The excitation functions of Ba (p, X) M Xe (M — 124-136) in the energy range 38-600 MeV; the use of ‘cosmogenic’ xenon for estimating ‘burial’ depths and ‘real’ exposure ages

Abstract

Thin target experiments were performed to obtain the excitation functions of the reactions Ba (p, X) MX.e. The abundances of all stable Xe isotopes and of the radionuclides 127Xe and 131Ba were determined by means of rare gas mass spectroscopy and y -counting, respectively. The excitation functions show marked characteristics leading to strong variations in the proton-induced Xe-ratios as functions of energy. The 131Xe/126Xe ratio - the special lunar anomaly-was found to vary from 1.14 ±0.4 (600 MeV) to 248.8 ± 4.0 (75 MeV). The Reproduction rates and the MXe/126Xe ratios as functions of depths were estimated for 271 geometry utilizing the depth dependent galactic-cosmic-ray (g.c.r.) fluxes of Reedy & Arnold (1972). Substantial isotopic variations for all of the proton-induced Xe ratios were found, sufficient to explain most of the cosmogenic Xe ratios (exceptions are 130Xe, and 132Xe) measured yet in lunar samples with proton-induced reactions on Ba at different depths in the Moon. Actual lunar samples are used to check the validity of the results.