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NASA NTRS1984

Submillimeter, millimeter, and microwave spectral line catalogue

This report describes a computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10000 GHz (i.e., wavelengths longer than 30 micrometers). The catalogue can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue has been constructed using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (151 species) as new data appear. The catalogue is available from the authors as a magnetic tape recorded in card images and as a set of microfiche records.

Poynter, R. L.↗

NASA NTRS1982

Airborne far-infrared and submillimeter spectroscopy

This paper is a review of airborne spectroscopic observations in the wavelength range 18-800 microns, and the instruments on the NASA Kuiper Airborne Observatory with which they were carried out. Recent measurements of spectral lines of ions, atoms and molecules are presented and discussed.

Watson, D. M.↗

NASA NTRS1984

Basic governing equations for the flight regimes of aeroassisted orbital transfer vehicles

The basic governing equations for the low-density, high-enthalpy flow regimes expected in the shock layers over the heat shields of the proposed aeroassisted orbital transfer vehicles are derived by combining and extending existing theories. The conservation equations are derived from gas kinetic principles for a four-component ionized gas consisting of neutral molecules, neutral atoms, singly ionized ions, and electrons, assuming a continuum flow. The differences among translational-rotational, vibrational, and electron temperatures are accounted for, as well as chemical nonequilibrium and electric-charge separation. Expressions for convective and viscous fluxes, transport properties, and the terms representing interactions among various energy modes are given explicitly. The expressions for the rate of electron-vibration energy transfer, which violates the Landau-Teller conditions, is derived by solving the system of master equations accounting for the multiple-level transitions.

Lee, J.-H.↗

NASA NTRS1985

Understanding the high pressure properties of molecular solids and molecular surfaces deposited on hetrogeneous substrates

Work directed toward understanding the high pressure properties of molecular solids and molecular surfaces deposited on hetrogeneous substrates is reported. The motivation, apart from expanding our basic knowledge about these systems, was to understand and predict the properties of new materials synthesized at high pressure, including pressure induced metallic and superconducting states. As a consequence, information about the states of matter of the Jovian planets and their satellites, which are natural high pressure laboratories was also provided. The work on molecular surfaces and finite two and three dimensional clusters of atoms and molecules was connected with the composition and behavior of planetary atmospheres and on the processes involved in forming surface layers, which is vital to the development of composite materials and microcircuitry.

Etters, R. D.↗

NASA NTRS1985

Interaction of the Magnetospheric Ions with the Surfaces of the Icy Satellites of Saturn

The extraordinary connection between the compositions of the surfaces of the satellites and ring particles and the composition of the magnetospheric plasmas in which they are embedded is examined. What may be even more exciting is this connection is being developed and understood via a combination of laboratory and satellite measurements. This interaction has stimulated new research on radiation effects in materials which will be technologically useful. Laboratory measurements have begun to characterize the changes induced in ice by ion and electron bombardment. Most attention was paid to measurements of the atoms and molecules ejected via ion bombardment, but work was initiated on changes in the spectral character of the ice. Recent results on CH4 and mixtures of HZO and CH4 indicate that a considerable amount of chemistry is induced in such ices via bombardment.

Johnson, R. E.↗

NASA NTRS1985

Computational chemistry and aeroassisted orbital transfer vehicles

An analysis of the radiative heating phenomena encountered during a typical aeroassisted orbital transfer vehicle (AOTV) trajectory was made to determine the potential impact of computational chemistry on AOTV design technology. Both equilibrium and nonequilibrium radiation mechanisms were considered. This analysis showed that computational chemistry can be used to predict (1) radiative intensity factors and spectroscopic data; (2) the excitation rates of both atoms and molecules; (3) high-temperature reaction rate constants for metathesis and charge exchange reactions; (4) particle ionization and neutralization rates and cross sections; and (5) spectral line widths.

Cooper, D. M.↗

NASA NTRS1984

Measuring spectra of arid lands

The principles, instrumentation and data acquisition and interpretation techniques employed in multispectral remote sensing for geological applications are surveyed. Sensing is based on exact measurements of electromagnetic radiation interacting with atoms and molecules in the sensed scene. Absorbed radiation can be used to identify elements in the near-IR bands and emitted or reflected energy can be sensed in the mid- and far-IR. Sunlight normally serves as the exciting source. Wavelength absorptance and emittance characteristics are distinct for the various elements and molecules such as transition metal ions, water, carbonates, etc. The bands for identifying different materials are determined in the laboratory, followed by ground truth field tests. Several hand-held radiometers and spectrometers have been developed for the field trials. Each instrument usually has a limited detection range and serves for developing a data base for subtle distinctions among contiguous minerals with similar radiometric signatures. The data serve for calibrating first airborne and then satellite sensors, e.g., the Landsat MSS and Thematic Mapper. Instruments are also being tested using the Orbiter as the test platform.

Kahle, A. B.↗

NASA NTRS1985

Chemistry in dynamically evolving clouds

A unified model of chemical and dynamical evolution of isolated, initially diffuse and quiescent interstellar clouds is presented. The model uses a semiempirically derived dependence of the observed cloud temperatures on the visual extinction and density. Even low-mass, low-density, diffuse clouds can collapse in this model, because the inward pressure gradient force assists gravitational contraction. In contrast, previous isothermal collapse models required the low-mass diffuse clouds to be unrealistically cold before gravitational contraction could start. Theoretically predicted dependences of the column densities of various atoms and molecules, such as C and CO, on visual extinction in diffuse clouds are in accord with observations. Similarly, the predicted dependences of the fractional abundances of various chemical species (e.g., CO, H2CO, HCN, HCO(+)) on the total hydrogen density in the core of the dense clouds also agree with observations reported to date in the literature. Compared with previous models of interstellar chemistry, the present model has the potential to explain the wide spectrum of chemical and physical properties of both diffuse and dense clouds with a common formalism employing only a few simple initial conditions.

Tarafdar, S. P.↗

NASA NTRS1985

Submillimeter, millimeter, and microwave spectral line catalog

Poynter, R. L.↗

NASA NTRS1986

Carbon Shields for Intercalated Fiber Conductors

Stability in air increased by depositing amorphous carbon. Initially graphite fibers intercalated (insertion of atoms or molecules between graphite layers). Next, conductor coated with diamondlike amorphous carbon. Coating applied in same chamber as intercalation reaction or alternate deposichamber is used. Deposition of carbon accomplished by any number of techniques. tion Ion-beam sputter-deposition and RF plasma techniques have been used, but dc plasma and others work also. Potential uses include conductive epoxy composites, tether conductors, signal wire, and power cables.

Banks, B. A.↗

NASA NTRS1985

Diffusion and solubility of oxygen in silver

The diffusion and solubility of oxygen in Ag in the temperature range between 412 and 862 C was determined. The following interpolation formula was found for the solubility: L = 8.19.1/100.exp(-11 860/RT)Mol O2/g.At.Ag.at 1/.5. The process obeys the Sieverts square root law within the limits of error. The dissolution of oxygen in Ag may be accompanied by the dissociation of the oxygen molecules into atoms. The tests on Ag-foils reveal that below a temperature of about 500 C a higher solubility is simulated by the adsorption of oxygen. The diffusion coefficient of oxygen in silver obeys the following equation: D = 2.72.1/100.exp(-11 000/RT)sq cm/s. The relatively low activation energy of 11 kcal/g.At suggests that the diffusion of oxygen takes places over interstitial sites.

Eichenauer, W.↗

NASA NTRS1986

Measurement of partial pressures in vacuum technology and vacuum physics

It is pointed out that the measurement of gaseous pressures of less than 0.0001 torr is based on the ionization of gas atoms and molecules due to collisions with electrons. The particle density is determined in place of the pressure. The ionization cross sections for molecules of various gases are discussed. It is found that the true pressure in a vacuum system cannot be determined with certainty if it is unknown which gas is present. Effects of partial pressure determination on the condition of the vacuum system are discussed together with ion sources, systems of separation, and ion detection.

Huber, W. K.↗

NASA NTRS1985

Laser radar observation of the polar stratospheric aerosol layer

The polar stratosphere has been speculated to be an active sink region of various stratospheric materials; ozone, water vapor, NOX, aerosol particles and so on, but this process is not theoretically and/or observationally made clear. The observation of the polar stratospheric aerosol layer using laser radar certainly contributes to the study of the global transport of these stratospheric minor constituents. In addition to this, from the viewpoint of aerosol science, there may be many interesting phenomena which cannot be found in the stratosphere at mid and low latitudes; the effect of precipitation of high energy molecules and atoms, of very cold winter stratosphere, of very cold mesopause in summer. Laser radar observation is one of the main activities of the Antarctic Middle Atmosphere (AMA) project at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica since May 1983. Laser radar measurement at Syowa Station is discussed in detail.

Iwasaka, Y.↗

NASA NTRS1985

Theoretical research program to study transition metal trimers and embedded clusters

Small transition metal clusters at a high level of approximation i.e. including all the valence electrons in the calculation and also including extensive electron correlation were studied. Perhaps the most useful end result of these studies is the qualitative information about the electronic structure of these small metal clusters, including the nature of the bonding. The electronic structure studies of the small clusters are directly applicable to problems in catalysis. From comparison of dimers, trimers and possibly higher clusters, it is possible to extrapolate the information obtained to provide insights into the electronic structure of bulk transition metals and their interaction with other atoms and molecules at both surface and interior locations.

Walch, S. P.↗

NASA NTRS1985

An airborne lidar instrument for detection of OH using the technique of laser-induced fluorescence

Under suitable laboratory conditions, it has been demonstrated that the laser-induced fluorescence (LIF) measurement technique is sensitive enough to detect single atoms and molecules. This potential sensitivity has provided motivation for the development of this technique for ambient OH measurements. The present paper is concerned with an airborne lidar instrument for measuring OH concentration as used for the NASA GTE/CITE (Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation) intercomparison experiments during the fall of 1983 and the spring of 1984. A description is given of a working airborne instrument for measurements of OH in ambient air. The detection sensitivity demonstrated in the experiments should be sufficient for routine measurements in areas in which the OH concentration is in the range of high 1,000,000 molecule per cu cm or higher.

Davis, L. I., Jr.↗

NASA NTRS1986

Low-energy electron-atom bremsstrahlung

This paper extends recent work providing an elementary calculation of bremsstrahlung and opacity associated with the scattering of low-energy electrons by neutral atoms and molecules. The method applies when the scattering potential is 'hard' or when the collision time is short, applying the classical soft-photon emission probability formula for arbitrary bremsstrahlung photon energy. However, now, in addition to correcting the probability factor for finite bremsstrahlung photon energy, another factor corrects for the reduced phase space available to the outgoing electron. The bremsstrahlung cross section and opacity are then computed directly from the elastic scattering cross section, determined experimentally or calculated; a small (approximately 10 percent) correction is computed from the anisotropic term in the elastic scattering cross section. The opacity is evaluated for electron scattering by H, He, and H2 using experimentally determined values for the elastic scattering cross section, and is compared with more elaborate calculations. The agreement is good (within 10 percent), indicating an accuracy for the general method comparable to variations among the results of different elaborate theoretical computations. The agreement seems to validate the basic approximation of short collision time even at large bremsstrahlung photon energy for electron energies and temperatures up to a few eV.

Gould, R. J.↗

NASA NTRS1986

Spacecraft mass spectrometer ion source employing field emission cathodes

An ion source that utilizes a pair of thin-film field emission cathodes to provide current for electric impact ionization is studied. The field emission cathodes are composed of microscopically small needle tips and an extraction electrode; the cathodes generate a 200-eV, 0.1-mA electron beam. The multistep process for the manufacturing of the field emission cathodes is examined. The operation of the ion source, which ionizes atoms and molecules that enter the mass spectrometer with a ram velocity of about 80 km/sec, is described.

Curtis, C. C.↗

NASA NTRS1986

Detection of surface glow related to spacecraft glow phenomena

A source of low energy neutral atoms and molecules has been developed by using a biased limiter to scrape off and reflect neutralized ions from a toroidal plasma. Beams of nitrogen and nitrogen-oxygen mixtures with energies of 1 to 15 eV and fluxes greater than about 10 to the 14 per centimeter per second were directed onto target surfaces consisting of Z-302 and Z-306 paints. With the nitrogen beams, a glow due to beam-surface interactions was successfully detected. In addition, a volume glow effect due to beam-gas interactions was observed which may play a role in spacecraft glow.

Langer, W. D.↗