mode-locked lasers on a sub-femtosecond cules similar to those applied to atoms. (3) Arbitrary wavelength/spectrum time scale, with 1 ms averaging. Even We have successfully produced rotation- generation. We have demonstrated a with a detection bandwidth above 2 MHz, and vibration-cooled OH radicals from a new experimental approach for flexible we still see a timing jitter of under 2 fs. pulsed, supersonic beam source. These femtosecond pulse generation in the mid- This is the lowest timing jitter ever reported polar molecules can then be guided IR, using difference-frequency-generation using an active-synchronization scheme, downstream using high-voltage, electro- from independent Ti:sapphire (Ti:S) lasers. and even passive techniques have not static fields that can be switched to slow This work represents a significant step been shown to be any better. down the translation velocity. We will towards realizing an ideal light source for of using active eventually trap the cold molecules in an There are many benefits coherent control of molecular vibrations

(as passive). electrostatic trap and perform the first synchronization opposed to in the mid-IR region. For example, we can arbitrarily set the

time delay between the two pulse trains

to any value we choose, with femtosec-

45 —

The resultant mid-IR pulse train can be fHz/Hz at 1 s is transferred from NIST to Progress In Cell-Based easily tuned, with an adjustable repetition JILA via this link. This maser-based rf refer- Optical-Frequency Standards frequency up to 100 MHz. Arbitrary, ence, about ten times more stable than With the recent breakthrough in optical- rapid switching of the generated wave- our commercial, cesium atomic clock, is frequency measurements using fs-laser length and progrannnnable amplitude used as the time base for femtosecond-

comb technology, it is clear that optically modulation are achieved via precision laser-based optical combs used for based frequency standards will play a setting of the time delay between two absolute optical-frequency measurements. decisive role in future frequency standards ohginal pulses. The average power of The maser-based signal is also used to and applications. Right now, the NIST the pulses exceeds 1 5 pW, which to our make direct comparisons against the out- program in ion-trap systems is the world knowledge represents the highest power put of an optical clock, i.e., the repetition leader. However, gas-cell approaches in the > 7.5 (jm spectral range obtained frequency of the femtosecond comb stabi- appear capable of providing comparable from direct difference-frequency-generation lized by an optical transition. This optical- stability at vastly less cost and in more of Ti:S pulses. frequency standard is based on an iodine- compact space, although with somewhat stabilized Nd:YAG laser at 1 064 nm with (4) Optical frequency metrology. less accuracy potential. an instability of = 40 fHz/Hz at 1 s, which Having demonstrated last year the first is transferred from JILA to NIST using the Accordingly, we have developed a full optical atomic clock, we have now second fiber. With independent femtosec- theory of the limits achievable with com- improved its simplicity and reliability The ond frequency combs operating in both pact, gas-cell-based, optical-frequency optical atomic clock offers unprecedented laboratories, the absolute optical frequency standards. This shows that another factor- short-term stability and will provide better can be measured simultaneously with of-ten improvement should be possible long-term stability as well. We note that reference to the common maser-based on our iodine-based system, which has our progress has been acknowledged with rf standard. already been shown to be more stable a large MURI contract from the Office of than other available frequency sources Naval Research, with JILA as the center A direct optical-frequency comparison including the NIST H-maser—for times less of this multi-university research project. enabled by the fiber link was also carried than a few hundred seconds. Use of a still out, with results that are clearly superior Comparison and dissemination of the more favorable transition should provide to the rf-based measurements. We meas- optical-frequency standards and atomic- another five-fold gain. Another major ured the degradation of the optical and clock signals have now become an urgent advance likely to improve the long-term rf standards due to the instability in the need. We have carried out work in trans- stability is in the technology of distortion- transmission channel and developed mitting and comparing highly stable rf- free modulation, where we recently methods for active frequency-noise can- and optical-frequency standards using two demonstrated that fringing fields in the cellation over the 6.9 km roundtrip dis- dark fibers already installed in the Boulder Electro-Optic Modulator (EOM) could tance. Optical-frequency transfer instability Research and Administrative Network be controlled. between JILA and NIST through the BRAN (BRAN). The optical link between our labs fiber is now about 3 fHz/Hz at 1 s after Dr. L. Hall at JILA and NIST Boulder is 6.9 km long, CONTACT: John noise cancellation. A unique aspect of the (303) 492-3126 roundtrip. A hydrogen-maser-based rf optical phase-noise compensation is that [email protected] standard with an instability of = 240 the transit time of the optical link

is comparable to the coherence time

of the laser, leading to interesting coher-

ence effects.

CONTACT: Dr. Jun Ye (303) 735-3171 [email protected]

46 Phase Control of Ultrashort Spin Coherence in A/-Doped Complete Measurement Optical Pulses Semiconductors. of Exciton Scattering

During the last few years, there has been The possibility of using the spin degree- in Quantum Wells a remarkable convergence between the of-freedom of electrons for encoding Many-body interactions among carriers technology of ultrafast lasers and that information has recently attracted signifi- influence the performance of optoelec- used to stabilize single-frequency cw cant attention. Proposed implementations tronic devices, such as laser diodes and lasers. This has led to significant advances include devices analogous to traditional semiconductor optical amplifiers. Ultrafast in the fields of optical-frequency metrology microelectronic devices and those based measurements of coherent processes in and optical atomic clocks. It also promises on quantum-information concepts. semiconductors, using techniques such as to have a large impact on ultrafast science Optical techniques are currently the best transient four-wave-mixing (TFWM), have by making it possible to control the carri- way to prepare and probe spin-coherent proven to be very sensitive to many-body er-envelope phase of ultrashort pulses. states, as true "spintronic" devices are still interactions. The results of these measure-

very primitive. In addition, optical prepara- ments test the fundamental theories used Control of the carrier-envelope phase tion and probing is likely to be useful to model devices. will allow arbitrary electronic waveforms for quantum-information applications. (as opposed to intensity waveforms) to be We are using a 3-pulse implementation synthesized at optical frequencies. Such The observation at the University of of TFWM to study excitonic scattering electronic-waveform synthesis will be California (Santa Barbara) of very long processes in GaAs/AIGaAs multiple quan- useful in signal-processing applications, spin-coherence times in n-doped, bulk tum wells. By using a 3-pulse configura- in coherent control of quantum processes, GaAs provided significant impetus for our tion, we can measure decay of the and in extremely nonlinear optics. research. We use the technique of Faraday Raman-like coherence between the heavy-

rotation to probe the spin coherence of hole and light-hole excitons. In the same Before these avenues can be explored, to it such systems and study how depends experiment, it is also possible to observe a train of optical pulses with identical on the density of optically excited elec- coherences between the heavy-hole exci- carrier-envelope phase must be generated, trons, which are initially spin polarized. ton and the ground state, and between i.e., the carrier-envelope phase coherence the light-hole exciton and the ground must be preserved for times longer than We have shown that the spin-coherence state. By studying these simultaneously, it takes to perform an experiment. The time decreases at high excitation density insight is gained into how coherence is carrier-envelope phase evolution in the and that the electron g-factor changes sub- lost during scattering events. The relative pulse train emitted by a mode-locked tly The decreased spin-coherence time is dependence of the scattering rates on the laser is manifest as an offset frequency, /o, attributed to an increase in spin-spin scat- excitation density and sample temperature in its spectral comb, with carrier-envelope tering amongst the electrons. The variation helps distinguish carrier-carrier scattering phase fluctuations causing the spectrum of in the g-factor is presumably due to its and phonon-carrier scattering. /o to broaden. /c-dependence, coupled with the change

in the average k of the electrons as the Recent results show that, with optimiza- CONTACT: Dr. Steven Cundiff excitation density is changed. This is being (303) 492-7858 tion of the stabilization, the linewidth of tested by examining several samples with [email protected] /o can be below 1 MHz, corresponding to different doping densities. Measurement a carrier-envelope phase coherence time of the /c-dependence of the g-factor is of hundreds of seconds. important since it effectively broadens the

electron-spin precession, thereby decreas- CONTACT: Dr. Steven Cundiff ing the observed spin-coherence time. (303) 492-7858 [email protected] CONTACT: Dr. Steven Cundiff (303) 492-7858 [email protected]

47 —

The second strategic element is to exploit Bose- BEC on a Chip Einstein condensation and quantum-degenerate Fermi In other cold-boson work, we have

succeeded in injecting a condensate into a gases for metrology and ultralow-temperature physics. lithographically patterned microstructure,

an "atom chip." The long-term techno-

logical goal of this work is to develop Bose-Einstein and Additionally, a program to use current- super-precise inertia! sensors, i.e., gyro- carrying wires as "pipes" to both guide Fermi-Dirac Gases scopes and gravity gradiometers. The and "split" cold atoms for atom interfer- condensate will travel through the chip and INTENDED OUTCOME AND ometry is being aggressively pursued. be coherently split and recombined. The BACKGROUND resulting interference signal will be exquis-

The Quantum Physics Division and JILA itely sensitive to minute inertial effects. are today a world focal point for studies ACCOMPLISHMENTS For now, our very preliminary condensate- of Bose-Einstein condensates and quan- in-chip studies have demonstrated that tum-degenerate Fermi gases. The mutual Frequency Shift Metrology minute imperfections in the wire can have advantage to NIST and the University of We are in the midst of a series of studies deletehous effects on the condensate's Colorado in collaborating at JILA was to understand the microwave transition in coherence. Our new generation chips best exemplified when Eric Cornell (NIST) ultracold rubidium. Ultracold temperatures will be constructed with considerably and Carl Wieman (CU) together achieved and magnetic-trapping technology make more attention to this issue. for the first time a Bose-Einstein conden- possible interrogation times extending to sate, and for that accomplishment were 2 s, which leads to very narrow line widths CONTACT: Dr Eric Cornell awarded the 2001 Nobel Prize in Physics. and correspondingly higher precision. (303) 492-6281 Coupled with the creation of the first [email protected] Residual interactions between the atoms quantum-degenerate Fermi gas by cause shifts in the transition frequency Deborah Jin (NIST) and one of her CU that must be accounted for. We can track graduate students, Brian DeMarco, this these small shifts with great accuracy places the Quantum Physics Division and since the extended interrogation time JILA at the forefront of studies of macro-

makes it possible to follow the frequency scopic—and therefore easily studied shifts as the cloud heats, cools, decoheres, quantum-mechanical systems. and even undergoes a phase transition

A better understanding of these systems into or out of a Bose-condensed state. is critical today because the miniaturiza- Many of the observed effects are quite tion of electronic components is pushing countehntuitive, and therefore help us into the size region where quantum-

reshape our understanding of what it mechanical effects play a significant role

means for a sample of gas to lose its in their operation. We plan to continue internal coherence. Figure 1. Eric Cornell, co-discoverer to explore and exploit the new quantum- (together with Carl Wieman) of Bose-Einstein mechanical systems that these discovehes CONTACT: Dr Eric Cornell condensation in dilute atomic vapors. have made accessible, and maintain our (303) 492-6281 leadership position. [email protected]

48 "Destroying" BEC Cold Fermions

Ironically, one of the more important sci- We successfully implemented a number of entific advances in our ultracold research new experimental capabilities that this year is progress not towards creating enhance our research opportunities in a Bose-Einstein condensate but towards exploring Fermi gases of cold atoms. We destroying it. As a ball of Bose-condensed developed a far-off-resonance, optical- gas starts to rotate, it becomes pierced by dipole trap for confining fermionic atoms progressively more, tiny tornadoes known in any combination of hyperfine spin- as quantized vortices. When the rotation states. This trap will be used to search rate is very high, these vortices organize for a new superfluid phase driven by themselves into a tightly packed, triangular resonant interactions in the gas. array. At the highest level of rotation, the To this end, we made the first measure- size of each vortex becomes large com- ment of a magnetic-field-tunable, pared to the spacing between the vortices. Feshbach scattering resonance for fermi- Figure 2. Deborah Jin aligns an infrared laser

trap is Theory predicts there will be a reordering onic atoms. This resonance allows us to for a magneto-optical trap. The used

to collect 1 billion rubidium atoms under ultra- transition in which the condensate is control interaction strengths and is a key high vacuum. The atoms are then sent to a destroyed, to be replaced by a highly ingredient for realizing resonance super- second trap under even higher vacuum and correlated gas reminiscent of the quantum fluidity as predicted by Holland and co- cooled to 100 nanokelvin. The result is a so Hall state in solids. Achieving and charac- workers. We have also measured the first called "Bose Einstein condensate" in which

in lab is for terizing this transition the a prime p-wave Feshbach resonance fermionic a large number of atoms behave coherently. scientific goal, because we anticipate it atoms. This resonance occurs in the scat- will generate important insights into tering of atoms in the same spin-state and analogous transitions in technologically could provide a mechanism for realizing important, condensed-matter systems, superfluidity with p-wave Cooper pairs. including the giant-magneto-resistance In another experiment, we demonstrated phenomenon that is so vital to progress in simultaneous cooling and trapping of disk-drive read-sensor technology. During Bose and Fermi gases in the quantum the year we advanced the figure-of-merit regime. Bose-Einstein condensates for producing the transition a factor of are produced using ^''Rb atoms. Simul- 20 closer to the goal. taneously trapped, fermionic *°K atoms

are cooled sympathetically and reach CONTACT: Dr. Eric Cornell (303) 492-6281 roughly a quarter of the Fermi tempera- [email protected] ture. Work is proceeding in characterizing

this new system.

CONTACT: Dr. Deborah Jin (303) 492-0256 jin@jilau1 .colorado.edu

49 —

The third strategic element is to investigate biologi- The operation of this apparatus is as follows. A pulse train from a mode-locked cal systems at the single-molecule level. With a new laser (532 nm, doubled Nd:YAG, 80 MHz thrust in biophysics, the Quantum Physics Division aims repetition rate) is focused into an aqueous

sample with a water-immersion micro- to investigate critically important biological systems at scope objective (NA = 1.3), thereby the single-molecule level, drawing upon our measurement illuminating = 0.1 femtoliter of solution. expertise and experience with atomic and quantum systems. For sufficiently dilute samples of labeled DNA/RNA, this corresponds to less than

single-molecule occupancy in the detec-

tion region, which permits laser-induced Biophysics Cellular, and Developmental Biology, and fluorescence from single molecules to with the Biochemistry Division of the be unambiguously monitored. INTENDED OUTCOME AND Chemistry Department. BACKGROUND The resulting weak fluorescence is colli- We expect that bridging JILA to additional As JILA and the Quantum Physics Division mated, separated from the = 10^ fold departments will enhance the very pro- lool< to the future, it is clear that an stronger, incident laser with high-rejection ductive, interdisciplinary character of JILA. important scientific revolution is presently dichroic filters, sorted by both polarization Most importantly, we expect to be able to taking place in the area of biophysics. and color, and finally imaged on single- find a niche where, by capitalizing on our Accordingly, we are evolving a part of our photon-counting avalanche photodiodes. existing expertise, we will be able to bring research program in this direction to help The individual photon events are then this program to the same very high stature NIST contribute to and be a meaningful efficiently sorted by color and polarization as we have for our other programs. part of this scientific future. and stored as a function of time-after

This year, three research projects were the incident laser pulse. The fluorescence Our strengths—namely, our ability to build initiated, with NIST and other-agency sup- dynamics of the biopolymers are then institutional bridges to university depart- port. They build on our fundamental laser extracted via time-correlated, single- ments that are already strong in this area, skills and chemical-physics experience, and photon counting. This permits measure- a superlative infrastructure that serves to contribute as well to the rapidly evolving ment of fluorescence decay rates of the extend the quickness of our eyes and the NIST research programs in nanotechnology labeled DNA/RNA species, or fluorescence- reach of our hands, our experience in and single-molecule biophysics. resonant-energy-transfer (FRET), between manipulating and measuring similarly donor and acceptor dyes on a single sized atomic and quantum-mechanical DNA strand. systems, and a reputation that allows us to attract and successfully hire the best ACCOMPLISHMENTS In a complementary thrust, we are devel- and brightest of today's young scientists oping methods for immobilizing dye- Fluorescence Microscopy all suggest that we can hope to become labeled biomolecules in aqueous gels to a significant contributor to this scientific Studies of Biomolecular allow us to measure fluorescence and to revolution. We have therefore embarked Conformational Dynamics image single molecules by raster-scanning on a program in biophysics that is to be of the laser over the sample with a preci- This biometrology project is based on carried out in close collaboration with sion, PZT, servo-controlled stage. ultrasensitive time-, color-, and polariza- the University of Colorado, in particular tion-resolved fluorescence detection of with the Department of Molecular, single biomolecules (specifically, dye-

labeled DNA and RNA oligomers) in a high-

numerical-aperture confocal microscope.

50 The combination of FRET, immobilized high biomolecular strand lengths. Also of trapped bead attached to the DNA's distal

labeled biomolecules, and ultrasensitive interest are kinetics/dynamics of protein- end. To date, unitary steps of DNA-based

single-molecule detection methods DNA/RNA binding, which are relevant to molecular motors have been too small

offers new opportunities for directly cell regulatory processes and would now to resolve. Their presumed step sizes are

probing the extremely important confor- be amenable to detection at the single- 1 .4 nm or smaller, but such steps may be

mational dynamics of biomolecules in molecule level. attenuated by the compliance of DNA.

real time, e.g., folding and unfolding. Building on our demonstration that 0.3 nm Dr. David J. Nesbitt This class of information is of crucial CONTACT: (303) 492-8857 steps of a stuck bead can be resolved, we relevance to issues concerning RNA- [email protected] are building a microscope for measuring based enzymes, so-called ribozymes. 1 nm motion along DNA. The electronics

for this microscope are a high bandwidth CONTACT: Dr. David Nesbitt Single-Molecule (303) 492-8857 (250 kHz) quadrant photodetector con-

[email protected] Measurement with nected to a differential normalizing ampli-

Nanometer Resolution fier. These detectors do not exhibit wave-

length-dependent reduction in bandwidth The biochemical cycle of mechano-enzymes Single-Biomolecule as seen in earlier designs. By incorporating generates a force and a displacement that Electrophoresis PZT mirrors instead of acousto-optic deflec- can be measured at the single-molecule tors, we eliminate the nanometer-sized, A second new biometrology project is level. The third new project aims to deter- artifactual steps obsen/ed to arise from single-molecule electrophoresis. The mine how motor proteins transduce standing waves inside the AO crystal. apparatus for these studies is based on chemical energy into physical motion. wide-field microscopy through a thin

This research focuses on developing assays CONTACT: Dr. Thomas T. Perkins gel-electrophoresis cell, in which weak and precision instrumentation to measure (303) 492-8186 electric fields (1 V/cm to 5 V/cm) are [email protected] the properties of single DNA-based molec- used to coax single DNA molecules

ular motors. The enabling technology is through a = 20 |jm x 20 pm field of view. optical tweezers, a focused laser beam The DNA molecular motion can be stud- that can manipulate micrometer-sized ied by labeling with highly fluorescent

beads in solution, allowing measurements dyes that are illuminated with cw 488 nm of position and force in the nanometer laser excitation and detected by imaging and piconewton ranges. on an intensified, CCD camera. The

sensitivity of the method is sufficient to Measurement of steps and stall forces image at a 10 Hz frame-repetition rate. provide fundamental information on the This permits monitoring of single DNA mechanics of motion. For many enzymes,

electrophoretic dynamics in real time. different proposed mechanisms of motion

predict different step sizes. Steps have These sorts of studies permit detailed tests been seen for myosin along actin (5.5 nm) of "reptation" models of electrophoresis Figure 3. Using a modified microscope, and for kinesin along microtubules (8 nm). Tom Perkins measures the motion and can begin to address issues in improv- generated by a single enzyme moving along DNA. ing separation efficiency in the limit of Enzymatic motion along the DNA is meas-

ured by anchoring the enzyme to a surface

and monitoring the position of an optically

51 GOAL: TO COORDINATE

AND FACILITATE THE

ELECTRONIC DISSEMINA-

TION 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 interest, and news items. In a recent ACCOMPLISHMENTS month (October 2002), there were nearly

of Information one million requests for web pages from Units Markup Language

Gaithersburg server (nearly half from INTENDED OUTCOME AND the We have continued a collaboration with BACKGROUND our =25 online databases), and nearly Lawrence Berkeley National Laboratory 8.8 million requests for web pages from and NIST's Electronics and Electrical The Office of Electronic Commerce in all PL web servers (including time.gov Engineering Laboratory to develop an Scientific and Engineering Data (ECSED) and tf.nist.gov). XML (extensible Markup Language) is responsible for the Physics Laboratory schema for encoding scientific measure- (PL) world wide web (WWW) pages at There are many new web databases ment units. Adoption of this schema will physics.nist.gov. We produce material currently under development, including: allow for the unambiguous exchange of for WWW publication, encourage and 1) Handbook of Basic Atomic numerical data over the Internet. support the production of material Spectroscopic Data, by others, and ensure the high quality We are in the process of creating an

of disseminated information. are international to examine We 2) Spectral Data for the Chandra working group

also engaged with PL Divisions and the X-ray Observatory, and discuss the completed first draft of

NIST standard Reference Data Program in the UnitsML schema. In addition, we have

developing physical reference databases 3) X-ray Transition Energies Database, begun collaborating with the NIST Infor-

for WWW dissemination. We design mation Technology Laboratory to establish 4) Chemical Agents Database, and develop effective WWW database a NIST registry containing SI and non-SI

interfaces to facilitate access to the data. unit information and to create an 5) Potentials of Alkaline-Earth Dimers, XML

registry containing the UnitsML schema. Since June 1994, we have provided a 6) Amorphous Metals Database, and We anticipate this registry will be used wide array of information ranging from by our customers to download industry- physical reference data, technical activi- 7) Hydrogen and Deuterium Energies specific dictionaries of scientific units. ties, research and calibration facilities, and Transition Frequencies

technical contacts, publication lists, general (an interactive website). CONTACT: Dr Robert Dragoset (301) 975-3718 robert, [email protected]

52 Molecular Spectroscopy of chemists and physicists for conventions quantum numbers, observed frequency,

and guidance in working with the complex estimated measurement uncertainty, Tutorials On-Line and mathematics involved in calculating the reference are given for each transition. We collaborated with the Optical rotational energies and intensities of The spectral lines for many molecules and Technology Division to make available on tetrahedral molecules, such as methane normal isotopic species have been refit to the WWW two popular tutorials in nnolec- and carbon tetrachloride. Scientists inter- produce a comprehensive and consistent ular spectroscopy. The original documents ested in atmospheric sensing, combustion analysis of all the data obtained from were converted to HTML, and the equa- diagnostics, and climate change will benefit many sources. The derived molecular tions were formatted as both images and from ready access to this document. properties, such as rotational and centrifu- LaTeX to ensure their wide accessibility. gal distortion constants, hyperfine struc-

CONTACT: Mrs. Gloria Wiersma ture constants, electric dipole moments, The first of these documents is the exten- (301) 975-5547 rotational g-factors, and internuclear sively cited NBS Monograph 1 1 5, The [email protected] Calculation of Rotational Energy Levels distances (for diatomic molecules) are and Rotational Line Intensities in Diatomic listed with one-standard-deviation

uncertainties for all species. Molecules, h ttp://physics. n ist. gov/ Molecular Databases On-Line

DiatomicCalculations. It played a major We collaborated with the Optical The Diatomic, Triatomic, and Hydrocarbon role in standardizing the complex conven- Technology Division to make available on Spectral Databases can be accessed on tions and nomenclature used to describe the WWW three linked databases of the the WWW at http://physics.nist.gov/ the quantum-mechanical behavior of microwave and RF spectra of diatomic, MWtables. Further information on diatomic molecules. triatomic, and hydrocarbon molecules. additional molecular spectroscopic data-

The document describes the derivation Originally published as spectral tables bases developed by the Office of ECSED of the intensities of the spectral lines, and in the Journal of Physical and Chemical is available at http://physics.nist.gov/data. contains a clear discussion of the rotation- Reference Data, the on-line version Development of these databases was includes additional molecules allows al Hamiltonian and its symmetry proper- and supported in part by NiST's Standard ties, necessary for calculating molecular advanced browsing and searching of Reference Data (SRD) Group and by NIST's energy levels. This pedagogical mono- the data—by molecular species, type, Systems Integration for Manufacturing or frequency graph is of interest to the wide communi- Applications (SIMA) program. ty of scientists dependent on molecular Rotational spectral lines for 121 diatomic spectroscopy for their success, including molecules, 55 triatomic molecules, and CONTACT: Mrs. Karen Olsen atmospheric and planetary scientists, (301) 975-3286 91 hydrocarbon molecules are included. astronomers, plasma physicists, and [email protected] The isotopic molecular species, assigned analytical chemists. It is the accepted, more rigorous companion to the popular

Figure 1 . Screen capture of a brow/ser Viow Go Scuikmafkfl Toob v^^Oon Hatp hllp^A)hyBicajiittgo'ivMWatiieri ^ I ^ textbook, Spectra of Diatomic Molecules, window for the "Molecular Spectral Physical Reference Data written by the late Nobel Laureate Databases" main web page. Molecular Gerhard Herzberg. Spectral iCTOwc^vesDatabases The second tutorial newly offered on- Si^tomic Spectral Database line is Methane Symmetry Operations, Diatomic Spectral Database http://physics.nist.gov/Methane. It was Hydrocarbon Spectral Database initially written in response to the needs

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

The Bose-Einstein condensate, first demonstrated scientists. In 1997, William D. Phillips received the Nobel Prize for pioneering research by NIST and University of Colorado scientists on cooling and trapping atoms with laser light. The Bose-Einstein condensate, or BEC, is at JILA, was Science magazine's 1995 Molecule essentially a new form of matter that allows scientists to study the strange and extremely of the Year. A new state of matter, the BEC

"superatom," forms as rubidium atoms trapped small world of quantum physics. Its creation in 1995 by Cornell and Wieman established in a magnetic field are cooled to a temperature a new branch of atomic physics that has provided a treasure-trove of scientific discoveries, close to absolute zero. The graphic shows including the atom laser, first demonstrated by Ketterle, quantum whirlpools, atom wave- three-dimensional, successive snapshots in guides, and other coherent atom-optical phenomena. time during which the atoms are cooled to

less than 170 billionths of a degree.

54 Max Born William 0. Baker Maria Award Award Goeppert-Mayer Award

John L. Hall Deborah S. Jin, Deborah S. Jin was also awarded the

Quantum Physics Quantum Physics Maria Goeppert-Mayer Award of the

Division, was pre- Division, was award- American Physical Society, "for her inno-

sented the Optical ed the National vative realization and exploration of a

Society of America's Academy of Science novel quantum system, the degenerate

Max Born Award Award for Initiatives Fermi atomic gas, and the scientific

"for pioneenng the in Research, "for her promise portended by her pioneering field of stable lasers, including their appli- experimental realization and characteriza- work." This award recognizes the wide-

cations in fundamental physics and, most tion of a new quantum system, the vapor- ranging future implications of work in

recently, in the stabilization of femtosec- phase degenerate Fermi gas." Known as ultra-cold gases.

ond lasers to provide dramatic advances in "the Baker Prize," the award recognizes

optical frequency metrology." Jan is one innovative young scientists for research

of the "fathers" of today's laser-generated likely to lead towards new capabilities

optical combs that have allowed us to for human benefit.

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. Archie Mahan Prize of the Optical Society of America Dr. Hall was one of the first scientists to join JILA when it was established in 1962 (r to I) Edward W. Hagley, Charles W. Clark, and Lu Deng, Electron and Optical Physics

as a unique, interdisciplinary partner- Division, William D. Phillips, Atomic Physics Division, and Keith Burnett, Oxford University

ship between NBS and the University were awarded the Archie Mahan Prize of the Optical Society of America, "for authorship of Colorado. 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 Arthur S. Flemming Awards

Jun Ye, Quantum Leonard M. Hanssen, Optical Technology Division, received a 2002

Physics Division, Arthur S. Flemming Award, "for developing and establishing inno-

received a 2002 vative infrared technology for measuring optical properties of mate-

Presidential Early rials." These achievements have established NIST as the world leader

Career Award for in infrared measurement science and standards and have played

Scientists and a critical role in the success of U.S. defense and remote-sensing Engineers (PECASE), satellite systems dependent on state-of-the-art infrared technology.

"for pioneering research on laser interactions

Steven L. Rolston, Atomic Physics Division, received a 2002 with atoms and molecules and their applica-

Arthur S. Flemming Award, "for innovative leadership in the study tions to precision control and measurement

of new physical phenomena in ultra-cold atomic gases, including of light fields, matter waves, and optical

the first creation of ultra-cold plasmas and strongly-coupled plasmas." frequencies." This Presidential Award is the

Dr Rolston's research is part of the Laboratory's program to develop highest honor bestowed by the United States new laser cooling and trapping techniques and applications. Government on scientists and engineers beginning their independent careers. Sixty John H. Burnett, Atomic Physics Division, received a 2002 Arthur awards were given nationally and presented S. Flemming Award, "for developing and applying world-class by President George W. Bush in a White measurement systems critically needed for the design of advanced House ceremony. photolithography manufacturing tools." Dr. Burnett measured a

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

100 Top Young sufficiently large in candidate lens materials to prevent photolithog- Innovators raphy tools from focusing properly at the targeted wavelength of

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

Jun Ye was also chosen as one of the world's "100 Top Young Innovators" Service to America Medal by Technology Review, published by the

Massachusetts Institute of Technology. The Katharine B. Gebbie, Director of the Physics Laboratory, received

TR100, all individuals under 35 years of age, the 2002 Service to America Medal, "for career achievement," are recognized for their contributions to cosponsored by the Atlantic Media Company (Government technology. Dr. Ye's work is in the fields Executive Magazine, National Journal, and The Atlantic Monthly) of ultrasensitive high-resolution laser spec- and the Partnership for Public Service. She was cited for being the troscopy, cold atoms, continuous-wave founding director of the award-winning NIST Physics Laboratory, and ultrafast-pulse laser stabilization, pioneering the practical application of emerging technologies, enhancing scientific career and optical frequency standards. 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 American Physical Award Society's Outstanding Thesis Award

James C. Bergquist, Brian DeMarco was awarded the 2002 Outstanding Doctoral Thesis

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

Division, was recog- and Optical Physics (DAMOP). This award recognizes thesis research

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

William F. Meggars entitled "Quantum Behavior of an Atomic Fermi Gas," concerned

Award of the Optical the extension of the magnetic-trapping and evaporative-cooling tech-

Society of America niques used to produce atomic Bose-Einstein condensation to create

(OSA). The award is "for seminal contribu- the first quantum-degenerate Fermi gas of atoms. His work included measurements of the tions to high-resolution, high-accuracy atomic-collision mechanisms by which such gases reach thermal equilibrium. This work was

laser spectroscopy with applications to carried out at JILA, in collaboration with Dr Deborah Jin of the Quantum Physics Division. fundamental metrology and clocks." Dr DeMarco now has a postdoctoral appointment in the Ion Storage Group of the

Dr Bergquist developed the world's most Laboratory's Time and Frequency Division. stable laser and used it as the local oscilla- tor for an optical atomic clock based on a single mercury ion. This work is central Fellowship of the American Physical Society to the most accurate optical-frequency Zachary H. Levine, Electron and Optical Physics Division, was elected measurement ever made, and the first a Fellow of the American Physical Society "for leadership in demon- optical-frequency standard with a strating x-ray tomography of integrated circuit interconnects with microwave-frequency output. submicron resolution." Dr Levine has made both theoretical and

expehmental contributions to the field of high-resolution x-ray imag-

ing 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 retar-

dation on atomic collisions." Dr. Williams' work relates to the NIST

experimental program in laser cooling and trapping and is founda-

tional for the quantitative understanding of cold-atom collisions.

57 Sigma Xi (NIST Chapter) Sigma Xi Women of Color Award for Support to (NIST Chapter) Research Leadership Scientists Young Scientist Award Award

Anita K. Sweigert, IPippa--«i«Piip^ Eric L. Shirley, Maria E. Nadal,

Physics Laboratory Optical Technology Optical Technology

Office, received the Division, was recog- Division, received

NIST Chapter of nized with a 2002 the 2002 Women

Sigma Xi Award, "for Sigma Xi Young of Color Research

outstanding support Scientist Award, "for Leadership Award.

to NIST scientists." sustained excellence The award, given to

Ms. Sweigert serves as central coordinator in his contributions to the quantitative elite women in government and defense, of the NIST Summer Undergraduate theory of condensed-matter electronic honors Dr. Nadal, "for innovative research

Research Fellowship program (SURF), an structure." This award highlights his work and scientific leadership in optical proper- enormously successful, educational out- in condensed-matter (solid-state) theory, ties measurements in support of industry reach program aimed at providing which includes studies of x-ray absorption and government." The award is presented research opportunities to college and uni- by crystals. His calculations, based on the by Career Communications Group, Inc. versity students. The class of '02 had 102 electronic band structure of the crystals (CCG), publisher of U.S. Black Engineer students, selected from 195 applications. and including electron-(core) hole & Information Technology, and Hispanic

The students were placed in all seven NIST interactions, have proven to be the Engineer & Information Technology maga-

Measurement Laboratories. best in the world. zines. Dr. Nadal has developed new stan-

dards for reflectance and new measure-

ment services for such hard-to-character-

ize 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."

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 impor-

tant 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

optical ionizing radiation resulted in Dr. Coursey is recognized for his leadership in helping to protect with and technologies, has

first responders and the American public from terrorist attacks. numerous awards and recognition for the Laboratory's scientists

An expert in radiation measurement technology, he worked with and programs, including the Nobel Prize in 1997 and 2001.

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.

59 "

Silver Medal (DoC) Bronze Medal (NIST)

The Silver Medal is the second highest honor awarded by the The Bronze Medal is the highest honorary recognition available for

Department of Commerce, for "exceptional performance charac- Institute presentation. The award recognizes work that has result- terized by noteworthy or superlative contributions that have a ed in more effective and efficient management systems, as well direct and lasting impact. as the demonstration of unusual initiative or creative ability in the

development and improvement of methods and procedures. It is

(I to r) Eric L. Shirley, Optical Technology Division, John H. also given for significant contributions affecting major programs, Burnett, Atomic Physics Division, and Zachary H. Levine, scientific accomplishment within the Institute, and superior Electron and Optical Physics Division, received the Silver Medal, performance of assigned tasks for at least five consecutive years. "for advancing next-generation senniconductor lithography by the discovery of deep ultraviolet birefringence in calcium fluoride." Karen J. Combs, Physics Laboratory Office,

received the Bronze Medal, "for improving Through a combination of theoretical work and laboratory meas- NIST-wide administrative and technical urements, the team developed a precise understanding of the support." Mrs. Combs led a NIST-wide effect, and devised conceptual methods for engineering around administrative working group that promoted it. By providing an early warning to the semiconductor industry efficiencies in administrative policies and about a critical, previously neglected problem, the three scientists procedures, improved NIST-wide communica- smoothed the way for the timely introduction of the next tion among and between administrative disciplines, encouraged generation of microlithography 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 radio-

pharmaceutical standards." Dr. Zimmerman and his colleagues

provide the national standards for radionuclides used in diagnostic

and therapeutic nuclear medicine. To develop, maintain, and dis-

seminate 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 stan-

dard reference materials. He is also collabo-

rating 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 The Condon Award recognizes distinguished achievement in written exposition

acfiievement in the advancement of in science or technology.

measurement science or in the delivery

(r to I) Edward W. Hagley, Charles W. Clark, and Lu Deng, Electron and Optical of measurement services. Physics Division, William D. Phillips, Atomic Physics Division, and Keith Burnett, Oxford

Bert M. Coursey, University, were awarded the Condon Award, "for authorship of The Atom Laser, Optics

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

Division, received the matter-wave physics."

Astin Measurement

Science Award, "for

his leadership in devel-

oping 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 Edward Bennett Rosa Award (NIST)

radiation therapy. He improved dose stan- The Rosa Award recognizes outstanding achievements in the development of meaningful

dards used in all 1 1,000 mammography and significant standards of practice in the measurement field.

facilities in the Nation (26 million mam-

B. Carol Johnson, Optical Technology Division, received the Rosa mog rams/year). He led the development

Award, "for research and leadership in developing measurement stan- of radiation standards for brachytherapy

dards for ensuring the accuracy of remote-sensing instruments moni- used to prevent the closing of artenes

toring climate change." Dr. Johnson has developed novel optical radia- following angioplasty and to treat

tion measurement instruments, standards, and methods for ensuring prostate cancer (40,000 treatments/year).

the accuracy and reliability of satellite and ground-based instruments He initiated new measurement services for monitoring climate change. Her world-leading research program further supports the nuclear medicine applications for imaging remote sensing community by offenng training and education through formal courses, of tumors, infection, cardiac, or brain

lectures, and publications, and by providing instrument measurement validation through function (36,000 procedures/day), and for laboratory comparisons. Her efforts have accelerated the advancement of the fundamental radioimmunotherapy and bone palliation

metrology of optical radiation measurements, leading to the development of unique NIST (200,000 therapeutic procedures/year).

facilities for calibrating remote-sensing instruments.

61 Equal Employment Opportunity/Diversity Award (NIST) Safety 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 The Safety Award for Superior Accomplishment recognizes unusually significant successive rooms and interact with NIST contributions to the NIST Occupational Safety and Health program activities. scientists providing lively science demon- strations and supervising the girls' partici- (I to r) Timothy R Mengers, Occupational Health and Safety Division, Michael P. pation. The scouts also attend panel Unterweger and Bert M. Coursey, Ionizing Radiation Division, Zachary H. Levine, discussions where they can ask female Electron and Optical Physics Division, Stephen M. Seltzer, Ionizing Radiation Division,

G. Hobbs, Occupational Health and Safety Division, and Charles Clark, scientists what it is like to be a scientist. Thomas W.

Electron Optical Physics Division, the NIST Safety Award, "for prompt The volunteer program, now in its ninth and were awarded year, aims to increase the pipeline of action to enhance the security of NIST radiation sources and radioactive materials in the

." of terror of 1 , This young scientists. aftermath the attacks September 1 2001 group demonstrated excep-

tional 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 PHYSICS LABORATORY RESOURCES 1998 - 2002

Abbreviations: ($ MILLIONS)

SIRS - Congressionally appropriated 1999 2000 funds for NIST's Scientific and Technical

Research and Services STRS 33.1 34.7 34.8 37.1 39.9

ATP - Intramural research funds provided to support the goals of the NIST ATP 1.8 1.8 1.8 2.1 2.9 Advanced Technology Program

OA - Funds provided by other agencies OA 9.5 10.2 10.6 11.9 13.6 in support of research that they request

Other 3.8 3.7 4.4 4.5 5.0 Other - Other sources of funding, including calibration fees TOTAL 48.2 50.4 51.6 55.6 61.4 I J

Federal Agencies Representative Private Sector Collaborators Supporting Physics Laboratory Research American Association of Physicists Institute of Electrical and Electronics in Medicine Engineers

Department of Defense American National Standards Institute International Electrotechnical Commission National Aeronautics and Space American Physical Society Administration International Organization for American Society for Testing Standardization Department of Energy and Materials National Council on Radiation Department of Commerce Commission Internationale de I'fclairage Protection and Measurements Department of Health and Council for Optical Radiation NCSL International Human Services Measurements

Nuclear Energy Institute National Science Foundation Council on Ionizing Radiation

Environmental Protection Agency Measurements and Standards Optical Society of America

Department of Justice Electric Power Research Institute Optoelectronics Industry Development Association EUV LLC International SEMATECH Illuminating Engineering Society of North America 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

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