The Production of radio isotopes in collisions of cosmic ray nuclei with hydrogen in space and the effect of their decay on the composition of the radiation observed near the earth

Abstract

The effects arising from the decay of radio isotopes produced in collisions of cosmic-ray nuclei with hydrogen in space, on the composition of the radiation observed in the neighbourhood of the earth have been investigated. The production cross sections for all the individual isotopes resulting from such collisions have been deduced using the available experimental data and an empirical relation due to Rudstam. The calculations show that: (a) The cosmic radiation should have traversed an amount of 2.5±0.5g/cm² of hydrogen between the source region and the earth; (b) the calculated relative intensities of Li, Be and B nuclei, produced in collisions of heavy nuclei with hydrogen, after taking decay effects into account, agree well with the observed relative intensities of these nuclei in the primary cosmic radiation in the vicinity of the earth; (c) nuclei with Z = 16-19 are very rare near the source region compared to nuclei with Z = 10-15 and Z = 20-28; (d) the decay effects of radio isotopes give rise to pronounced even-odd effects for nuclei with Z = 10-19 and (e) with the available experimental data on the composition of the primary cosmic radiation at the top of the earth's atmosphere and the partial cross sections deduced in this investigation, it is impossible to start with a pure Fe-source for the cosmic radiation and obtain the chemical composition near the earth by spallation processes.