Effects of proton irradiation on a gas phase in which condensation takes place. I Negative Mg-26 anomalies and Al-26

Abstract

view Abstract Citations (13) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Effects of proton irradiation on a gas phase in which condensation takes place. I. Negative 26Mg anomalies and 26Al. Heymann, D. ; Dziczkaniec, M. ; Walker, A. ; Huss, G. ; Morgan, J. A. Abstract In the present paper, isotopic effects in magnesium generated in a proton-irradiated gas phase are examined, taking only (p,n), (p,d), and (p, alpha) reactions in magnesium, aluminum, and silicon into consideration. In the presence of proton radiation, the three elements are 'removed' from the gas phase by condensation. It is required that a value of Al-26/Al-27 greater than 6 times 10 to the -5th must be reached, consistent with the value deduced by Lee Papanastassiou, and Wasserburg (1976) from their studies of the Allende meteorite. The calculations show that fast aluminum condensation reduces the required proton fluence substantially, that a significant fraction of aluminum remains uncondensed when the above value of the Al-26/Al-27 ratio is reached, that a detectable MG-24 excess is very likely to occur, that detectable negative MG-28 anomalies can be generated, and that proton fluxes and irradiation times can be varied simultaneously, and over a wide range of values, without significant changes in the required proton fluence. Publication: The Astrophysical Journal Pub Date: November 1978 DOI: 10.1086/156570 Bibcode: 1978ApJ...225.1030H Keywords: Aluminum 26; Astronomical Models; Magnesium Isotopes; Meteoritic Composition; Nuclear Reactions; Proton Irradiation; Abundance; Aluminum 27; Differential Equations; Energy Spectra; Proton Energy; Proton Flux Density; Solar System; Time Dependence; Vapor Phases; Lunar and Planetary Exploration; Physics full text sources ADS |