Study of the cadmium isotopes (II): Beta and gamma ray spectroscopy of In 110

Abstract

The beta-rays, the internal conversion electrons and the gamma-rays emitted in the decay of In 110 and In 110m have been studied using beta-ray spectrometers and scintillation spectrometers. Sources are produced by the Ag 107(α, n)In 110 and Ag 109(α, 3n)In 110 reactions. Half-lives of both isomers are measured to be 4.9±0.2 h and66±2 min. The maximum energy of the beta-ray of In 110 (66 min) is determined to be 2.20±0.02 MeV. The weak beta-ray of In 110m (4.9 h) is found by means of the triple coincidence method. Many gamma-transitions of In 110m and In 110 are obtained from the internal conversion spectra and the summing peak and the coincidence spectra, as shown in tables 3, 4, 7 and 8. The decay scheme is established, using Ritz's law, Kirchhoff's law, the cascade relation and the selection rule. The new levels of 3.122, 2.249, 2.126 and 2.005 MeV are proposed for Cd 110, in addition to the decay of Ag 110m. Remarkable points are as follows: (1) The 0.121 MeV gamma-ray which is assigned as M1 or E2 by means of the K/(L + M) ratio is estimated to be the gamma-ray following the low energy isomeric transition, (2) the beta-transition from In 110 to the 1.474 MeV levels is observed and (3) the reduced transition probabilities of high energy gamma-rays(⪆ 1 MeV) are much smaller than other low energy transitions. The weak and the intermediate coupling collective models and the asymmetric rotor model are compared with these experimental results. The systematics of the even nuclei in the cadmium region are described. (1) The energies of the first 2 + states show a maximum at A = 110. In the cadmium odd-mass nuclei the spins and parities of the ground states change from 5/2 + to 1/2 + between A = 109 and 111. (2) The energy of the 3+ state is nearly equal to the sum of the first 2+ and 4+ states, rather than that of the first and the second 2+ states. (3) The reduced transition probability from the ground state to the first 2+ state depends linearly on the energy between these states. (4) The reduced transition probabilities of the high energy gamma-rays(⪆ 1 MeV) between the higher excited states are much smaller than those of the low energy gamma-rays from the same state, just as the cascade and the crossover transitions from the second excited state. (5) The log ft value of the transition from the low spin isomer to the second 2+ state is larger than the values to the ground and the first excited states, and there is a beta-transition having a small log ft value which is fed from each high spin isomer to a higher excited state. It was tried to explain these systematics by the superfluid model of the nucleus.