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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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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

High dispersion spectroscopic studies of Mars. V - A search for oxygen in the atmosphere of Mars.

In order to set a new upper limit on the amount of diatomic oxygen in the atmosphere of Mars, we have reduced a number of high-dispersion spectra of the 7620 A band of oxygen obtained during the 1969 apparition of Mars. Our new upper limit is 15 atm cm(stp) for the Martian abundance in a single vertical path. This result confirms and lowers the 1963 upper limit of 70 cm atm(stp) by Kaplan, Muench, and Spinrad (1964). The features reported by Hunten and Belton (1966) do not appear on our spectra. Further, we have measured the pressure shift of the A band in the laboratory, and found that the shift required by their tentative identification of diatomic oxygen in the Martian atmosphere does not exist. We conclude that their tentative identification was spurious, and their upper limit dubious.

Margolis, J. S.↗
NASA NTRS1972

Laser-induced gas breakdown - Spectroscopic and chemical studies.

Discussion of the results of several experimental investigations on laser-induced gas breakdown. The experiments included time-resolved spectroscopy, direct detection of H atoms with a TiO2 probe, and chemical reactions; each of them provided insight into the behavior of the medium at different times. Chemical reactions and explosions have been initiated by the laser beam when a plasma was created. No primary multiphotonic absorption and no macroscopic chemical reactions were observed below the breakdown threshold.

De Montgolfier, PH.↗
NASA NTRS1972

Composition of the Venus cloud tops in light of recent spectroscopic data.

The observed chemical composition of the atmosphere near the Venus cloud tops, the refractive index of cloud particles as deduced from polarization data, and the 3-4-micron reflectivity of the clouds are discussed. The data are shown to be consistent with and to strongly support the possibility that the topmost clouds of Venus are composed of concentrated aqueous HCl solutions.

Lewis, J. S.↗
NASA NTRS1972

Spectroscopic observations of comets

The value of C-12/C-13 for the Comets Tago-Sato-Kosaka and Bennett was investigated. The values for both comets are presented in spectrographs.

Owen, T. C.↗
NASA NTRS1973

Mars: Mariner 9 spectroscopic evidence for H2O ice clouds

Spectral features observed with the Mariner 9 Interferometer Spectrometer are identified as those of water ice. Measured spectra are compared with theoretical calulations for the transfer of radiation through clouds of ice particles with variations in size distribution and integrated cloud mass. Comparisons with an observed spectrum from the Tharsis Ridge region indicate water ice clouds composed of particles with mean radius 2.0 microns and integrated cloud mass 0.00005 g/sq cm.

Curran, R. J.↗
NASA NTRS1973

A spectroscopic study of CW chemical lasers.

A subsonic transverse-flow chemical laser has been instrumented to permit measurements of vibration-rotation state populations and laser output spectra under flow conditions typical of present CW hydrogen halide laser operation. Measurements are presented for the F + HI, F + HBr, F + CH4, F + HCl, F + H2, Cl + HI, and Cl + HBr atom-exchange reaction systems. CW operation was found to be characterized by relatively modest departures from Maxwell-Boltzmann vibrational energy distributions at all stages of reaction in contrast to pulsed operation based on similar reactions.

Rosen, D. I.↗
NASA NTRS1973

Spectroscopic observations of the Cygnus X-1 optical candidate.

Data from nine high-dispersion spectra of HDE 226868, the optical candidate for Cyg X-1, are presented. The line profiles at He II (4686 A) show marked changes from night to night. Our data are not compatible with models where the emission line arises from the unseen secondary component of the system, as has been suggested by other observers. We propose that the emission originates in a gas stream falling toward the secondary; this provides observational evidence that the X-ray source is powered by accretion. We also see changes in spectral type and luminosity class with phase, further complicating attempts to make mass estimates for the system.

Smith, H. E.↗
NASA NTRS1973

Moessbauer spectroscopic studies of iron-doped rutile.

Moessbauer spectra were obtained of single crystal and powdered samples of rutile (TiO2) doped to about one percent by weight in isotopically enriched iron. It is shown that the oxidation state may be reversibly altered in situ. After reduction, the oxygen neighbors of the dopant ion are apparently shifted to accomodate the larger ferrous ion. The agreement of calculated quadrupole splittings with experimental results suggests that impurities and oxygen vacancies are uniformly distributed in powdered samples, giving the dopant ions an 'ideal lattice' local environment. The differences between the single crystal and powder sample hyperfine parameters are attributed to variations in stoichiometry, charge compensation mechanisms, or other diffusion related parameters.

Stampfl, P. P.↗
NASA NTRS1973

Does spectroscopic evidence require two scattering layers in the Venus atmosphere.

Comments on Hunt's (1972) conclusion that the phase variation of lines in the 7820- and 7883-A CO2 bands is due to the presence of two scattering layers in the Venusian atmosphere. It is shown that the increase of equivalent width with phase between 0 and 90 deg noted by Hunt in the data by Gray Young et al. (1971) does not necessarily require a two-layer model of scattering in the Venusian atmosphere and that this increase may be due to the strong backward lobe in the Venusian cloud phase function. Hunt, in a reply, notes that Regas et al. incorrectly use in their analysis Hansen's (1969) data which are for a homogeneous planetary atmosphere, while Hunt used an inhomogeneous model of the Venusian atmosphere. In addition, further evidence to support Hunt's claim for a multilayered structure of the upper Venusian clouds is presented.

Regas, J. L.↗
NASA NTRS1973

High altitude infrared spectroscopic evidence for bound water on Mars.

The reflectivity of the Martian surface has been measured between 2.0 and 4.0 microns. A broad absorption band is observed which has a minimum at 2.85 microns. The position and shape of the band is compared to features in numerous terrestrial minerals. Bound water in the Martian surface material is the most likely cause of the observed band. The strength of the observed band suggests a bound water content of approximately 1% by weight. The band is inconsistent with more than a few % limonite or hydrated polymeric carbon suboxide. A mean particle radius of about 100 microns is deduced. The quality of bound water derived has a range of geological, climatic, and exobiological implications.

Houck, J. R.↗