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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

He, Ne and Ar in chondritic Ni-Fe as irradiation hardness sensors.

Noble gas analyses of the Ni-Fe of 9 L, 5 H, and 2 LL chondrites quantitatively support previous suggestions of radiogenic He-4 recoil and He-3 deficits. Furthermore, noble gases in the Ni-Fe show evidence for in situ produced radiogenic He-4 and in some cases for recoil loss of Ar-38 and gain of Ne-21. The ratio of spallogenic Ar-38 and Ne-21 in the metal phase is found to correlate strongly with He-3/Ne-21 and Ne-22/Ne-21 in bulk samples of these chondrites. This is proof of the dependence of these ratios on the irradiation hardness experienced by the meteoroid in space. 'Hardness indices' n equals 1.9-2.2 are found, indicating that on the average the stone meteoroids from which the samples came were smaller in mass than iron meteoroids. The spallogenic Ne-21/Ar-38 ratio in metallic Ni-Fe can be used with the semi-empirical production model deduced from the Grant iron meteorite to calibrate spallogenic He-3/Ne-21 and Ne-21/Ar-38 in bulk samples of L, LL and H chondrites for meteoroid size and sample location allowing the estimation of minimal meteoroid masses.

Nyquist, L.↗
NASA NTRS1974

Multiplet effects on the L/sub 2,3/ fluorescence yield of multiply ionized Ar

The 2p fluorescence yield of Ar in the presence of zero to six 3p holes has been calculated by statistically averaging the fluorescence yields of initial states that consist of individual multiplet configurations, formed by coupling the 2p vacancy to the partially filled 3p shell. The L(sub 2,3) fluorescence yields for the (2p)-1 (3p)-n configurations of Ar are found to be 1.48, 17.97, 24.83, 37.84, 79.61, 112.16, and 121.48 x .0001 for n = 0, 1, 2, 3, 4, 5, and 6, respectively. Results agree reasonably well with experimental fluorescence yields deduced from ion-atom collision measurements.

Chen, M. H.↗
NASA NTRS1974

K-Ar analysis of Apollo 11 fines 10084

Regolithic history of Mare Tranquillitatus is studied with rare gas and mass spectrometric techniques. Grain size-ordinate intercept analysis is applied to bulk soil, ilmenite, and plagioclase separates obtained from 1 mm or smaller fines sample 10084,48. K-Ar ages for ilmenite, plagioclase, and total soil separates are determined to be 2.80, 3.38 and 4.00 AE, respectively. It appears that 10084,48 may consist primarily of two components. In this view, the first is locally derived, forms 65-75% of the present day regolith and may show that a local degassing event(s) occurred between 2.8 and 3.5 AE ago. The second component is similar to material from the lunar highlands. It may be local or foreign in origin and contributes the remaining 25-35% of the soil. This component exhibits an age of 4.00 AE and is either slightly older than, or contemporaneous with, the oldest of the returned Apollo 11 basalts. Within the limits of experimental error, the trapped Ar-38/Ar-36 ratio is constant at 0.1890 for all the soil components examined.

Basford, J. R.↗
NASA NTRS1974

Episodic release of Ar-40 from the interior of the moon

Measurements of lunar atmosphere made by the mass spectrometer at the Apollo 17 landing site during the first 9 lunations of 1973 show an apparently cyclical variation of radiogenic Ar-40, with maximum to minimum abundance ratio of about 2. There seems to be a 6-7 month periodicity in the oscillation, but the limited data base makes a fixed oscillatory pattern uncertain. The significance of the variation of atmospheric argon lies in the implication that its source is episodic in nature, ranging in strength from about 1% of the total rate of production of Ar-40 in the moon to near zero. This requires a presently active mechanism for transient venting of gas from deep within the moon.

Hodges, R. R., Jr.↗
NASA NTRS1976

Adsorption of Ar on a nonuniform MgO surface

Data are presented for the adsorption of Ar and N2 on a strongly heterogeneous MgO surface at 84 K and for Ar at a range of temperatures between 130 and 250 K. The high-temperature data are analyzed according to a model which separates the contributions to the potential into bulk and surface terms, providing a method for the determination of the surface area from parameters characteristic of the bulk material. A solid-gas energy parameter and parameters indicating the strength of the impurity sites are also evaluated.

Hinman, D. C.↗
NASA NTRS1976

Ar-40/Ar-39 dating of collisional events in chondrite parent bodies

Ar-40/Ar-39 age dating of a number of shocked ordinary chondrites is interpreted in terms of collisional degassing events of meteorite parent bodies, probably in the asteroid belt. Examples of L, H, and at least one LL chondrite show episodic degassing. Degassing ages suggest several distinct events ranging from about 0.03 aeon to 0.7 aeon and probably higher. All specimens of either the H or L chondrites are not consistent with a single age event. A direct correlation exists between the degree of shock heating and the fraction of argon lost during degassing. However, no chondrite yet analyzed shows complete degassing of its high-temperature phase. Consequently, whole rock K-Ar ages are not accurate monitors of the time of the shock event.

Bogard, D. D.↗
NASA NTRS1977

Studies of Ar and N2 using threshold photoelectron spectroscopy by electron attachment /TPSA/

Threshold photoelectron spectra of Ar and N2 are studied by a technique called threshold photoelectron spectroscopy by electron attachment, which involves the attachment of the threshold electron to SF6 followed by the detection of SF6(-). Studies on Ar provide a measure of the rejection ratio for nonthreshold electrons of this technique. A rotational propensity rule is given which states that an autoionizing N2 state prefers to decay to N2(+) states with a minimum change in rotational angular momentum.

Chutjian, A.↗
NASA NTRS1977

AR-39Ar-40 dating of basalts and rock breccias from Apollo 17 and the malvern achondrite

The principles and the potential of the Ar-39/Ar-40 dating technique are illustrated by means of results obtained for 12 Apollo 17 rocks. Emphasis is given to methodical problems and the geological interpretation of lunar rock ages. Often it is ambigious to associate a given lunar breccia with a certain formation, or a formation with a basin. In addition, large-scale events on the Moon have not necessarily reset radiometric clocks completely. One rock fragment has a well-defined plateau age of 4.28 b.y., but the ages of two Apollo 17 breccias define an upper limit for the formation age of the Serenitatis basin at 4.05 b.y. Ages derived from five mare basalts indicate cessation of mare volcanism at Taurus-Littrow approximately 3.78 b.y. ago. Ca/Ar-37 exposure ages show that Camelot Crater was formed by an impact approximately 95 m.y. ago. After a short summary of the lunar timetable as it stands at the end of the Apollo program, we report about Ar-39/Ar-40 and rare gas studies on the Malvern meteorite. This achondrite resembles lunar highland breccias in texture as well as in rare-gas patterns. It was strongly annealed at some time between 3.4 and 3.8 b.y. ago. The results indicate that very similar processes have occurred on the Moon and on achondritic parent bodies at comparable times, leading to impact breccias with strikingly similar features, including the retention of rare-gas isotopes from various sources.

Kirsten, T.↗
NASA NTRS1980

Large volume multiple path nuclear lasing of /He-3/-Ar

Output power of 550 W has been achieved from a nuclear-pumped multiple path laser system containing (He-3)-Ar by using the (He-3)(n, p)3(H) nuclear reaction for power deposition. Lasing was achieved in Ar at 1790 nm. The complex beam profile was resolved by an InAs array detector. Laser output was directly proportional to thermal neutron flux, and also increased proportionally with increasing (He-3) pressure up to 292.6 kPa. The variation of the laser output power with the number of passes through the excited medium was found to peak at 5-7 passes.

De Young, R. J.↗
NASA NTRS1981

Kilowatt multiple-path He-3-Ar nuclear-pumped laser

Nuclear lasing of He-3-Ar at 2300-torr total pressure with a thermal neutron flux of 4.3 x 10 to the 16th n/sq cm-sec has resulted in a lasing output power of 1012 W. A multiple-path laser cavity was used with seven passes through the laser medium which was pumped by the He-3(n, p)H-3 nuclear reaction. The thermal neutron lasing threshold flux was 1 x 10 to the 16th n/sq cm-sec. At 600-Torr He-3-(2%)Ar, the threshold flux was 4.7 x 10 to the 15th n/sq cm-sec. This represents the highest-power, largest-volume nuclear laser to date.

Deyoung, R. J.↗
NASA NTRS1982

AR Pavonis - The Rosetta Stone of the symbiotics

AR Pav is considered with respect to the early history and observations, the light curve, spectroscopic properties, and recent observations. It is suggested that recent observations tend to confirm the validity of the binary model proposed for AR Pav by Thackeray and Hutchings (1974). The secondary appears as an M3 giant showing normal infrared properties. The nature of the hot primary, however, remains uncertain as it appears obscured by an accretion 'shell' both during and outside of eclipse.

Slovak, M. H.↗
NASA NTRS1985

Measurements of Fe and Ar fragmentation cross sections

Measurements are reported of the yields of individual isotopes of Cr to Co(Z = 24 to 27) resulting from the fragmentation of Fe-56, and the isotopes of Mg to K(Z = 12 to 19) resulting from the fragmentation of Ar-40. Recent advances in the resolution and collecting power of cosmic ray instrumentation, have led to dramatic improvements in the precision of cosmic ray composition measurements, both elemental and isotopic. The interpretation of these measurements is presently limited by uncertainties in the fragmentation cross-sections needed to correct for nuclear interactions with the interstellar gas. Cosmic ray propagation codes now rely mainly on semi-empirical cross-section formulae developed by Silberberg and Tsao (S&T), which have a typical uncertainty of approximately 25%. Relative isotope yields from the fragmentation of approximately 380 MeV/nucleon Fe-56 e and approximately 210 MeV/nucleon Ar-40 r in CH2 targets, observed during the calibration of two cosmic ray spectrometers at the Lawrence Berkeley Laboratory Bevalac are reported. These are compared with calculated yeilds based on the S&T cross-section formulae.

Lau, K. H.↗
NASA NTRS1986

Lower thermosphere densities of N2, O and Ar under high latitude winter conditions

Measurements of the neutral thermosphere were conducted in northern Scandinavia during the Energy Budget Campaign. These measurements included determinations of N2, O, and Ar densities using rocket-borne experiments. The results obtained in the experiments are presented, taking into account also details regarding the employed experimental methods, and an evaluation of the significance of the data. It is found that there are striking differences in thermospheric distributions of the neutral constituents under different geomagnetic conditions. Under quiet geomagnetic conditions there was reasonable agreement with the United States Standard Atmosphere. The concentrations of N2 and Ar were about 70 percent of the predicted values, while the O concentration was about 2.5 times greater.

Dickinson, P. H. G.↗
NASA NTRS1987

Rotational modulation and flares on RS CVn and BY Dra stars. III - IUE observations of V711 Tau (= HR 1099), II Peg, and AR Lac

Observations of three RS CVn stars, which were obtained over the stellar rotation cycles with the IUE satellite, are presented. Emission lines from high-temperature transition regions and chromospheres analogous to those observed in the solar spectrum were observed. The only visible component of II Peg and both components of V711 Tau and AR Lac appear to be chromospherically active. For the latter systems, the Mg II line surface flux from the G-type star is higher than that from the K subgiant, which dominates the observed UV line flux. Moreover, evidence of long-term ultraviolet variability is presented for AR Lac. The emission line fluxes for II Peg and, marginally, for the other two systems were observed to vary in antiphase with the optical variations at the time of the IUE observations. By comparing the results of Rodono et al. (1986) for two-spot models with the variation of UV line flux, evidence of a close spatial correlation between spot and plagelike features is found.

Rodono, M.↗
NASA NTRS1988

Trapping Ne, Ar, Kr, and Xe in Si2O3 smokes

Simple Si2O3 smokes have been condensed at both low (less than 750 K) and high (greater than 1000 K) temperature at 35 torr H2 pressure in the presence of 0, 10, 100, and 1000 microns of a noble gas mixture containing Ne, Ar, Kr, and Xe. In general, both Ne and Ar are quite loosely bound in the smokes (6.0 x 10 to the -8th and 2.6 x 10 to the -4th ccSTP/g, respectively), and are degassed at temperatures below 1200 K. Both Kr and Xe are somewhat more strongly bound at concentrations of 1.0 x 10 to the -7th and 8.2 x 10 to the -8th ccSTP/g, respectively, and in addition show a double release with a second component at a temperature of about 1875 K. With the exception that Si2O3 smokes appear to show a particular affinity for argon, possibly due to an anomalous absorption of atmospheric argon, none of the other noble gases are found in sufficient concentration to explain the gases observed in meteorites as primary circumstellar condensates. However, this data in conjunction with observations of Honda et al. (1979) do seem to show a degree of dependence between noble gas retention and chemical composition.

Nuth, Joseph A., III↗
NASA NTRS1991

Ar-40/Ar-39 ages of six Apollo 15 impact melt rocks by laser step heating

Fifteen high resolution (21-51 step) Ar-40/Ar-39 age spectra are obtained for six Apollo 15 impact melt rocks of different compositions, using a continuous laser system on submilligram subsamples and on single crystal plagioclase clasts. Four of the six samples gave reproducible age spectra with well-defined intermediate temperature plateaus over 48 percent or more of the Ar-39 released; the plateaus are interpreted as crystallization ages. Samples 15304,7,69, 15294,6,21 and 15314,26,156 gave virtually identical plateau ages whose weighted mean is 3870 + or - 6 Ma. These three melt rocks differ in composition and likely formed in three separate impact events.

Dalrymple, G. B.↗
NASA NTRS1992

Self-, N2, O2, H2, Ar, and He broadening in the nu3 band Q branch of CH4

Self-, N2-, O2-, H2-, Ar-, and He-broadening coefficients, pressure shifts, and integrated intensities have been measured for most transitions in the Q branch of the nu3 fundamental band of methane using a difference-frequency laser spectrometer. A systematic dependence of the broadening coefficients on the tetrahedral symmetry species and order index is observed with striking similarities for N2, O2, and Ar and for H2 and He buffer gases. Comparison with earlier measurements on other bands and branches of methane indicates very little vibrational, branch, or carbon isotope dependence. Dicke narrowing is evident at intermediate pressures, yielding an average narrowing coefficient and an optical diffusion constant for each gas mixture.

Pine, A. S.↗
NASA NTRS1992

Accurate oscillator strengths for ultraviolet lines of Ar I - Implications for interstellar material

Analysis of absorption from interstellar Ar I in lightly reddened lines of sight provides information on the warm and hot components of the interstellar medium near the sun. The details of the analysis are limited by the quality of the atomic data. Accurate oscillator strengths for the Ar I lines at 1048 and 1067 A and the astrophysical implications are presented. From lifetimes measured with beam-foil spectroscopy, an f-value for 1048 A of 0.257 +/- 0.013 is obtained. Through the use of a semiempirical formalism for treating singlet-triplet mixing, an oscillator strength of 0.064 +/- 0.003 is derived for 1067 A. Because of the accuracy of the results, the conclusions of York and colleagues from spectra taken with the Copernicus satellite are strengthened. In particular, for interstellar gas in the solar neighborhood, argon has a solar abundance, and the warm, neutral material is not pervasive.

Federman, S. R.↗