Windowless x-ray tube spectrometer for light element analysis.
Windowless tube spectrometer for x-ray fluorescent analysis of light elements down through fluorine
X-RAY FLUORESCENCE SPECTROSCOPY↗
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Computer controlled X-ray spectrometeric analysis of geological materials
Digital computer controlled X ray fluorescent spectroscopy of geological materials
Weyler, P. A.↗
Laser induced fluorescence applied to turbulent reacting flows
The saturated fluorescence method makes use of the great simplifications which occur when under conditions of intense radiation the excitation process becomes saturated. A description is presented of the saturated fluorescence method, taking into account rate equations and saturation, radiative transfer, the two-level system, a multilevel system, and measurements under saturation conditions. The detectability limits of the method are investigated. Fluorescence trapping is found to place an upper limit on the number density of the fluorescing species that can be measured without signal loss. Turbulence places time and spatial constraints on the measurements, but otherwise poses no difficulties. Saturated laser induced fluorescence spectroscopy appears to be a most promising method for measuring species concentrations in flames.
Daily, J. W.↗
Oceanic Lidar
Instrument concepts which measure ocean temperature, chlorophyll, sediment and Gelbstoffe concentrations in three dimensions on a quantitative, quasi-synoptic basis were considered. Coastal zone color scanner chlorophyll imagery, laser stimulated Raman temperaure and fluorescence spectroscopy, existing airborne Lidar and laser fluorosensing instruments, and their accuracies in quantifying concentrations of chlorophyll, suspended sediments and Gelbstoffe are presented. Lidar applications to phytoplankton dynamics and photochemistry, Lidar radiative transfer and signal interpretation, and Lidar technology are discussed.
Carder, K. L.↗
A survey of simulation and diagnostic techniques for hypersonic nonequilibrium flows
The possible means of simulating nonequilibrium reacting flows in hypersonic environments, and the required diagnostic techniques, are surveyed in two categories: bulk flow behavior and determination of chemical rate parameters. Flow visualization of shock shapes for validation of computational-fluid dynamic calculations is proposed. The facilities and the operating conditions necessary to produce the required nonequilibrium conditions, the suitable optical techniques, and their sensitivity requirements, are surveyed. Shock-tubes, shock-tunnels, and ballistic ranges in a wide range of sizes and strengths are found to be useful for this purpose, but severe sensitivity requirements are indicated for the optical instruments, which can be met only by using highly-collimated laser sources. Likewise, for the determination of chemical parameters, this paper summarizes the quantities that need to be determined, required facilities and their operating conditions, and the suitable diagnostic techniques and their performance requirements. Shock tubes of various strengths are found to be useful for this purpose. Vacuum ultraviolet absorption and fluorescence spectroscopy and coherent anti-Stokes Raman spectroscopy are found to be the techniques best suited for the measurements of the chemical data.
Sharma, Surendra P.↗
High-Resolution Detector For X-Ray Diffraction
Proposed x-ray-sensitive imaging detector offers superior spatial resolution, counting-rate capacity, and dynamic range. Instrument based on laser-stimulated luminescence and reusable x-ray-sensitive film. Detector scans x-ray film line by line. Extracts latent image in film and simultaneously erases film for reuse. Used primarily for protein crystallography. Principle adapted to imaging detectors for electron microscopy and fluorescence spectroscopy and general use in astronomy, engineering, and medicine.
Carter, Daniel C.↗
Laser Diagnostics for combustion temperature and species measurements
Laser optical diagnostic techniques for the measurement of combustion gaseous-phase temperatures and, or species concentrations are discussed. The techniques fall into two classes: incoherent (Rayleigh scattering, spontaneous Raman scattering, laser induced fluorescence spectroscopy) and coherent (coherent anti-Stokes Raman spectroscopy). The advantages, disadvantages and applicability of each method are outlined.
Eckbreth, Alan C.↗
The permanent electric dipole moment of chromium monoxide
The permanent electric dipole moments for the X 5Pi and B 5pi states of gas-phase CrO have been experimentally determined using the sub-Doppler optical technique of intermodulated fluorescence spectroscopy in conjunction with the Stark effect. The measured values are 3.88 + or - 0.13 and 4.1 + or - 1.8 D for the X and B states, respectively. The theoretical values determined for the X state using multireference CI iterative-natural-orbital and finite-field calculations are in excellent agreement with the experimental value.
Steimle, Timothy C.↗
Production of N(+)-asterisk from N2 + hnu - Effective EUV emission yields from laboratory and dayglow data
Photodissociative ionization of N2 into the unbound N2(+) H 2Sigma-g(+) state is identified as the parentage of a number of N(+) and N-excited states that contribute to the u.v. dayglow. Yields have been obtained for the production of extreme ultraviolet emission lines of N(+) and N from a laboratory experiment using a broadband synchrotron radiation source with fluorescence spectroscopy. The yields are termed 'effective', in that they are constant percentages of the H state cross section. These are compared wih effective yields needed to reproduce N II 1085 and 916 A lines from four dayglow observations using a model of solar energy deposition and photoelectron production and loss in the earth's thermosphere. The 1085 A effective yield measured in the laboratory (18 percent) agrees with that from the dayglow data (average of 17 percent) to well within experimental uncertainties. Thus, it is concluded that photodissociative ionization of N2 is the primary source of the N II 1085 A dayglow. However, there is an order of magnitude discrepancy among the various dayglow observations of the 1085/916 intensity ratio, only one of which is consistent with the laboratory observation of 4.4. Neither contamination by other dayglow features nor atmospheric extinction can account for the disparities. Laboratory measurements of N2 and O2 absorption cross sections at these wavelengths are also reported.
Meier, R. R.↗
Use of T7 RNA polymerase to direct expression of outer Surface Protein A (OspA) from the Lyme disease Spirochete, Borrelia burgdorferi
The OspA gene from a North American strain of the Lyme disease Spirochete, Borrelia burgdorferi, was cloned under the control of transciption and translation signals from bacteriophage T7. Full-length OspA protein, a 273 amino acid (31kD) lipoprotein, is expressed poorly in Escherichia coli and is associated with the insoluble membrane fraction. In contrast, a truncated form of OspA lacking the amino-terminal signal sequence which normally would direct localization of the protein to the outer membrane is expressed at very high levels (less than or equal to 100 mg/liter) and is soluble. The truncated protein was purified to homogeneity and is being tested to see if it will be useful as an immunogen in a vaccine against Lyme disease. Circular dichroism and fluorescence spectroscopy was used to characterize the secondary structure and study conformational changes in the protein. Studies underway with other surface proteins from B burgdorferi and a related spirochete, B. hermsii, which causes relapsing fever, leads us to conclude that a strategy similar to that used to express the truncated OspA can provide a facile method for producing variations of Borrelia lipoproteins which are highly expressed in E. coli and soluble without exposure to detergents.
Dunn, John J.↗
Green icebergs formed by freezing of organic-rich seawater to the base of Antarctic ice shelves
Samples of Antarctic seawater, basal ice, and green ice from ice cliffs and green icebergs are analyzed in order to examine green icebergs formed by the freezing of organic-rich seawater to the base of Antarctic ice shelves. Spectral reflectance of a green iceberg measured near 67 deg S, 62 deg E confirms that the color is inherent in the ice, not an artifact of the illumination. A constituent that absorbs blue photons is identified by spectrophotometric analysis of core samples from this iceberg and from the Amery basal ice, and of seawater samples from Prydz Bay off the Amery Ice Shelf. Analysis of the samples by fluorescence spectroscopy indicates that the blue absorption, and hence the inherent green color, is due to the presence of marine-derived organic matter in the green iceberg, basal ice, and seawater. Thick accumulations of green ice, in icebergs, and at the base of ice shelves indicate that high concentrations of organic matter exist in seawater for centuries at the depth of basal freezing.
Warren, Stephen G.↗
High-Temperature Optical Window Design
A high-temperature optical window is essential to the optical diagnostics of high-temperature combustion rigs. Laser Doppler velocimetry, schlieren photography, light sheet visualization, and laser-induced fluorescence spectroscopy are a few of the tests that require optically clear access to the combustor flow stream. A design was developed for a high-temperature window that could withstand the severe environment of the NASA Lewis 3200 F Lean Premixed Prevaporized (LPP) Flame Tube Test Rig. The development of this design was both time consuming and costly. This report documents the design process and the lessons learned, in an effort to reduce the cost of developing future designs for high-temperature optical windows.
Roeloffs, Norman↗
Thermochemistry and Kinetics of the Cl+O2 Association Reaction
Laser flash photolysis of Cl2/O2 mixtures has been employed in conjunction with Cl((sup 2)P(sub 3/2)) detection by time-resolved fluorescence spectroscopy to investigate equilibration kinetics for the reactions Cl + O2 + O is in equilibrium with ClOO + O2 at temperatures of 181-200 K and O2 pressures of 15-40 Torr. The third-order rate coefficient for the association reaction at 186.5 +/- 5.5 K is (8.9 +/- 2.9) x 10(exp -33) cm(exp 6) molecule(exp -2) s(exp -1) and the equilibrium constant (K(p)) at 185.4 K is 18.9 atm(exp -1) (factor of 1.7 uncertainty). A third law analysis of our data leads to a value for the Cl-OO bond dissociation energy of 4.76 +/- 0.49 kcal mol(exp -1).
Nicovich, J. M.↗
Kinetics and Thermochemistry of ClCO Formation from the Cl + CO Association Reaction
Laser flash photolysis of Cl2/CO/M mixtures (M = N2, CO, Ar, CO2) has been employed in conjunction with Cl((sup 2)P(sub J)) detection by time-resolved resonance fluorescence spectroscopy to investigate equilibration kinetics in the reactions Cl((sup 2)P(sub J)) + CO ClCO as a function of temperature (185-260 K) and pressure (14-200 Torr). The association and dissociation reactions are found to be in the low-pressure limit over the range of experimental conditions investigated. In N2 and/or CO buffer gases, the temperature dependences of the ClCO formation and dissociation reaction rate constants are described by the Arrhenius expressions k(sub 1) = (1.05 +/- 0.36) x 10(exp -34) exp[(810 +/- 70)/T] cm(exp 6)/molecules(exp 2).s and k(sub -1) = (4.1 +/- 3.1) x 10(exp -10) exp[(-2960 +/- 60)/T]cu cm/(molecule.s) (errors are 2 sigma). Second- and third-law analyses of the temperature dependence of the equilbrium constant (k/k-1) lead to the following thermodynamic parameters for the association reaction: Delta-H(sub 298) = -7.7 +/- 0.6 kcal/mol, Delta-H(sub 0) = -6.9 +/- 0.7 kcal/mol, Delta-S(sub 298) = -23.8 +/- 2.0 cal/mole.K, Delta-H(sub f,298)(ClCO) = 5.2 +/- 0.6 kcal/mol (errors are 2 sigma). The results repported in this study significantly reduce the uncertainties in all reported kinetic and thermodynamic parameters.
Nicovich, J. M.↗
Kinetics of the Br2-CH3CHO Photochemical Chain Reaction
Time-resolved resonance fluorescence spectroscopy was employed in conjunction with laser flash photolysis of Br2 to study the kinetics of the two elementary steps in the photochemical chain reaction nBr2 + nCH3CHO + hv yields nCH3CBrO + nHBr. In the temperature range 255-400 K, the rate coefficient for the reaction Br((sup 2)P(sub 3/2)) + CH3CHO yields CH3CO + HBr is given by the Arrhenius expression k(sub 6)(T) = (1.51 +/- 0.20) x 10(exp -11) exp(-(364 +/- 41)/T)cu cm/(molecule.s). At 298 K, the reaction CH3CO + Br2 yields CH3CBrO + Br proceeds at a near gas kinetic rate, k(sub 7)(298 K) = (1.08 +/- 0.38) x 10(exp -10)cu cm/(molecule.s).
Nicovich, J. M.↗
Temperature Dependence of the O + HO2 Rate Coefficient
A pulsed laser photolysis technique has been employed to investigate the kinetics of the radical-radical reaction O((sup 3)P) + HO2 OH + O2 over the temperature range 266-391 K in 80 Torr of N2 diluent gas. O((sup 3)P) was produced by 248.5-nm KrF laser photolysis of O3 followed by rapid quenching of O(1D) to O((sup 3)P) while HO2 was produced by simultaneous photolysis of H2O2 to create OH radicals which, in turn, reacted with H2O2 to yield HO2. The O((sup 3)P) temporal profile was monitored by using time-resolved resonance fluorescence spectroscopy. The HO2 concentration was calculated based on experimentally measured parameters. The following Arrhenius expression describes our experimental results: k(sub 1)(T) equals (2.91 +/- 0.70) x 10(exp -11) exp[(228 +/- 75)/T] where the errors are 2 sigma and represent precision only. The absolute uncertainty in k, at any temperature within the range 266-391 K is estimated to be +/- 22 percent. Our results are in excellent agreement with a discharge flow study of the temperature dependence of k(sub 1) in 1 Torr of He diluent reported by Keyser, and significantly reduce the uncertainty in the rate of this important stratospheric reaction at subambient temperatures.
Nicovich, J. M.↗
Rotational Relaxation Analysis of Nitrogen in Low-Density Freejet Expansions
The phenomena of rotational relaxation of nitrogen has been examined by numerous investigators over many years. One of the experiments which has been performed examines nonequilibrium flow in low-density free jet expansions. Data have been taken in such flows using a variety of techniques, including time-of-flight methods and electron beam fluorescence spectroscopy. The direct flow properties measured in these different investigations, such as density and translational, rotational and vibrational temperatures generally show reasonable agreement. However, this kind of correlation from experiment to experiment tends to be lost when these data are analyzed to obtain rotational relaxation time or collision number. The goal of such data analyses is to generate a succinct model for rotational relaxation in nitrogen which is essential for the computation of nonequilibrium rarefied flows. The objective of the present work is to process a large body of experimental data in a consistent manner to yield relaxation model parameters of the greatest utility for flow computations.
Gochberg, Lawrence A.↗
Illuminating Cell Biology
NASA's Ames Research Center awarded Ciencia, Inc., a Small Business Innovation Research contract to develop the Cell Fluorescence Analysis System (CFAS) to address the size, mass, and power constraints of using fluorescence spectroscopy in the International Space Station's Life Science Research Facility. The system will play an important role in studying biological specimen's long-term adaptation to microgravity. Commercial applications for the technology include diverse markets such as food safety, in situ environmental monitoring, online process analysis, genomics and DNA chips, and non-invasive diagnostics. Ciencia has already sold the system to the private sector for biosensor applications.
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