Beta decay of neutron-deficient even-mass indium isotopes: Evidence for population of highly-excited states in the cadmium-daughter nuclei

By using mass-separated sources, positrons as well as β-delayed protons and γ-rays were measured from the β-decay of ¹⁰²In (T _{1 2} = 22 ± 1 s) and ¹⁰⁰In (T _{1 2} = 6.1 ± 0.9 s). In particular, the average β⁺ (β⁺ + EC) ratio for the decay of ¹⁰²In was measured to be 0.76(4) and the level scheme of ¹⁰²Cd was extended. Whereas no direct β⁺ EC feeding of the identified ¹⁰²Cd levels was observed, there is evidence for population of ¹⁰²Cd states at high excitation energy followed by statistical γ-decay. This feature, which has been deduced on the basis of the measured positron spectrum and the measured β⁺ (β⁺ + EC) ratio of the ¹⁰²In decay, is compared to the decay properties of the heavier odd-odd indium isotopes ¹⁰⁴In, ¹⁰⁶In and ¹⁰⁸In, and is also used to interpret the observed β-delayed proton data of ¹⁰²In and ¹⁰⁰In. For the first time, large-space shell-model calculations have been performed for the Gamow-Teller decay of heavy odd-odd nuclei. The decay results from these calculations are in good overall agreement with the gross decay properties of ¹⁰²In and ¹⁰⁰In deduced from the experiment.