Isotopic Anomalies of Xenon from Tellurium minerals

Abstract

Xenon extracted from old tellurium minerals were analyzed with a high-sensitivity mass spectrometer. Old tellurium minerals of different four localities were used in the experiments, that is, tetradymite(Bi₂ Te₂S)from the Oya mine, tellurobismuthite(Bi₂ Te₃)from the Suwa mine, tellurium mineral(AgAuTe+Te)from the Rendai-ji mine and native tellurium(Te)from the Teine mine. In heating the sample minerals, the temperature was raised stepwise typically by100°C and kept constant for a hour. Rare gases extracted at step of extraction temperature were purified and then sealed up in the respective ampoul. Large excesses in¹²⁹Xe, ¹³⁰Xe and¹³¹Xe extracted from the Oya tellurium mineral and in¹³⁰Xe from the Suwa tellurium mineral were found definitely. Their origins were discussed on the basis of the isotopic amonalies patterns as well as experimental and theoretical considerations on the nuclear reaction relating to the relevant isotopis of xenon. The¹³⁰Xe-excess was attributed to doubleβ-decay of¹³⁰Te. A mall excess in¹²⁸Xe was interested in relation to double β-decay of¹²⁸Te. Several nuclear processes which could contribute to¹²⁸Xe were discussed on the available data. Concerning the isotopic amonalies in¹²⁹Xe and¹³¹Xe, the ratio ¹²⁹Xe-excess/¹³⁰Xe-excess(m=129 and 131)seems to decrease and the ratio¹²⁹Xe-excess/¹³¹Xe-excess seems to increase with the increasing tellurium concentration for the Oya tellurium minerals. We may be able to look for a solution of the amonalies in either the epithermal neutron captures on¹²⁸Te and on¹³⁰Te or both the(μ^-, n)reaction of¹³⁰Te and the themal neutron captures on¹²⁸Te and on¹³⁰Te, where the neutrons can be produced by the(μ^-, n)reactions and the(α, n)recations on the environmental rocks. In order to understand the above results on the ratio between Xe-excess, we may have to take into account the competition process between between the neutron captures on¹²⁸Te and on¹³⁰Te and the neutron adsorptions by the associated impurities, and the(a, n)reactions on¹²⁶Te and on¹²⁸Te respectively.