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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Instrumentation

Mass spectrometry, Mossbauer spectrometry, and radioactivity measuring instruments

Haramic, M.↗
NASA NTRS1971

Moessbauer studies of Apollo 12 samples

Phase analysis of Apollo 12 fines, core tube samples and rocks by Mossbauer studies, noting nearly uniform distribution of major Fe containing phases

Abdel-Gawad, M.↗
NASA NTRS1971

Measurement of the gravitational redshift using a clock in an orbiting satellite

A hydrogen maser clock is proposed for enclosure in an orbiting satellite to measure the gravitational effect on time scales with high accuracy. This experiment is used to test the principle of equivalence for clocks in space. Extremely narrow linewidth of Fe-57 radiation and absorption due to Mossbauer effect over 75 ft vertical distance was used to confirm the prediction of the equivalence principle to 1 part in 100. The fractional frequency shift of a satellite-borne oscillator observed from earth is also given.

Vessot, R. F. C.↗
NASA NTRS1972

A computer program for Moessbauer data processing

A computer program to analyze Mossbauer data is presented in detail. The least-squares curve fitting techniques described apply to single line spectra, single hyperfine spectra, or when the constituent spectra are separated well enough to let the individual absorption peaks stand alone. The present program is not adapted for complex spectra resulting from the existence of several local environments in the absorber iron alloy. Sample problems are presented to aid the user in setting up and running the program. The program is written in FORTRAN 4 language for the Control Data 6000 series digital computer with the SCOPE 3.0 operating system and requires approximately 115,000 octal locations of core storage. A typical case with one absorption peak runs in 20 seconds, and a typical problem with six absorption peaks requires 50 seconds.

Howser, L. M.↗
NASA NTRS1972

The significance of the redshift rocket probe experiment to the theories of gravitation

Direct measurements of the effects of gravitation on time are discussed. Using the earth's gravity these measurements can now be made to 20 parts per million. At present, there is a 1% verification of the equivalence principle for clocks made over a 75-ft vertical distance by use of Mossbauer gamma ray emission and absorption. Measurements made to greater accuracy and spanning distances where appreciable curvature of the metric of spacetime will help verify the equivalence principle, a postulate upon which Einstein developed his General Theory of Relativity.

Vessot, R. F. C.↗
NASA NTRS1971

Oxidation state of iron in plagioclase from lunar basalts.

Determination of the oxidation state of iron in the plagioclase from the coarse-grained basalts 10044 and 12021, using Mossbauer spectroscopy. The location of iron in the crystal structure was also investigated. The spectra show that iron is in the high-spin ferrous state, and they located at least two distinct positions with different coordination numbers. Some excess resonant absorption is probably due to Fe(3+), although the Fe(3+) doublet could not be positively resolved.

Hafner, S. S.↗
NASA NTRS1972

Hyperfine interactions of Fe/2+/ in ilmenite.

Hyperfine interactions at the Fe(2+) sites in ilmenite have been determined by Mossbauer spectroscopy. At 5 K, the internal magnetic field is -43 (plus or minus 3) kOe, and the quadrupole coupling constant is +1.44 (plus or minus 0.01) mm/sec. Theoretical interpretation of the internal magnetic field in terms of dipolar-, orbital-, and core-polarization contributions is shown to depend critically upon the still unknown lattice contribution to the quadrupole coupling constant.

Grant, R. W.↗
NASA NTRS1971

Moessbauer spectra of ferrite catalysts used in oxidative dehydrogenation

Room temperature Mossbauer spectroscopy was used to examine bulk changes which occur in low surface area CoFe2O4 and CuFe2O4 catalysts as a result of contact with various mixtures of trans-2-butene and O2 during oxidative dehydrogenation reactions at about 420 C. So long as there was at least some O2 in the gas phase, the CoFe2O4 spectrum was essentially unchanged. However, the spectrum changed from a random spinel in the oxidized state to an inverse spinel as it was reduced by oxide ion removal. The steady state catalyst lies very near the fully oxidized state. More dramatic solid state changes occurred as the CuFe2O4 underwent reduction. Under severe reduction, the ferrite was transformed into Cu and Fe3O4, but it could be reversibly recovered by oxidation. An intense doublet located near zero velocity persisted in all spectra of CuFe2O4 regardless of the state of reduction.

Cares, W. R.↗
NASA NTRS1973

High voltage electron microscopy of lunar samples

Lunar pyroxenes from Apollo 11, 12, 14, and 15 were investigated. The iron-rich and magnesium-rich pyroxene specimens were crushed to a grain size of ca. 50 microns and studied by a combination of X-ray and electron diffraction, electron microscopy, 57 Fe Mossbauer spectroscopy and X-ray crystallography techniques. Highly ordered, uniform electron-dense bands, corresponding to exsolution lamellae, with average widths of ca. 230A to 1000A dependent on the source specimen were observed. These were?qr separated by wider, less-dense interband spacings with average widths of ca. 330A to 3100A. In heating experiments, splitting of the dense bands into finer structures, leading finally to obliteration of the exsolution lamellae was recorded. The extensive exsolution is evidence for significantly slower cooling rates, or possibly annealing, at temperatures in the subsolidus range, adding evidence that annealing of rock from the surface of the moon took place at ca. 600 C. Correlation of the band structure with magnetic ordering at low temperatures and iron clustering within the bands was studied.

Fernandez-Moran, H.↗