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Capability: Requires sample concentration of at least 0.05 mole in 2 m of solution. Magnetic field operates at 1.4T, corresponding to a resonance frequency of 15.08 MHz. Spinning resolution of 0.5 Hz over 10 mm sample tube; 90° rotation of magnetization requires pulse of <5μs duration and pulse programmer allows 180°-7-90° pulse sequence to be performed. A computer with 8000 words is available for accumulation and processing of data.

Applications: Identification of monomers and polymers in solution; identification of molecular rotational isomers; determination of polymer tacticity, cross-link and branches; determination of polymer chain dynamics in solution and in the solid state; determination of molecular conformation and structure of biopolymers and proteins.

Availability: The use of this instrument by NBS research workers on problems of mutual interest can be arranged. It must be operated only under the direct supervision of the scientist in charge of the instrument.

Contact: Dr. Darrell H. Reneker, Chief of Polymer Crystal Physics Section, Polymer Building, Room A209, Phone 301-921-3344.

GAS CHROMATOGRAPH-
MASS SPECTROMETER
SYSTEM

The gas chromatograph-mass spectrometer-computer system is designed for organic chemical applications, particularly trace organic analysis and structural identification. The system uses a quadrupole spectrometer and includes both electron impact and chemical ionization sources.

Capability: The gas chromatograph-mass spectrometer system is capable of measuring mass spectra with unit mass resolution from m/e 2 to 650 at a maximum scan speed of 325 amu/s. The gas chromatograph is equipped with linear temperature programming, dual column operation, thermal conductivity, flame ionization, and electron capture detectors. The mass spectrometer is controlled by a 16K word, 16 bit data acquisition and control system. The data system includes two 1.2 million word discs, programmable read-only memory, and an interactive display terminal. Both glass jet and membrane separators are available for the GC-MS interface.

Applications: Mass spectrometric analyses of gas chromatographic effluents from samples of biological and environmental origin are the predominant current applications. Other work in progress includes

isotope dilution mass spectrometry, precision quantitation for both electron impact and cher ionization, and spectrometric measurement and tification of impurities in Standard Reference Mat rials.

Availability: A limited amount of time is ava an for other groups and agencies. Laboratories with c. lenging analytical problems are encouraged to er into collaborative programs with the Section, pu ticularly in the areas of biological materials, cr analysis, and trace organic analyses in the env

ment.

Contact: Dr. Robert Schaffer, Chief of the Bio-organ Standards Section, Chemistry Building, Room At Phone 301-921-2866.

HIGH PRESSURE
PHOTOIONIZATION
MASS SPECTROMETER

This instrument combines a photoionization and re action chamber with a mass spectrometer in order investigate the interactions of positive ions with ne. tral molecules in the vapor phase.

Capability: Ionization of pure samples or mixture may be induced by photoabsorption at 8.4, 10.0, 1** 16.7, or 21.2 eV over the pressure range 10 to ap proximately 3 torr. Accurate rate constants are c tained at 300 K for bimolecular and relatively a termolecular reactions involving ion-neutral collis an processes. The kinetics of higher order processes cluding collisional stabilization and ionic solvat reactions may also be easily defined.

Applications: Determination of accurate rate com stants for ion-molecule reactions; effect of inter energy and pressure on reaction rates; elucidation: ionic polymerization mechanisms; analysis of tra components using chemical ionization techniques laboratory simulation of planetary ionospheres; sim ulation of gas phase radiolysis; determination of ior fragmentation patterns for correlation with pho": electron spectroscopy.

Availability: Contingent upon contract commitment and direction of in-house program. In appropr instances qualified scientists from NBS, other federa organizations, and private institutions may colab orate on problems of mutual interest to the opera tors.

Literature:

[1] J. Am. Chem. Soc. 91, 7627 (1969).

[2] J. Chem. Phys. 53, 794 (1970).

[3] J. Am. Chem. Soc. 92, 2937 (1970).

ontact: Dr. Pierre Ausloos, Chief of Radiation Chemtry Section, Chemistry Building, A-265, Phone 30121-2783.

HIGH RESOLUTION

NFRARED SPECTROMETER

his facility consists of a high resolution vacuum specometer with associated hardware and software to over the infrared region from 5.5 μm to 1.5 μm. The nstrument is available for measuring high resolution pectra of molecules in the gas phase.

Capability: This instrument operates in the spectral ange from 1850 cm-1 to 6000 cm-1 with a resolution of about 0.03 cm-1, a precision of measurement of ±0.002 cm-1, and an accuracy of measurement of bout ±0.006 cm-1. The entire optical path can be evacuated to eliminate absorption due to atmospheric constituents. Facilities are available for making measurements on gas samples in the temperature range rom -76°C to +1200°C. A variable long path absorption cell is also available, providing absorption paths up to 39 meters. The spectrometer output is recorded directly on magnetic tape, and software is available for processing the output on a digital computer to automatically provide an atlas listing the frequencies and intensities of absorption lines.

Applications: Fields of applications for these measurements are: air pollution, terrestrial and planetary atmospheric measurements, measurements on cool stars, molecular structure, studies of reaction intermediates and reaction products, flames and high temperature studies, thermodynamics, mechanisms of laser action, properties of chemical bonds, energy transfer mechanisms, and many more.

Availability: Instrument time is available for any projects which properly utilize the unique high resolution capabilities of this instrument.

Contact: Dr. Arthur Maki, Chief of Molecular Spectroscopy Section, Physics Building, Room B268, Phone 301-921-2021.

ISOTOPE RATIO

MASS SPECTROMETERS

The laboratory contains all the necessary chemical and mass spectrometric equipment for the determination of isotopic ratios at the "state of the art" ac

curacy level for all elements that will ionize by either surface or thermal methods.

Capability: The range of available equipment is such that almost any size sample down to 10-14 grams can be handled, for both absolute isotopic abundance ratio determinations or the determination of trace element concentration by isotope dilution.

Applications: Current applications include the determination of the absolute isotopic abundance ratios and atomic weights of the polynuclidic elements, the determination and certification of the absolute isotopic abundance ratios for standards of interest to the nuclear energy industry and the geochemist, the geochemical age determinations (Pb-U-Th, Rb-Sr) on lunar materials, and the determination of trace concentrations of a wide variety of elements in almost any conceivable matrix.

Availability: The facility is available to any qualified guest worker interested in high-accuracy analysis, but does require a three to six months training period.

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research into problems involving extensive development of microwave instrumentation. Pioneering efforts in the study of transient and high temperature molecules have led to designs and techniques which affect spectrometer performance in many ways. Operational flexibility and sensitivity have been significantly extended in both the high and low frequency extremes of the traditional microwave region.

Capability: Two separate spectrometer systems are available with klystron sources and requisite hardware to cover the complete range from 2 to 132 GHz. Harmonic generation equipment extends the operation further into the millimetre region. Conventional septum-type waveguide absorption cells, used for studies of static systems, include a 12 ft gold-plated cell (3.3 GHz cutoff), 15 ft brass cell (8 GHz cutoff), and 4 ft all-stainless and Teflon cell for special handling of reactive gases (12 GHz cutoff). All three conventional cells can be cooled to dry ice and the special stainless cell may be heated to 300°C. Several parallel plate cells are available complete with discharge and pyrolysis sample generating apparatus and fast-continuous-flow vacuum systems. Special ovens will allow operating temperatures to 1000°C for certain experiments.

Applications: Analyses of rotational spectra of polar gas-phase molecules yielding structural parameters, electric dipole moments, quadrupole coupling constants and spectroscopic details such as vibrationrotation interactions, etc. Stable molecules with vapor pressures of a few micrometres of Hg at temperatures below 1000°C are readily accessible. A variety of small transient molecules with lifetimes of the order of 10 ms have been successfully studied in the flow systems. Certain laser-microwave double resonance and laser pumped reaction systems are also within the range of capabilities.

Availability: To qualified research workers on a collaborative basis with NBS staff or in special cases where background and experience is adequate on a guest worker basis. It should be emphasized that these spectrometer systems are hand-built, state-ofthe-art devices and require extended experience for competent operation.

Contact: Dr. Donald R. Johnson, Molecular Spectroscopy Section, Physics Building, Room B268, Phone 301-921-2021.

MÖSSBAUER

SPECTROSCOPY OF METALS

and electronic environment of an atom embedded in a solid material. By detecting the conversion ele: trons that emanate from a sample, very thin surface layers can be studied. Differences between the su face and bulk can be observed by also detecting the primary Mössbauer effect gamma rays.

Capability: Solid specimens of irregular shapes w outside dimensions up to 30 cm can be utilized. M mum size is about 0.5 cm diameter and 5μm tha ness. Transmission spectra can be obtained (on pow ders or foils) as a function of temperature in apples magnetic fields up to 50kG. On selected specimen time delayed perturbed angular correlation stude can also be made.

Applications: Measurements of isomer shifts, mat netic hyperfine fields and electric field gradients per mit studies of phase composition, magnetic proper ties, electronic structure and diffusion. Application to corrosion studies, surface effects, and other meta lurgical problems.

Availability: To any qualified NBS research worker In appropriate instances, researchers from other ganizations can gain access to the facility. Scientist from U.S. universities, federal agencies and ind tries, and from abroad have qualified to use th equipment in the past.

Literature:

[1] Nuclear Resonances in Metals: NMR and Mössbauer Effect by I. D. Weisman, L Swartzendruber and L. H. Bennett in Meas urement of Physical Properties, E. Passag and R. F. Bunshah, Editors. (Wiley-Inter science, New York), V. 6(2), 1973. [2] Mössbauer Spectrometer Calibration Us TiFe, Nat. Bur. Stand. (U.S.) Tech. News B 54, No. 10, page 239 (1970).

Contact: Dr. L. H. Bennett, Alloy Physics Sector Materials Building, Room B-150, Phone 301-921-2

MULTICHANNEL

FLAME SPECTROMETER

This flexible system was designed and assembled a NBS to perform precise spectral measurements the emission and atomic absorption modes us flames or similar high temperature "thermostates The spectrometer used to detect the radiations or inating from the excitation source is a conventiona

1-m grating instrument, arranged to focus on a pho

Mössbauer effect utilizes the nuclear properties of or a metal pa

various isotopes to probe the local chemical, magnetic

with eight exit slits.

Capability: Operable as a spectrograph, a scanning monochromator, or multichannel instrument. Measures in emission and atomic absorption modes for one element at a time, or up to 8 chemical species simultaneously. The output is either analog or digital. Applications: Analysis for alkali and earth alkali metals in body fluids, agricultural products, soils, air, te and water samples; for elements from the I to VIII groups in alloys; for trace elements such as Pb, Cd, Hg, Cu, Cr, Ni.

Availability: To any qualified NBS research worker, after an initial training period by R. Mavrodineanu. Literature:

[1] R. Mavrodineanu, Discussion of some ex-
perimental and fundamental flame spectro-
scopy, Revue GAMS, 1971, no. 3, 39-60.
[2] R. Mavrodineanu and H. Boiteux, Flame
Spectroscopy, John Wiley and Sons, 1965,
pp. 721.

Contact: Dr. R. Mavrodineanu, Assistant Chief, Spectrochemical Analysis Section, Chemistry Building, Room B-218, Phone 301-921-2141.

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

The NMR method makes use of the magnetic and electric moments of atomic nuclei to probe the local environment about selected nuclei in materials. Appropriate nuclei of virtually any chemical element can be used, but considerations such as isotopic abundance, sensitivity and atomic motion restrict studies to preselected problems.

Capability: Metallic specimens generally should be in the form of -325 mesh powder, but other forms including single crystals are possible. Wide-line NMR spectroscopy with laboratory electromagnet and high-power pulsed NMR spectroscopy with superconducting magnet. Data acquisition system used for sensitivity enhancement. Ferromagnetic NMR spectroscopy also available. Temperature and pressure variations possible.

Applications: Measurements of Knight shifts, relaxation times, electric quadrupole interactions and lineshapes permit studies of electronic structure, defect structure and diffusion. These have been important primarily in the study of metals, alloys, and intermetallic compounds but occasional attention has been given to practical problems outside of metallurgy such as detecting cancer in live mice utilizing

NMR.

Availability: To any qualified NBS research worker. In appropriate instances, researchers from other organizations can gain access to the facility. Scientists from U.S. universities, federal agencies and industries, and from abroad have qualified to use this equipment in the past.

Literature: Nuclear Resonances in Metals: NMR and Mössbauer Effect by I. D. Weisman, L. J. Swartzendruber and L. H. Bennett in Measurement of Physical Properties, E. Passaglia and R. F. Bunshah, Editors. (Wiley-Interscience, New York, V. 6(2), 1973.

Contact: Dr. Lawrence H. Bennett, Chief of Alloy Physics Section, Materials Building, Room B150, Phone 301-921-2982.

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greatly enhancing the beam intensity. The wavelength of neutrons used in this spectrometer can be varied from 1.5Å to 4.0Å in order to optimize the resolution with the sample attentuation characteristics.

Applications: This spectrometer has applications in
the determination of shape, size and interaction of
macromolecules as well as similar properties of de-
fects in materials, magnetic correlations at extended
distances, and density fluctuations near the critical
point of phase transitions. Neutron small-angle scat-
tering has particular application to submicroscopic
particles of low population densities, where light and
x-ray scattering suffer from absorption and poor res-
olution.

Availability: Instrument time can be scheduled for
appropriate experiments of projects of NBS staff, after
the proposed measurements are reviewed by the
Users Committee for these facilities. Outside users
can also be accommodated depending on the type of
measurements and the available resources.
Literature:

NBS Reactor: Summary of Activities, Oct. 1971-
Sept. 1972, Nat. Bur. Stand. (U.S.) Tech. Note
758 (Mar. 1973).

Contact: Dr. Robert Carter, Chief, Reactor Radiation
Division, Materials Building, Room A106, phone 301-
921-2421.

NUCLEAR IRRADIATION
FACILITIES

Capability: An extensive number of well-characterized irradiation facilities offer a wide range of neutron and/or gamma environments to levels exceeding 1011 neutrons per square centimeter per second. These include five distinct pneumatic facilities, eleven in-core vertical thimbles with inside diameters up to 31⁄2 inches, and seven vertical reflector thimbles with 42 inch openings. These facilities are used simultaneously and can accommodate tens of thousands of samples a year.

Applications: Most common use is in neutron activation analysis for detection of trace elements in parts per million, billion, or trillion. Other uses include preparation of isotopes for tracer work, preparation of isotopes for medicine, production of gamma and positron sources, studies of radiation damage, and the characterization of standard reference materials.

Availability: All facilities are available to qualified scientists. Each sample to be irradiated must be ac

companied by an irradiation proposal form for se review. The packaging of each sample must be proved by the staff of the Reactor Operations Sect.c who can also provide guidance in the preparation: the irradiation proposals.

Literature: W. F. Sheely, The NBS Reactor: Its Descrp tion and a Guide to Its Use by Experimenters, No: Rept. 9081 (1966).

Contact: Tawfik M. Raby, Deputy Chief, Reactor Rà diation Division, Reactor Building, Room A137, Phone 301-921-2523.

TIME-OF-FLIGHT

NEUTRON SPECTROMETERS

This instrumentation utilizes either crystal monochremators or phased-choppers to select monoenerge": neutrons, which are scattered by a sample and de tected 2.5 to 3.8 metres away by multiple neutron detectors at scattering angles between 10° and 105 The energy of the scattered neutrons is determined by time-of-flight analysis.

Capability: The spectrometers provide incident ne tron beams ranging in energy between 3 meV 2 cm-1) and 100 meV (800 cm-1) and cover a spectra range for inelastic scattering of 0.5 meV to 100 me (4 to 800 cm-1). The available resolution varies from 0.2 meV (at the lowest energies) to 5 meV. The range of momentum transfers (Q) for elastic scattering from 0.2Å1 to 10Å. The time-of-flight data colec tion is automatic, utilizing either a multichannel ana lyzer or a small computer. The spectrum is continu ously observable on a scope and the data can be printed out on paper tape or on a typewriter. A spe cially designed sample cryostat is available for spec trum measurements on solid and liquid samples be tween 5 and 300K.

Applications: The spectrometers can be used wide. in the study of the dynamics of liquids and solic Some applications include the study of crystal and molecular dynamics of solids, vibrational spectra glasses, hydrogen diffusion in metals, orientationa disorder and relaxation processes in polymers and molecular crystals, and the dynamics of liquids.

Availability: Instrument time can be scheduled to appropriate experiments or projects of NBS sta after the proposed measurements are reviewed by the Users Committee for these facilities. Outs.c users can also be accommodated depending type of measurements and available resources.

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