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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Differential elastic scattering cross section of Ar nozzle beam in nitrogen considered with rainbow effect in determining intermolecular potential well depth
Scattering cross sections for monoenergetic Ar beams on epitaxial Ag films
Comparison of generalized phase shift treatment with classical trajectory calculations of rotational inelasticity cross sections of Ar-N2 scattering
Ne, Ar, Kr and Xe ionized states transition and level lifetimes from photographically recorded beam foil spectra, discussing particle energies
Vibration effects on image resolution and acutance of Zeiss RMK AR 15/23 aerial camera, using aircraft vibration simulator for testing
Molecular rotational excitation during CO ion-Ar interactions by ion beam collision spectroscopy, observing energy loss spectra
Apollo 14 Fra Mauro rock fragment samples, determining Ar 40/Ar 39 ages
Transition probabilities for Ar I, using Coulomb approximation values of radial wave function integral
Data reduction procedures for determining free-stream and post-normal-shock flow conditions are presented. These procedures are applicable to flows of CO2, N2, O2, Ar, or mixtures of these gases and include the effects of dissociation and ionization. The assumption of thermochemical equilibrium free-stream and post-normal-shock flow is made. Although derived primarily to meet the immediate needs of an expansion tube of a hot gas radiation research facility, these procedures are applicable to any supersonic or hypersonic test facility using these gases or mixtures thereof. The data reduction procedures are based on combinations of three of the following flow parameters measured in the immediate vicinity of the test section: (1) stagnation pressure behind normal shock, (2) free-stream static pressure, (3) stagnation-point heat-transfer rate, (4) free-stream velocity, and (5) free-stream density. Thus, these procedures do not depend explicitly upon measured or calculated upstream flow parameters. The procedures are incorporated into a single computer program written in FORTRAN IV language. A listing of this computer program is presented, along with a description of the inputs required and a sample of the data printout.
The reaction sequence leading from O2(+) to H3O(+)-H2O was examined in He, Ar, N2 and O2 carrier gases in a flowing afterglow system. The rate constants for the reactions were measured and the kinetic analysis for their determination is presented. For M = N2, two new steps involving the formation and reaction of O2(+)-N2 were proposed and examined. The rate constants are discussed and compared with other experimental values.
Determination of physisorption isotherms of these gases on stainless steel by pressure change measurements in very low pressure cryogenic baths where a steel nipple was brought in contact with the test gas at 77 to 90 K in a sealed constant-volume system. The position of the nipple in the gas was changed in such a manner that gas adsorption on a 47.5 sq cm area of the steel surface could be measured. The Dubinin-Radushkevich (DR) equation (1947) was used for an empirical description of isotherms at different temperatures. The mean adsorption energies calculated from the DR plots were 1290, 1545, 1490 and 1903 cal/mol for Ar, Kr, CH4 and N2, respectively, being about 10% higher than the corresponding values on Pyrex.
Determination of collisional-excitation-rate coefficients for sodium-like Ar VIII ions theoretically using the Coulomb-Born approximation as well as experimentally from the absolute intensities of lines emitted by these ions in well-diagnosed plasmas whose parameters were obtained from the analysis of scattered laser light. These plasmas were produced in a theta-pinch device. The agreement between theory and experiment is within the estimated accuracy of plus or minus 50% for excitation from the ground state to the n = 3 and n = 4 levels, whereas some deviations are observed for two transitions to the n = 5 levels at lower temperatures. A rate coefficient for ionization was obtained from the time dependence of the ionization.
Beams of O(+) and Ar(+) in the energy range from 100 to 300 eV were directed into an aperture in one face of a copper box. The mass spectrum from a similar aperture in an adjacent face was observed with the aid of a commercial RF quadrupole spectrometer. On the basis of the results obtained it is reported that O(+) beams at about 200 eV may be essentially lost after a few collisions with a surface, in agreement with similar conclusions about atomic oxygen at thermal energies.
To test the accuracy of the Gordon-Kim theory of intermolecular forces, predicted and experimental values are compared for Ar-HCl. The method appears to accurately predict the short-range repulsive forces and also the position (but possibly not the depth) of the potential well.
The sorption of argon, carbon dioxide, and nitrogen on two heat shield composites (SLA-561 and SLA-561V) and on the SLA components was measured over the pressure range of 0.001 to 760 torr and in the temperature range of 30 to 50 C. The sorption of the gases by both the composites and the components varied directly with pressure. The sorption of CO2 by the phenolic spheres and the silicone elastomer and of Ar by the silicone elastomer varied inversely with temperature. The mechanism involved in the gas sorption was primarily absorption.
The relative importance of two primary processes in the photolyis of water: (1) H2O + h (nu) yields H + OH, and (2) H2O + h (nu) yields H2 + OD-1 were determined in a direct manner by time resolved detection (via resonance fluorescence) of H and O formed in processes 1 and 2 respectively. The initially formed OD-1 was deactivated to ground state OP-3 prior to detection via resonance fluorescence. The relative quantum yields for processes 1 and 2 are 0.89 and 0.11 for the wavelength interval 105 to 145nm and = to or greater than 0.99, and = to or less than 0.01 for the wavelength interval 145 to 185nm. Rate constants at 300 K for the reactions OD-1 + H2, + Ar, and + He are presented.
The technique employed in the study utilizes the vacuum ultraviolet flash photolysis of H2O combined with time resolved, simultaneous detection of H and O via resonance fluorescence at 121.6 and 130.2 nm respectively. The measurements were made by means of photon counting and multichannel scaling. The sensitivity of the system for H and O is discussed. Experiments are reported in which signals due to H and O were accumulated from the flash photolysis of a mixture of 0.1 torr H2O and 100 torr Ar. Attention is given to the relative importance of two primary processes in the photolysis of water.
Results of argon dating of lunar breccias from Apollo 14, 15, and 16 samples are presented. Basic chronological information was obtained on samples of 14270, 15362, 15455, and 63335,3; these samples averaged about 4 billion years in age. 14301 and 14313 were never isotopically homogenized and therefore do not yield ages. However, trapped argon in these breccias consists of two components, with one component rich in Ar-40 and fractionating at low temperatures during stepwise heating experiments.