amination of various body fluids and solids, and for other measurements involving health problems. This instrument is used to certify colored glass filters (SRM) 930) between 300 and 700 nm, at three transmittance levels to within an uncertainty of one part in 101 T units. Ampoules containing solutions (SRM 931) are particularly designed to be used in conjunction with flow-type spectrophotometers in both visible and ultraviolet regions. These SRM's were developed to meet the particular needs expressed by clinical chemists organizations. The technique is also widely used for environmental studies of smog, stack emissions, stream pollutants, and atmospheric contaminants. Availability: Only limited time is presently available for other agencies, because of the SRM certification program, research on stable materials, reproducible methods for transmittance measurements, spectral bandwidth and stray light determinations. Literature: [1] R. Mavrodineanu, NBS J. Res. 76A, No. 5, 405-425 (Sept.-Oct. 1972); NBS Tech. News Bull. 56, No. 7, pages 166-167 (July 1972). [2] R. Mavrodineau, Spectrophotometry Instrument Development, NBS Tech. Note 584, pp. 9-21, (June 1971). [3] R. N. Rand, Practical Photometric Standards, Clinical Chemistry 15, 839-863 (September 1969). Contact: Dr. Oscar Menis, Chief, Spectrochemical Analysis Section, Room B224, Chemistry Building, phone 301-921-2175. CONCAVE GRATING The Spectroscopy Section has three 10.7-m concave grating spectrographs for use in different portions of the photographic region: 1. About 200 to 900 Å—air region, normal inci dence 2. About 450 to 2500 Å-vacuum ultraviolet region, normal incidence 3. About 75 to 600 Å-vacuum ultraviolet re gion, grazing incidence at 10°. These instruments can be used for the photographic recording of all types of atomic and molecular spectra. Capability: The 10.7-m concave gratings with 1200 grooves/mm give resolving powers of over 150,000 and plate factors of about 0.77 Å/mm in the first spectral order of the normal incidence instruments. The plate factor of the grazing incidence spectrograph varies from 0.17 Å/mm at 70 Å to 0.32 Å/mm at 600 Å. Applications: These spectrographs have been used in conjunction with mild discharge light sources for the photographic recording of the spectra of neutral and single ionized spectra of a wide variety of elements, and in conjunction with spark discharges for the similar acquisition of highly-ionized spectra. Availability: To any qualified research worker. In the immediate past, guests from Kitt Peak, Naval Research Laboratory, Canada, The Netherlands, and France, have used the spectrographs. Contact: Dr. William C. Martin, Jr., Chief of Spectroscopy Section, Physics Building, Room A167, Phone 301-921-2011. CZERNY-TURNER HIGH DISPERSION SPECTROGRAPH This is a high resolution, high dispersion, stigmatic, plane grating spectrograph. The grating is 220 X 135-mm, has 300 grooves/mm, and is blazed at 63°26′ (6μm). It is used in the fifth to the thirtieth order. A predisperser used in conjunction with this spectrograph separates or eliminates overlapping orders. Capability: The resolving power of the instrument is about 700,000 at 4000 Å (fifteenth order). The plate factor is about 3.6/n Å/mm (n order number). The instrument can be used from 2000 to 12000Å. Applications: This instrument has been used for a wide variety of atomic and molecular spectroscopic studies for which high resolution was necessary. The stigmatic property of the spectrograph is useful for spectral separation in types of discharges where different ions are excited in different areas. It can be used for cross-dispersion with interferometers. Availability: To any qualified research worker. In the immediate past, guests from Kitt Peak, Naval Research Laboratory, Canada, The Netherlands, and France, have used the spectrograph. Literature: [1] J. Reader, L. C. Marquet, and S. P. Davis, Predisperser for high-resolution grating spectrographs, Appl. Optics, 2, 963 (Sept. 1963). [2] J. Reader, Optimizing Czerny-Turner Spectro graphs, J. Opt. Soc. Amer. 59, no. 9, 11891196 (Sept. 1969). Contact: Dr. William C. Martin, Jr., Chief of Spectroscopy Section, Physics Building, Room A167, Phone 301-921-2011. ELECTRON ENERGY Three state-of-the-art electron energy loss spectrometers allow measurements of the energy loss spectra of gases with an energy resolution of 15 to 50 milli-electron volt with incident energies from threshold to several hundred electron volts. Capabilities: Energy loss spectra of gases. Excitation functions near threshold. Analysis of gas mixtures. The spectrometers are controlled and data taken by an Interdata 70 computer. Computer programs for gas analysis and for plotting of data are available. Availability: Because of the complexity of instrumentation, the direct use of these spectrometers is limited to: (a) permanent members of the laboratory; and (b) qualified full-time guest scientists with appointments exceeding six months. The spectrometers may be used indirectly through cooperative or contractual research agreements. Literature: [1] R. Celotta, S. R. Mielczarek, and C. E. Kuyatt, NBS Report 10 915 (September 1972). [2] N. Swanson, C. E. Kuyatt, J. W. Cooper and M. Krauss, Phys. Rev. Letters 28, 948 (1972). [3] G. E. Chamberlain, S. R. Mielczarek and C. E. Kuyatt, Phys. Rev. A 2, 1905 (1970). Contact: Dr. Chris E. Kuyatt, Chief, Surface and Electron Physics Section, Metrology Building, Room B214, Phone 301-921-2051. FAR INFRARED SPECTROSCOPY Far infrared spectroscopy studies the absorption, transmission or reflection of long wavelength, 1000μ to 10μ (10-10 nm), electromagnetic radiation which is caused by vibrations, rotations, and translations which modulate the dipole moment of the atoms and molecules in the sample. It is a useful tool for the identification of molecular or ionic species in the liquid, solid, and gaseous states. Capability: The techniques of Fourier transform spectroscopy are applied in the far infrared instrument. The range of 10-1000 cm-1 can be measured with a resolution of 0.5 cm-1. The radiation detector is a triglycine sulfate (TGS) pyroelectric crystal. The Michelson interferometer employs a high precision air bearing translator, and a He-Ne laser is used for distance measurement. Data output is typically graphical and is processed by an on-line computer which also serves to control the instrument throughout the experiment. Specimens can be studied by transmission or reflection as is necessary. Facilities are provided for sample temperature variation between 10 K and 300 K and for matrix isolation. Applications: Molecular and crystal dynamics as displayed by translational, rotational, librational and vibrational degrees of freedom are measured as a function of parameters such as temperature, pressure, stoichiometric relations, electric or magnetic fields, concentration and phase. Typical applications involve the spectra of matrix isolated free radicals and molecules, lattice and molecular dynamics of polymers, phase transitions in solids (including melting), studies of isomerism, vibrational and rotational studies in gases, investigation of stoichiometry in crystals and disordered solids, and measurements of chemical reaction products. Availability: The instrument is available to qualified research workers, following a training period in its use. Proposed research projects require the approval of the instrument manager, or in special cases, of the users committee. Literature: [1] G. Horlick, Appl. Spectrosc. 22, 617 (1968). [2] P. R. Griffiths, C. T. Foskett, and R. Curbelo, Appl. Spectrosc. Revs. 6, 31 (1972). Contact: Dr. Marilyn E. Jacox, Act. Chief, Photochemistry Section, Chemistry Building, Room A243, Phone 301-921-2754. FLAME EMISSION SPECTROMETER WITH REPETITIVE OPTICAL SCANNING Repetitive optical scanning for flame emission spectrometry provides a unique way of minimizing spectral interferences in matrices and flame gases. By measuring the second derivative of the output intensity, a small signal from an atomic emission line can be readily discerned from a very large continuum. This is especially useful when dealing with the high temperature flames and plasmas which are needed to excite the more refractory elements. At the same time this technique requires a minimum of sample. Capabilities: The instrument provides the capability of quantitative measurements at the parts per million level or less for thirty elements in a large variety of matrices with a precision of 0.2 to 5 percent. For many of these analyses only 50 μl of solution is necessary per analysis. Application: This instrument is presently being used to characterize many of the trace elements in Standard Reference Materials and other related materials. Typical examples include Li, Na, K and Ca in serum, liver, orchard leaves, fertilizer and clays; Ca, Sr and Ba in steels; Al in high purity steel and phosphate rock; Li in both fresh and sea water; Zr, La and Sr in optical quality glass; Ni and Co in steels and ores; Gd in calcium fluoride; Pd and Ru in alloys and TI in organic compounds. Availability: To any qualified research worker, but because of the complexity of the instrument and safety in the handling of high temperature flames and plasmas, the operation of the facility is limited. to permanent members of the Spectrochemical Analysis Section. Literature: [1] W. Snelleman, T. C. Rains, K. W. Yee, H. D. Cook, and O. Menis, Flame emission spectrometry with repetitive optical scanning in the derivative mode, Anal. Chem., 42, 394 (1970). [2] O. Menis, editor, Flame emission and atomic absorption spectrometry, NBS Technical Note 504 (1969), pp. 1-8. [3] O. Menis and J. I. Shultz, editors, Analytical flame spectroscopy, NBS Technical Note 544, (1970), pp. 58-86. Contact: Theodore C. Rains, Spectrochemical Analysis Section, Chemistry Building, Room B221, Phone 301921-2142. NBS facility for the production and subsequent kinetic detection of reactive atomic and free radical species incorporates such fluorescence techniques. and is the precursor of several similar pieces of apparatus in chemical laboratories throughout the world. Capability: Gas mixtures of an atom or free-radical source compound, reactant substrate, and inert diluent (from 1 torr to 1 atm in total pressure) are subjected to a flash pulse (electrical discharge or laser). The atoms or free radicals photolytically produced are subjected to the cw radiation of a microwave resonance flow lamp or the delayed pulsed radiation of a suitable laser. The scattered radiation is subsesequently monitored as a function of time to obtain the kinetic history of the reactive species. Experiments can be conducted at temperatures ranging from 200 to 500 K. Applicability: The technique is presently suited for the study of chemical dynamics of systems involving H, O, N, S, CI, C, and Br atoms as well as OH radicals. With suitable resonance lamp development, the technique can be extended to numerous other reactive species. The range of experimental conditions. overlaps those desired for investigations involving air pollution, combustion processes, planetary atmosphere, chemical laser systems, etc. Availability: The apparatus is presently being used full-time for chemical kinetics studies of atmospheric interest. Outside use is consequently restricted to short-term problems suitable for study on a cooperative basis. Literature: [1] E. L. Baardsen and R. W. Terhune, Appl. Phys. [2] M. J. Kurylo, J. Phys. Chem. 76, 3518 (1972). Contact: Dr. Michael J. Kurylo, Photochemistry Section, Chemistry Building, Room A253. Phone 301921-2080. FLASH PHOTOLYSIS RESONANCE FLUORESCENCE APPARATUS Fluorescence measuring techniques have proven to be quite sensitive and versatile for the detection and monitoring of many short-lived species. The existing FOURIER TRANSFORM NUCLEAR MAGNETIC RESONANCE SPECTROMETER This high-resolution instrument utilizes the magnetic moment of 13C nuclei to probe the molecular dynamics and structure of biological and commercial polymeric materials. 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- 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 of quantitation for both electron impact and chemical ionization, and spectrometric measurement and identification of impurities in Standard Reference Materials. Availability: A limited amount of time is available for other groups and agencies. Laboratories with challenging analytical problems are encouraged to enter into collaborative programs with the Section, particularly in the areas of biological materials, clinical analysis, and trace organic analyses in the environ ment. Contact: Dr. Robert Schaffer, Chief of the Bio-organic Standards Section, Chemistry Building, Room A367, Phone 301-921-2866. HIGH PRESSURE MASS SPECTROMETER This instrument combines a photoionization and reaction chamber with a mass spectrometer in order to investigate the interactions of positive ions with neutral molecules in the vapor phase. -4 Capability: Ionization of pure samples or mixtures may be induced by photoabsorption at 8.4, 10.0, 11.7, 16.7, or 21.2 eV over the pressure range 10-1 to approximately 3 torr. Accurate rate constants are obtained at 300 K for bimolecular and relatively fast termolecular reactions involving ion-neutral collision processes. The kinetics of higher order processes including collisional stabilization and ionic solvation reactions may also be easily defined. Applications: Determination of accurate rate constants for ion-molecule reactions; effect of internal energy and pressure on reaction rates; elucidation of ionic polymerization mechanisms; analysis of trace components using chemical ionization techniques; laboratory simulation of planetary ionospheres; simulation of gas phase radiolysis; determination of ionic fragmentation patterns for correlation with photoelectron spectroscopy. Availability: Contingent upon contract commitments and direction of in-house program. In appropriate instances qualified scientists from NBS, other federal organizations, and private institutions may collaborate 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). Contact: Dr. Pierre Ausloos, Chief of Radiation Chemistry Section, Chemistry Building, A-265, Phone 301921-2783. HIGH RESOLUTION INFRARED SPECTROMETER This facility consists of a high resolution vacuum spectrometer with associated hardware and software to cover the infrared region from 5.5 μm to 1.5 μm. The instrument is available for measuring high resolution spectra of molecules in the gas phase. Capability: This instrument operates in the spectral range from 1850 cm-1 to 6000 cm-1 with a resolution of about 0.03 cm-1, a precision of measurement of ±0.002 cm1, and an accuracy of measurement of about ±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 from 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. Literature: |