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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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NASA NTRS1975

Low energy neutrons from sun

Arguments are presented in support of an earlier suggestion that low-energy neutrons are likely to be more commonly produced in the solar atmosphere. It appears that protons with an energy not exceeding 100 MeV are more significant, especially those with an energy of about 10 MeV. It is also clear that in addition to the light elements C, N, O, and Ne, due attention should be paid to elements such as Mg, Si, S, Fe, etc., and their isotopes, even if they are not so abundant.-

Ahluwalia, H. S.↗
NASA NTRS1977

The abundance of boron in Vega and Sirius

High-resolution (0.05 A) Copernicus observations of the 1362.46-A B II resonance line in Sirius and Vega are analyzed. In Vega, this line is found to be strong, broad, asymmetric, and blended with another line; it is not observed in Sirius. Angular velocities of 18-20 km/s for Vega and 10 km/s for Sirius are determined. A search for subordinate lines of B II reveals no such features in the Sirius spectrum and the possible weak presence of two unblended lines in that of Vega. The cause of the asymmetry of the B II blend in Vega is investigated, line-profile calculations are performed for Sirius, and the B content of Vega is obtained by means of an LTE synthesis of the B II blend as well as a non-LTE computation of the B II line alone. It is concluded that Sirius is deficient in B relative to Vega by a factor of at least 20. The Be abundances of both stars are also examined in relation to the galactic-cosmic-ray spallation theory for the origin of light elements.

Praderie, F.↗
NASA NTRS1978

Gamma ray astronomy and the origin of the light nuclei

Nuclear reactions induced by the collisions of the protons and alphas of the galactic cosmic ray with heavy nuclei of the interstellar gas are responsible for the continuous production of the light elements lithium, beryllium, and boron in the galaxy. To better than one order of magnitude, the observed ratios of these abundances to hydrogen abundance and the nuclidic abundance ratios between themselves are accounted for by simply considering the effect of fast protons and alphas with a flux and an energy spectrum as observed in galactic cosmic rays, for a period comparable with the life of our galaxy. The role of gamma ray astronomy in solving problems that occur when accurate agreement is sought with increasingly accurate data is discussed.

Reeves, H.↗
NASA NTRS1977

Stratospheric aerosols - Undissolved granules and physical state

The physical state of stratospheric aerosol particles was studied along with the nature of included undissolved granules. It was found that: (1) undissolved granules are present in only a third of the aerosol particles and are not always associated with a slurry matrix, (2) those undissolved particles usually contain only sulfur and sodium or undetectable light elements, (3) all stratospheric aerosols have a similar appearance: a volatile slurry mixture of crystalline-like material in a liquid matrix, and (4) variations in the relative amounts of liquid and crystalline materials at different times cause variations in particle spreading.

Farlow, N. H.↗
NASA NTRS1978

Solar-wind sputtering of the Martian atmosphere

The role of solar-wind sputtering in causing atmospheric mass loss from Mars is discussed. The atmospheric mass loss is studied by analogy to models of sputtering of solid surfaces and by use of empirical data for the lunar surface. Results show that Martian atmospheric mass loss, when integrated over the course of 4 times 10 to the ninth power years, amounts to 3.1 times 10 to the 41st power CO2 molecules. Preferential loss of light elements and isotopes by sputtering is also considered.

Haff, P. K.↗
NASA NTRS1979

Cosmology of a charged universe

The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3-K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe.

Barnes, A.↗
NASA NTRS1978

Measurement of the Li/B abundance ratio above 650 MeV/nucleon

A balloon-borne cosmic-ray telescope containing 4 Cerenkov counters and a neon flash tube hodoscope was flown from Sioux City, Iowa in September 1974. The data have been reanalyzed, using information of flashed tubes to reject events due to proton and He interactions. The new event selection has reduced charge overlap between He and Li to an insignificant level, so that abundance ratios involving Li can now be measured with the instrument. Precise correction factors for events lost by inefficiency of the hodoscope have been derived from flight data; they lead to improved accuracy in measurements of light elements.

Byrnak, B.↗
NASA NTRS1979

Physical characteristics of ionized gaseous nebulae

The high angular resolution and the capability of the space telescope to observe ultraviolet radiation are discussed in relation to investigating planetary nebulae. The physical characteristics of planetary nebulae particulary the abundances of the common light elements, the H2 regions, the angular size, and the surface brightness are reviewed. Differences between supernova remants and planetary nebulae and H2 regions are discussed.

Osterbrock, D. E.↗
NASA NTRS1976

An alpha particle instrument with alpha, proton, and X-ray modes for planetary chemical analyses

The interaction of alpha particles with matter is employed in a compact instrument that could provide rather complete in-situ chemical analyses of surfaces and thin atmospheres of extraterrestrial bodies. The instrument is a miniaturized and improved version of the Surveyor lunar instrument. The backscattering of alpha particles and (alpha, p) reactions provide analytical data on the light elements (carbon-iron). An X-ray mode that detects the photons produced by the alpha sources provides sensitivity and resolution for the chemical elements heavier than about silicon. The X-rays are detected by semiconductor detectors having a resolution between 150 and 250 eV at 5.9 keV. Such an instrument can identify and determine with good accuracy 99 percent of the atoms (except hydrogen) in rocks. For many trace elements, the detecting sensitivity is a few ppm. Auxiliary sources could be used to enhance the sensitivities for elements of special interest. The instrument could probably withstand the acceleration involved in semi-hard landings.

Economou, T. E.↗
NASA NTRS1984

Balloon test project: Cosmic Ray Antimatter Calorimeter (CRAC)

Cosmic ray observations from balloon flights are discussed. The cosmic ray antimatter calorimeter (CRAC) experiment attempts to measure the flux of antimatter in the 200-600 Mev/m energy range and the isotopes of light elements between 600 and 1,000 Mev/m.

Christy, J. C.↗
NASA NTRS1984

Track damage and erosion of insulators by ion-induced electronic processes

Track damage and the associated ejection of atoms and molecules from insulators, which occur as a result of ion-induced electronic excitation, are of interest both in their own right and because of the mechanisms through which the energy in the excited electrons is transformed into atomic motion. In this paper an overview is given of the phenomena that are observed. We show that there is a remarkable similarity between the damage profile along the ion's track in the solid and the yield of ejected atoms at the energy that corresponds to each point on the track. It is also seen that the density of extended defects (or, correspondingly, the ejected particle yield) appears to have a 'universal' form that is weakly dependent on the type of material. In the model presented this is a consequence of the inner-shell ionization of light elements in the solid by the incident ion; the resulting Auger decay produces an intense ionization spike that locally triggers the track formation/erosion process. This model allows the estimation of erosion yields/damage profiles for different ions and materials.

Tombrello, T. A.↗
NASA NTRS1985

Cosmological constraints on the lifetime of massive particles

Particles with masses more than a few MeV, decaying into photons or electrons, can cause destruction by photofission of cosmologically produced light elements. A previous calculation of this effect is corrected and extended, and used to derive maximum lifetimes for massive neutrinos; these range from a few thousand seconds upward, depending on the particle mass. Some approximate expressions are given that enable lifetime limits to be obtained for other particles, with different masses and abundances, such as gravitinos. These limits are generally stronger than previously determined constraints, such as distortion of the microwave background by energetic photons.

Lindley, D.↗
NASA NTRS1985

Ion microprobe isotopic measurements of individual interplanetary dust particles

The results of the first extended ion probe study of interplanetary dust particles (IDPs) are reported. The analytic procedures and the current limits on the precision and accurary of isotopic measurements of light elements are discussed in considerable detail. It is shown that isotopic measurements of several elements can be made on different individual fragments of a single IDP of 10-15 microns in size. The deuterium enrichments observed in several of the particles are shown to be intrinsic, providing independent proof that the particles are extraterrestrial. Carbon isotopic measurements on fragments of three IDPs give ratios similar to terrestrial values and show a largely uniform isotopic composition for a given particle. Small, but significant, differences in delta C-13 of about 40 percent between particles are seen.

Mckeegan, K. D.↗
NASA NTRS1986

High resolution CCD spectra of stars in globular clusters. Part 2: Metals and CNO in M71

Palomar coude CCD spectra of resolution 0.3 and 0.6 has been used to redetermine abundances in five stars of the relatively metal rich globular cluster M71. The (Fe/H) value is restricted to the limits of -0.6 to -1.0. The largest source of uncertainty is a systematic difference in f-values between those derived via the Holweger-Muller (1974) solar model and the Bell et al. (1976) solar model. If we use absolute f-values measured by the Oxford group (Blackwell et al. 1982) we find Fe/H to lie in the range of -0.6 to -0.75, i.e., as given by using the Bell et al. solar model. The relative abundances of the light elements, i.e., Na through Ca and probably including Ti show an average excess relative to iron of 0.4 dex. The effect of this difference on metal indices derived from broad- and narrow- band photometry is discussed. For three stars we find O/H = -0.6 using absolute f-values. For CN an analysis of individual rotational lines of the 2-0 band of the red system yields lines in the (C/H,N/H) plane that are consistent with either an original C/Fe = N/Fe = 0 or a modest increase in N relative to C due to CN burning and mixing. A search for C-13N was not successful and an uncertain lower limit of C-12/C-13 near 10 was obtained.

Leep, E. M.↗
NASA NTRS1987

High-resolution CCD spectra of stars in globular clusters. II - Metals and CNO in M71

Palomar coude CCD spectra of resolution 0.3 and 0.6 has been used to redetermine abundances in five stars of the relatively metal rich globular cluster M71. The (Fe/H) value is restricted to the limits of -0.6 to -1.0. The largest source of uncertainty is a systematic difference in f-values between those derived via the Holweger-Muller (1974) solar model and the Bell et al. (1976) solar model. If we use absolute f-values measured by the Oxford group (Blackwell et al. 1982) we find Fe/H to lie in the range of -0.6 to -0.75, i.e., as given by using the Bell et al. solar model. The relative abundances of the light elements, i.e., Na through Ca and probably including Ti show an average excess relative to iron of 0.4-dex. The effect of this difference on metal indices derived from broad- and narrow- band photometry is discussed. For three stars we find O/H = -0.6 using absolute f-values. For CN an analysis of individual rotational lines of the 2-0 band of the red system yields lines in the (C/H, N/H) plane that are consistent with either an original C/Fe = N/Fe = 0 or a modest increase in N relative to C due to CN burning and mixing. A search for C-13N was not successful and an uncertain lower limit of C-12/C-13 near 10 was obtained.

Leep, E. Myckky↗
NASA NTRS1989

Stable carbon and sulfur isotopes as records of the early biosphere

The abundance ratios of the stable isotopes of light elements such as carbon and sulfur can differ between various naturally-occurring chemical compounds. If coexisting compounds have achieved mutual chemical and isotopic equilibrium, then the relative isotopic composition can record the conditions at which equilibrium was last maintained. If coexisting chemical compounds indeed formed simultaneously but had not achieved mutual equilibrium, then their relative isotopic compositions often reflect the conditions and mechanisms associated with the kinetically controlled reactions responsible for their production. In the context of Mars, the stable isotopic compositions of various minerals might record not only the earlier environmental conditions of the planet, but also whether or not the chemistry of life ever occurred there. Two major geochemical reservoirs occur in Earth's crust, both for carbon and sulfur. In rocks formed in low temperature sedimentary environments, the oxidized forms of these elements tend to be enriched in the isotope having the larger mass, relative to the reduced forms. In sediments where the organics and sulfides were formed by biological processes, these isotopic contrasts were caused by the processes of biological CO2 fixation and dissimilatory sulfate reduction. Such isotopic contrasts between oxidized and reduced forms of carbon and sulfur are permitted by thermodynamics at ambient temperatures. However, nonbiological chemical reactions associated with the production of organic matter and the reduction of organics and sulfides are extremely slow at ambient temperatures. Thus the synthesis of organics and sulfides under ambient conditions illustrates life's profound role as a chemical catalyst that has altered the chemistry of Earth's crust. Because the stable isotopes of carbon and sulfur can reflect their chemistry, they are useful probes of the Martian surface.

Desmarais, David J.↗
NASA NTRS1989

Cosmogenic nuclides in cometary materials: Implications for rate of mass loss and exposure history

As planned, the Rosetta mission will return to earth with a 10-kg core and a 1-kg surface sample from a comet. The selection of a comet with low current activity will maximize the chance of obtaining material altered as little as possible. Current temperature and level of activity, however, may not reliably indicate previous values. Fortunately, from measurements of the cosmogenic nuclide contents of cometary material, one may estimate a rate of mass loss in the past and perhaps learn something about the exposure history of the comet. Perhaps the simplest way to estimate the rate of mass loss is to compare the total inventories of several long-lived cosmogenic radionuclides with the values expected on the basis of model calculations. Although model calculations have become steadily more reliable, application to bodies with the composition of comets will require some extension beyond the normal range of use. In particular, the influence of light elements on the secondary particle cascade will need study, in part through laboratory irradiations of volatile-rich materials. In the analysis of cometary data, it would be valuable to test calculations against measurements of short-lived isotopes.

Herzog, G. F.↗
NASA NTRS1990

Nature and origin of interstellar diamond from the Allende CV3 meteorite

Data and experimental evidence which support the contention that the C delta diamonds may result from grain-grain collisions in supernova shocks in the interstellar medium are presented. Fragments of the Allende CV3 chondrite were acid-treated. A whitish powder was obtained. For the Analytical Electron Microscopy (AEM) a small drop of ethanol suspension was transferred onto holey carbon support films on 3 mm EM grids. The AEM was performed on transmission-thin fragments of the material which overlay holes in the film, to eliminate interference from the substrate. Electron Spectroscopy for Chemical Analysis (ESCA) was performed on a large aliquot of C. Diamond was identified by selected area electron diffraction. Scanning Transmission Electron Microscope / Energy Dispersive X-ray (STEM-EDS) microanalyses of the C delta diamond, using a light-element detector, show that oxygen and possibly nitrogen are the only impurities consistently present. ESCA spectra from bulk C delta material confirm the presence of N at a level of 0.35 percent or less. Under UV irradiation a yellow-red fluorescence is observed, consistent with that of natural diamonds containing substitutional N. Electron Energy Loss Spectra (EELS) were recorded at 2 eV resolution from the C delta diamond, high pressure synthetic diamond, a diamond film produced in a low pressure plasma by chemical vapor deposition (CVD) on a heated silicon substrate (Roy, 1987), graphite, and amorphous arc sputtered carbon. Comparison of the carbon K edge shape and fine structure shows the Allende C delta phase to be largely diamond, but with a significant pre-edge absorption feature indicative of transitions of C 1s electrons into pi asterisk orbitals which are absent in the purely sp(3)-bonded diamond but present in graphite and amorphous carbon.

Blake, David↗