Search NASA⌕ Search

SEARCH · Search NASA

Results for “Absorption”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Absorption of sound in air - High-frequency measurements

The absorption of sound in air at frequencies from 4 to 100 kHz in 1/12 octave intervals, for temperatures from 255.4 K (0 F) to 310.9 K (100 F) in 5.5 K (10 F) intervals, and at 10% relative-humidity increments between 0% and saturation has been measured. The values of free-field absorption have been analyzed to determine the relaxation frequency of oxygen for each of the 92 combinations of temperature and relative humidity studied and the results are compared to an empirical expression. The relaxation frequencies of oxygen have been analyzed to determine the microscopic energy-transfer rates.

Bass, H. E.↗
NASA NTRS1977

High resolution absorption cross sections for the A2Pi-X2Pi system of ClO

High-resolution ultraviolet absorption cross-sections for the ClO molecule are obtained, with the aim of facilitating studies of ozone depletion resulting from the injection of chlorofluorocarbons into the atmosphere. The spectroscopic analysis, which involves a frequency-doubled tunable dye laser with a bandwidth of 0.015 A, is described. Studies of the rotational lines of the ClO A 2Pi 3/2-X2Pi 3/2 9-10 band were conducted. Peak cross-sections for the P and R lines of the 9-0 band are found to be 10.0, 9.6, 8.6, 10.6, 10.3, and 9.2 times ten to the negative seventeenth power cm squared, with estimated accuracy of plus or minus 25%. Problems in distinguishing between Cl-35 and Cl-37 absorption are also considered.

Wine, P. H.↗
NASA NTRS1976

Measured performance of a 3-ton LiBr absorption water chiller and its effect on cooling system operation

A 3-ton lithium bromide absorption water chiller was tested for a number of conditions involving hot-water input, chilled water, and the cooling water. The primary influences on chiller capacity were the hot water inlet temperature and the cooling water inlet temperature. One combination of these two parameters extended the output to as much as 125% of design capacity, but no combination could lower the capacity to below 60% of design. A cooling system was conceptually designed so that it could provide several modes of operation. Such flexibility is needed for any solar cooling system to be able to accommodate the varying solar energy collection and the varying building demand. It is concluded that a 3-ton absorption water chiller with the kind of performance that was measured can be incorporated into a cooling system such as that proposed, to provide efficient cooling over the specified ranges of operating conditions.

Namkoong, D.↗
NASA NTRS1978

The economics of solar powered absorption cooling

Analytic procedure evaluates cost of combining absorption-cycle chiller with solar-energy system in residential or commercial application. Procedure assumes that solar-energy system already exists to heat building and that cooling system must be added. Decision is whether to cool building with conventional vapor-compression-cycle chiller or to use solar-energy system to provide heat input to absorption chiller.

Bartlett, J. C.↗
NASA NTRS1977

Atlas of Infrared Absorption Lines

This atlas of infrared absorption line contains absorption line parameters (line strength vs. wavenumber) from 500 to 7000 cm(exp-1) for 15 gases: H2O, CO2, O3, N2O, CO, CH4, O2, SO2, NO, NO2, NH3, HCl, HF, HNO3 and CH3Cl.

Park, J. H.↗
NASA NTRS1977

Absorption strength measurement of the nu-1 band of methyl chloride

The absorption strengths of the Q-branch manifolds of the nu-1 band of methyl chloride were measured. The results were used to deduce the band strength, which is 32.1 plus or minus 2.9 per sq cm-atm at 297 K. The P-branch absorptions were investigated to assess the possibility of determining a vibration-rotation factor for the band. This factor is approximately 1.026.

Margolis, J. S.↗
NASA NTRS1977

Ultraviolet absorption spectrum of hydrogen peroxide vapor

The ultraviolet absorption cross sections of hydrogen peroxide vapor have been determined over the wavelength range 210 to 350 nm at 296 K. At the longer wavelengths, the gas phase absorptivities are significantly larger than the corresponding values in condensed phase. The atmospheric H2O2 photodissociation rate for overhead sun at the earth's surface is estimated to be about 1.3 x 10 to the -5th/sec.

Molina, L. T.↗
NASA NTRS1978

A comparison of neutral hydrogen 21 cm observations with UV and optical absorption-line measurements

Several absorption components detected in visible or UV lines have been identified with emission features in new high-resolution, high signal-to-noise 21 cm observations. Stars for which direct overlap is obtained are HD 28497, lambda Ori, mu Col, HD 50896, rho Leo, HD 93521, and HD 219881. With the use of the inferred H I column densities from 21 cm profiles, rather than the integrated column densities obtained from L-alpha, more reliable densities can be derived from the existence of molecular hydrogen. Hence the cloud thicknesses are better determined; and 21 cm emission maps near these stars can be used to obtain dimensions on the plane of the sky. It is now feasible to derive detailed geometries for isolated clumps of gas which produce visual absorption features.

Giovanelli, R.↗
NASA NTRS1978

Ultraviolet absorption cross sections of hydrogen peroxide

Absorption cross-sections of hydrogen peroxide vapor and of neutral aqueous solutions of hydrogen peroxide were measured in the wavelength range from 195 to 350 nm at 296 K. The spectrophotometric procedure is described, and the reported cross-sections are compared with values obtained by other researchers. Photodissociation coefficients of atmospheric H2O2 were calculated for direct absorption of unscattered solar radiation, and the vertical distributions of these coefficients are shown for various solar zenith angles.

Lin, C. L.↗
NASA NTRS1978

On the dissociation of nitrogen by electron impact and by EUV photo-absorption

The dissociation of N2 by electron impact and by absorption of EUV photons was studied experimentally. It was shown that most of the N2 molecules excited to singlet states in the 12.5-14.86 eV range are depopulated by predissociation and not by the emission of EUV photons and that this is the principal mechanism by which N2 is dissociated by solar EUV absorption and by electron impact. The experiments provide a physical explanation for the near absence of N2 band radiation in airglow and auroral EUV spectra, and rule out the excitation of EUV radiation as a major factor in the overall energy economy of an auroral substorm.

Zipf, E. C.↗
NASA NTRS1978

Differential laser absorption monitoring of the atmosphere

In the airborne detection system of atmospheric constituents and pollutants described, double-ended differential absorption measurement is accomplished by rapidly current tuning the wavelength of a PbSSe diode laser across a single line of the species under consideration. As the laser wavelength sweeps periodically across the absorption line, the laser beam is amplitude modulated and is then synchronously detected. With this technique, a minimum detectable differential transmission of 0.02 percent is obtained for a 1-sec integration time.

Rubin, B.↗
NASA NTRS1978

Absorption strength of the perturbed nu-4 band of CH3Cl

The nu-4 band of CH3Cl interacts strongly with the 3 nu-6 band. Levels of both bands are mixed and both appear strongly in absorption. The strengths of both bands have been measured taking into account the mixing of the levels. The absorption strengths of both bands can be related to a single parameter, namely, the strength of the unperturbed nu-4 band. This was calculated to be 41.8 per sq cm/atm at 297 K.

Margolis, J. S.↗
NASA NTRS1979

Low absorptance porcelain-on-aluminum coating

Porcelain thermal-control coating for aluminum sheet and foil has solar absorptance of 0.22. Specially formulated coating absorptance is highly stable, changing only 0.03 after 1,000 hours of exposure to simulated sunlight and can be applied by standard commercial methods.

Leggett, H.↗
NASA NTRS1978

The airborne Laser Absorption Spectrometer - A new instrument of remote measurement of atmospheric trace gases

The Laser Absorption Spectrometer is a portable instrument developed by JPL for remote measurement of trace gases from an aircraft platform. It contains two carbon dioxide lasers, two optical heterodyne receivers, appropriate optics to aim the lasers at the ground and detect the backscattered energy, and signal processing and recording electronics. Operating in the differential-absorption mode, it is possible to monitor one atmospheric gas at a time and record the data in real time. The system can presently measure ozone, ethylene, water vapor, and chlorofluoromethanes with high sensitivity. Airborne measurements were made in early 1977 from the NASA/JPL twin-engine Beechcraft and in May 1977 from the NASA Convair 990 during the ASSESS-II Shuttle Simulation Study. These flights resulted in measurements of ozone concentrations in the lower troposphere which were compared with ground-based values provided by the Air Pollution Control District. This paper describes the details of the instrument and results of the airborne measurements.

Shumate, M. S.↗
NASA NTRS1979

Absorption models for low-frequency variability in compact radio sources

The consequences of the most plausible version of the absorption model for low-frequency variability in compact extragalactic radio sources are considered. The general restrictions placed on such a model are determined, and observational tests are suggested that can be used either to support the model or to discriminate among its various versions. It is shown that low-frequency variability in compact radio sources can be successfully explained by a class of models in which the flux is modulated by changes in free-free optical depth within an intervening ionized medium. Two versions of such a model are distinguished, one involving large changes in optical depth and the other, small changes. It is noted that while absorption effects are capable of causing rapid flux and structural variations at centimetric wavelengths, the models predict detailed behavior that is in direct conflict with observational data.

Marscher, A. P.↗
NASA NTRS1979

On the lack of absorption of 1 keV diffuse X-rays by the Small Magellanic Cloud

The contribution to the diffuse X-ray background near 1 keV cosmic (extragalactic) origin is poorly known. Data from a slow scan across the Small Magellanic Cloud by the Wisconsin soft X-ray experiment on OSO 8 are analyzed to search for absorption of a possible cosmic component to the diffuse flux. No indication of an X-ray shadow near 1 keV is found, setting an upper limit to the intensity of the flux originating beyond the SMC that is inconsistent with a cosmic spectrum of 11 E to the -1.4 photons per (sq cm s sr keV), even allowing for depletion of the absorbing elements in the SMC. Unless emission by the SMC or an upward fluctuation in the galactic or cosmic diffuse flux at the position of the SMC has canceled out the expected absorption, the contribution to the diffuse flux at 1 keV from beyond the SMC must be less than 50% of that expected for an extrapolated E to the -1.4 source spectrum.

Bunner, A. N.↗
NASA NTRS1979

A survey of ultraviolet circumstellar absorption lines in the spectra of early Be and shell stars

Copernicus UV data are used to examine the rich shell absorption spectra between 1120 and 1140 A in 17 Be and shell stars. Previous observations of the program stars are reviewed, the general appearance of the shell spectra between 1120 and 1140 A is described, and the shell spectra are compared with the spectra of four bright B-type supergiants in the same wavelength region. The line strengths are analyzed to determine quantitative shell strengths and shell column densities; the shell line velocities are discussed in the context of different models. It is shown that UV shell lines can exist in stars with no visible-wavelength shell features, that Fe III shell lines dominate the spectra between 1120 and 1140 A in Be and shell stars with circumstellar absorption features, and that the spectra of Be and shell stars in this region strongly resemble those of supergiants of similar effective temperature.

Snow, T. P., Jr.↗