The reaction Mg(n,α)Ne at 14.1 and 14.7 MeV: cross sections and implications for meteorites

Abstract

Mass spectrometric analyses of neutron-irradiated targets of natural magnesium yield cross sections of59 ± 14,160 ± 8, and11.0 ± 3.3mb for 20Ne, 21Ne, and 22Ne, respectively, at 14.1 MeV and of94 ± 8,152 ± 12, and13.0 ± 2.0mb at 14.7 MeV. With the incorporation of these cross sections, calculations modeling cosmic-ray interactions in stony meteoroids of radii 20 and 26 cm predict that between the surface and center the 22Ne/ 21Ne ratio falls more than 10% while the 21Ne production rate rises about 30%. The reaction 24Mg(n,α) 21Ne predominantly controls these trends: the 22Ne/ 21Ne ratio due to magnesium decreases over 15% while that due to silicon remains constant with increasing depth. The calculations are compared with published neon measurements for the Keyes and St. Séverin meteorites.