Production rates and proton-induced production cross sections of 129I from Te and Ba: An attempt to model the 129I production in stony meteoroids and 129I in a Knyahinya sample

Abstract

Proton-induced production cross sections of 129I from Te and Ba are presented. Earlier assumptions that Te is the most important target element in meteoroids are confirmed. Based on this data set and the experimental production rates of 129I from thick-target experiments, the production of 129I in stony meteoroids is modeled using a GCR flux density of 4.06 cm^(-2) s^(-1). The results of this modeling must be considered preliminary because the contribution from neutron capture on 128Te needs further investigation. We obtained modeled production rates that agree with experimental results for samples from two medium-sized meteorites (Abee and Knyahinya). However, we find that this model does not describe 41Ca in lunar rocks well and seems to overestimate 129I production in larger bodies, such as Allende. We present elemental production rates from Te and Ba based on our modeling as well as for a model that describes neutron capture products. For 129I analysis of Knyahinya, a novel method to separate Te and analysis using ICP-MS was used, enabling the use of experimental elemental concentrations obtained from the same meteorite to calculate 129I production.