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Results for “Isotopic composition”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Primary and diagenetic controls of isotopic compositions of iron-formation carbonates

Results are presented on parallel analyses of carbonate and chert microbands in segments from the early Proterozoic Dales Gorge Member of the Brockman Iron Formation (western Australia), including data on isotopic, chemical, and mineralogic variations in microbanded carbonates, cherts, and coexisting minerals in four core segments from Paraburdoo and one from Wittenoom. It is shown that patterns of variation observed in isotopic abundance and mineral composition can be consistently explained in terms of diagenetic replacement of fine-grained primary precipitates by secondary ones, rather than by mineral-dependent fractionations, metamorphism, or the influence of large volumes of water in an open system.

Kaufman, Alan J.↗
NASA NTRS1975

The isotopic composition of galactic cosmic ray Li, Be, and B

New measurements are reported of the isotopes of cosmic-ray Li, Be, and B and of the elements C, N, and O, with cosmic ray telescopes on board the IMP-7 and IMP-8 satellites during 1973-74 in the energy range 35-210 MeV/nucleon. High mass resolution and stability together with a set of data more extensive than in previous experiments lead to a clear isotopic separation. The measured isotopic and chemical abundances provide a stringent test for models of interstellar propagation and solar modulation. We find not only that for a steady state propagation and solar modulation model all light isotopes and medium element abundances are explained by 5 g/sq cm average pathlengths, as was earlier found from element analysis, but that also these results, taken along with our Be-10 measurements, indicate a longer lifetime for cosmic rays than predicted by the usual assumption of an average interstellar density of 1 to 3 atoms/cu cm.

Garcia-Munoz, M.↗
DOE OSTI2023

Developing Methodology to Determine Pu Isotopic Composition by Laser Ablation MC-ICP-MS

This project will develop methodology to analyze the Pu isotope ratio in mixed U-Pu particles by laser ablation MC-ICP-MS. This will involve: 1) testing and validation of the Pu analytical method using mixed U-Pu solutions and Pu doped glasses, 2) isotopic analysis of mixed U-Pu particles by laser ablation MC-ICP-MS, and 3) continued development of the R-based data reduction program. Details regarding the analytical method development and results of QC testing will be output as a deliverable to the IAEA, along with an updated version of the LARA data reduction software.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Study of isotopic composition of helium in the fine fraction of Luna 16 lunar surface material

The content of He isotopes is measured in two samples of the lunar surface material returned by the Luna 16 automatic station. Both samples consist of a fine fraction of lunar surface material and were samples from zone A (sample 3-2k) and from zone V (sample 9-1r). The value of He4/He3 and the concentration of the He isotopes are identical for both samples, within the limits of experimental error.

Boltenkov, B. S.↗
NASA NTRS1993

The elemental and isotopic composition of Galactic cosmic-ray nuclei from scandium through nickel

Measurements of the relative elemental and isotopic abundances of iron-group Galactic cosmic rays at energies of about 325 MeV per nucleon have been made. The source abundance ratio of Ni-60/Ni-58 is 1.07 +/- 0.39, which is a factor of 2.8 +/- 1.0 larger than the solar system value. Our measurements imply the presence of Co-59 at the source, which can be reconciled with the predictions of conventional nucleosynthesis models if there exists a time delay of more than about 100,000 yr between nucleosynthesis and acceleration. Most of the Mn-54 produced by spallation during cosmic-ray propagation in the Galaxy is found to have decayed to Fe-54, indicating a confinement time of greater than 2 Myr. The source ratio of Fe-54/Fe-56 corrected for the Mn-54 decay is 0.046+/- 0.020, which is consistent with the solar system value of 0.063.

Leske, Richard A.↗
NASA NTRS1988

Isotopic composition of cosmic-ray boron and nitrogen

New measurements of the cosmic-ray boron and nitrogen isotopes at earth and of the elemental abundances of boron, carbon, nitrogen, and oxygen are presented. A region of mutually allowed values for the cosmic-ray nitrogen source ratios is determined, and the cosmic-ray escape mean free path is determined as a function of energy using a leaky box model for cosmic-ray propagation in the Galaxy. Relative to O-16, a N-15 source abundance consistent with solar system composition and a N-14 source abundance which is a factor of about three underabundant relative to the solar value are found.

Krombel, K. E.↗
NASA NTRS1991

Systematic study of sulfur isotopic composition in iron meteorites and the occurrence of excess S-33 and S-36

The paper concentrates on isotopic measurements of sulfur in different sulfur-carrier phases: troilite inclusions, Fe-Ni alloy, and schreibersite (possibly including daubreelite). Variations in S-34 isotope ratio are observed in some troilite inclusions, and no evidence of nucleosynthetic sulfur isotopic anomalies are found in the troilite inclusions. Excesses of S-33 and S-36 are observed in both FeNi alloy and schreibersite of Grant, Santa Clara, Tlacotepec, and Gibeon, with schreibersite possessing the greater magnitude of presumably spallogenic S-33 and S-36. It is concluded that the magnitude of the observed fractionation is consistent with troilite dissociation and/or vaporization following a collisional impact.

Gao, Xia↗
NASA NTRS2015

A Procedure to Simultaneously Determine the Calcium, Chromium, and Titanium Isotopic Compositions of Astromaterials

Many elements display both linear (mass-dependent) and non-linear (mass-independent) isotope anomalies (relative to a common reservoir). In early Solar System objects, with the exception of oxygen, mass-dependent isotope anomalies are most commonly thought to result from phase separation processes such as evaporation and condensation, whereas many mass-independent isotope anomalies likely reflect radiogenic ingrowth or incomplete mixing of presolar components in the proto-planetary disk. Coupling the isotopic characterization of multiple elements with differing volatilities in single objects may provide information regarding the location, source material, and/or processes involved in the formation of early Solar System solids. Here, we follow up on the work presented in, and detail new procedures developed to make high-precision multi-isotope measurements of Calcium, Chromium, and Titanium with small or limited amounts of sample using thermal ionization mass spectrometry and multi-collector ICP-MS, and characterize a suite of chondritic and terrestrial standards.

Tappa, M. J.↗
NASA NTRS1988

S-process krypton of variable isotopic composition in the Murchison meteorite

Data are reported which, for the first time, permit the derivation of the full isotopic spectrum of s-process krypton with reasonable precision. It is shown that this s-Kr in a residue from the Murchison meteorite did not originate in one single s-process but rather is a mixture of contributions from stellar environments where the density of free neutrons was not the same. The astrophysical conditions under which this krypton was produced were distinct from those that have been invoked to explain the solar system s-process abundance. Similar to the C-13-rich carbon component in an aliquot of the same residue, the s-process Kr from different astrophysical sites has retained its identity during the accumulation and subsequent history of the meteorite.

Ott, Urlich↗
NASA NTRS2023

The Oxygen Isotopic Composition of Samples Returned From Asteroid Ryugu With Implications for the Nature of the Parent Planetesimal

We present oxygen isotopic analyses of fragments of the near-Earth C b -type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in ∆' 17 O can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope 26 Al, suggests that if lithified at the time of alteration, the parent body was small (<<50 km radius). If the parent planetesimal was large (>50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.

Asteroids↗
NASA NTRS1992

The isotopic composition of iron-group cosmic rays

Measurements are reported of the relative abundances of Mn, Fe, Co, and Ni isotopes in Galactic cosmic rays with energies of about 325 MeV per nucleon. The observed limit (Mn-54)/(Mn-53) of less than 0.25 is significantly less than the value of about 0.8-0.9 expected if Mn-54 were stable, indicating that most of the Mn-54 produced during cosmic-ray propagation in the Galaxy has undergone radioactive decay. Relative source abundances of iron and nickel isotopes, and in particular the ratio (Fe-54)/(Fe-56) = 0.046 +/- 0.020, are generally consistent with solar system values. One exception is the source ratio (Ni-60)/(Ni-58) for which an enhancement by a factor of 2.8 +/- 1.0 over the solar value is found. The isotope (Co-59) is found to make up a sizable fraction of the observed Co, indicating a time delay more than about 100,000 yr between nucleosynthesis and acceleration if this nuclide is synthesized as (Cu-59) or (Ni-59).

Leske, Richard A.↗
NASA NTRS1979

Elemental composition, isotopes, electrons and positrons in cosmic rays

Papers presented at the 16th International Cosmic Ray Conference, Kyoto, Japan, dealing with the composition of cosmic rays are reviewed. Particular interest is given to data having bearing on nucleosynthesis sites, supernovae, gamma-process, comparison with solar system composition, multiplicity of sources, and the energy dependence of composition.

Balasubrahmanyan, V. K.↗
NASA NTRS1985

Interstellar propagation and the isotopic composition of hydrogen in the galactic cosmic rays

Preliminary results of a study of the propagation of the quartet of stable isotopes of hydrogen and helium are reported. A mean pathlength of 7.5 + or - 0.5 g/sq cms at approximately 300 MeV/nucleon is required to explain the low energy deuterium spectrum. This pathlength is consistent with pathlengths derived from the elements with Z 2, but is a (He-3/He-4) measurement of Jordan and P. Meyer (1984). The propagation calculations reported here incorporate the preliminary results of an updated nuclear interaction cross section survey covering the period since the review by J. P. Meyer (1972).

Beatty, J. J.↗
NASA NTRS1983

Elemental and isotopic composition of solar energetic particles - Preliminary results from the Phoenix I telescope

The Phoenix I instrument on the S81-1 mission was designed to resolve isotopes in the charge range He to Ni. Analysis of four periods of moderate flare activity shows no strong evidence for mass dependent acceleration in the range C to Si; indeed, the mass abundance ratios are consistent with 'solar system' composition. However, the average Ne-22/Ne-20 ratio for these periods is 0.060 (+0.045, -0.023), i.e. about one standard deviation below ratios reported earlier for solar energetic neon.

Simpson, J. A.↗
NASA NTRSDate not supplied

Isotopic Compositions of Noble Gases and Nitrogen in the Ryugu Samples Returned by Hayabusa2

In December 2014, the hayabusa2 spacecraft launched to visit the C-type asteroid (162173) Ryugu to bring back surface and subsurface materials to the Earth. The spacecraft arrived at Ryugu on June 27, 2018, and subsequently carried out two touchdowns (TDs) and sample collections. The 1st TD was carried out and collected surface samples, while the 2nd TD was done to collect the impact melt ejecta near the artificial crater made by the small carry-on Impactor operation in April 2019. Samples collected during the 1st and 2nd TDs were stored in Chamber A and C of the Hayabusa2 sample catcher, respectively. Our principal objective is to quantify the indigenous compositions of the Ryugu samples with as little terrestrial contamination as possible. Here we report the isotopic ratios and concentrations of noble gases and nitrogen in the Ryugu samples allocated to the Hayabusa2-initial-analysis-volatile team.

noble gas↗
NASA NTRS1975

The isotopic composition of hydrogen and helium in low energy cosmic rays

The Caltech Electron/Isotope Spectrometer on IMP-7 has been used to identify the isotopes H-2 and He-3 in low energy cosmic rays during solar quiet periods from October 1972 to October 1974. These observations cover the energy intervals 5 to 29 MeV/nuc for H-2 and 7 to 50 MeV/nuc for He-3. The energy spectra of H-1, H-2, and He-3 all fall rapidly with decreasing energy, giving H-2/H-1 and He-3/H-1 ratios essentially independent of energy as expected from adiabatic acceleration. The measured He-4 spectrum, however, was essentially flat over this energy interval, and therefore the H-2/He-4 ratio observed at 1 AU is not simply related to the interstellar abundances of these nuclei. However, comparisons of the H-2/H-1 and He-3/H-1 ratios with calculated spectra are possible.

Mewaldt, R. A.↗