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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

A flash photolysis-resonance fluorescence study of the formation of O(D-1) in the photolysis of water and reaction of O(D-1) with H2, Ar and He

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.

Stief, L. J.↗
NASA NTRS1976

Light flash observations during Apollo-Soyuz

A total of 82 visual events was reported by two dark-adapted astronauts during a 90-minute orbit at 225 km altitude. Silver chloride crystal events for that orbit totaled 69 stopping protons and alphas per sq cm and 304 heavy ions with stopping power of 150 MeV sq cm/g or greater. The frequency of visual observations near the geomagnetic poles corresponds to calculated abundances of ions with LET greater than 5 keV per micrometer in tissue. Nuclear collisions of fast protons on C, N, and O in the retina or the abundance of stopping protons can explain the low frequency of events in the SAA for this mission in comparison with the high frequency during Skylab IV at 443 km altitude.

Budinger, T. F.↗
NASA NTRS1977

The possibility of flash fires in toxicity tests

The concentrations of combustible compounds in the gases generated in toxicity tests may together result in a flammable mixture which could be ignited by accident or by a deficiency in procedure. The principal hazard stems from the increase in the concentrations of combustible non-toxic gases which may result from efforts to increase the concentrations of toxic gases to obtain desired physiological responses.

Hilado, C. J.↗
NASA NTRS1977

A quantum yield determination of O/1D/ production from ozone via laser flash photolysis

The quantum yield of electronically excited atomic oxygen produced from ozone photolysis was measured at 298 K from wavelengths of 293.0 to 316.5 nm. The reaction of the atomic oxygen with N2O to form excited NO2 was used to monitor the O production; a frequency-doubled flashlamp-pumped dye laser which provided tunable ultraviolet in the desired spectral region with 0.1-nm linewidth served as the photolysis source. The atomic oxygen quantum yield was found to be constant below 300 nm, with a sharp decrease centered at 308 nm and a diminution to less than one tenth of the constant value by 313.5 nm.

Philen, D. L.↗
NASA NTRS1979

Deep radio occultations and 'evolute flashes' - Their characteristics and utility for planetary studies

Deep radio occultation signals from spacecraft passing behind planets may provide data on atmospheric absorption, turbulence, and structure, as well as information on the effects of planetary gravitational moments, rotation and zonal winds on the atmospheric shape. The strength of radio signals from a spacecraft passing behind a planet will at first decrease because of defocusing in the atmosphere, but then increase as the evolute of the planetary limb is neared, due to focusing caused by limb curvature within the evolute. Within the evolute, the availability of four simultaneous signal paths over four limb positions may render focused signals instantaneously great. The passage of Voyager 1 behind Jupiter and Voyager 2 behind Saturn will provide a test of deep radio occultation studies.

Eshleman, V. R.↗
NASA NTRS1980

Laser flash photolysis of ozone - O/1D/ quantum yields in the fall-off region 297-325 nm

The wavelength dependence of the quantum yield for O(1D) production from ozone photolysis has been determined between 297.5 nm and 325 nm in order to resolve serious discrepancies among previous studies. The results of this investigation are compared to earlier work by calculating atmospheric production rate constants for O(1D). It is found that for the purpose of calculating this rate constant, there is now good agreement among three studies at 298 K. Furthermore, it appears that previous data on the temperature dependence of the O(1D) quantum yield fall-off is adequate for determining the vertical profile of the O(1D) production rate constant. Several experimental difficulties associated with using NO2(asterisk) chemiluminescence to monitor O(1D) have been identified.

Brock, J. C.↗
NASA NTRS1982

Picosecond flash spectroscopic studies on ultraviolet stabilizers and stabilized polymers

Spectroscopic and excited state decay kinetics are reported for monomeric and polymeric forms of ultraviolet stabilizers in the 2-(2'-hydroxyphenyl)-benzotriazole and 2-hydroxybenzophenone classes. For some of these molecules in various solvents at room temperature, (1) ground state absorption spectra, (2) emission spectra, (3) picosecond time-resolved transient absorption spectra, (4) ground state absorption recovery kinetics, (5) emission kinetics, and (6) transient absorption kinetics are reported. In the solid state at low temperatures, emission spectra and their temperature dependent kinetics up to approximately 200K as well as, in one case, the 12K excitation spectra of the observed dual emission are also reported.

Scott, G. W.↗
NASA NTRS1982

Development of a flash, bang, and smoke simulation of a shell burst

A large number of experiments (cue test firings) were performed in the definition of the cue concepts and packaging configurations. A total of 344 of these experiments were recorded with instrumentation photography to allow a quantitative analysis of the smoke cloud to be made as a function of time. These analyses were predominantly made using a short test site. Supplementary long range visibility tests were conducted to insure the required 3 kilometer visibility of the smoke signature.

Williamson, F. R.↗
NASA NTRS1981

A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

Wine, P. H.↗
NASA NTRS1981

Visible and infrared techniques for flash flood, hydrological, and agricultural applications

A common requirement of these agriculture, climatology and hydrology fields is the accurate and timely estimation of precipitation. Yet, it is often difficult to obtain such estimates by conventional means. The advent of satellite remote sensing however has opened the possibility of making rain estimates over time and space scale never before available. A computer automated technique that estimates a summertime convective rainfall from the thermal infrared imagery of geosynchronous satellites is reviewed.

Scofield, R. A.↗