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  • 1
    ISSN: 1434-6079
    Keywords: 34.80.Kw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dielectronic recombination (DR) of Ar15+(1s 22s) ions was studied in a single-pass merged-beams experiment at the UNILAC (universal linear accelerator) of GSI. Absolute recombination rates and cross sections were measured for electron-ion center-of-mass energies from 0 to 580 eV. A number of Rydberg states formed by DR with 2s → 2p (Δn=0) and 2s → 3ℓ (Δn=1) core excitations and even individual terms in the 1s 23ℓ3ℓ′ configuration could be resolved. Theoretical calculations of DR cross sections are in good overall agreement with the data. In the calculations for Δn=0 transitions, effects of electric fields have to be included to reproduce the magnitude of the measured DR rates at the limit of the 2 p 1/2ℓ and 2 p 3/2ℓ Rydberg series. Discrepancies between theory and experiment are observed at the series limits of the (1s 23ℓnℓ′) Rydberg series.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-06-07
    Description: A set of experiments were carried out to test the feasibility of determining unfractionated elemental and isotopic ratios for the noble gases in the presumably ancient solar wind present in the gas rich meteorites. The problems of diffusive loss was avoided by analyzing metal rather than the usual silicates. In order to avoid chemical, and even harsh physical, treatment of the sample, which might have affected the surfaces of metal grains, a means of analyzing the metal in the presence of residual silicate not removed by gentle crushing and magnetic separation was devised. Preliminary results given were obtained by taking advantage of the differing properties of metal and silicates with regard to diffusion. The results suggests that, with some modifications in the choice of pyrolysis and combustion temperatures and in the amount of O2 used, it should be possible, by oxidizing the surfaces of metal grains from gas rich meteorites, to obtain data on solar wind that has not been fractionated by diffusive loss.
    Keywords: SOLAR PHYSICS
    Type: Lunar and Planetary Inst. Workshop on Past and Present Solar Radiation: The Record in Meteoritic and Lunar Regolith Material; p 12-13
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-28
    Description: Analysis of lunar surface samples for elements implanted therein by solar corpuscular radiation reveals evidence for the following compositional changes over a time period between 1.5 and 3 Gyr: 50-percent decreases in the ratios He-4/Ar-36 and Xe/Ar-36; a 20-percent increase in the ratio He-3/He-4; a 3-percent increase in the ratio Ne-20/Ne-22; and a 50-percent increase in the ratio N-15/N-14. The causes of these changes are not resolved at this time but may include (1) a change in acceleration conditions of the solar wind, (2) a change in flux of solar energetic particles relative to that of the solar wind, and (3) a change in composition of the solar convective zone. There is good evidence for a long-term decrease in the solar-wind flux.
    Keywords: SOLAR PHYSICS
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