The Gamow-Teller beta decay of100Cd

Abstract

Neutron-deficient isotopes of cadmium were produced in the p(600 MeV)+natSn spaltation reaction. The ISOLDE facility provided mass-separated beams of these isotopes. The production yield was 103 to 104 atoms/s for l~176 and roughly two orders of magnitude less for 98Cd. The properties of the ~~176176176 decay were studied in detail by X-ray, y-ray and conversion electron spectroscopy. Forty nine y-transitions were assigned to this decay, and all but five of them were placed in the decay scheme. The half-life was determined to be 49.1+0.5 s. The QEC value of 3890+70keV was deduced from a comparison of experimental and theoretical /?+/(EC+/~ +) probability ratios. Seven 0+--*1 + Gamow-Teller transitions with log ft values between 3.5 and 4.9 were identified. The total (summed) strength is about five times smaller than predicted by the shell model for the transformation of a g9/2 proton into a g7/2 neutron. The quenching of the Gamow-Teller strength and other questions of nuclear structure are discussed for the ~~176 decay. The properties of 98Cd are inferred by extrapolation of 1~176176176 data, and some preliminary experimental results on 98Cd decay are presented.

Gamow-Teller strength distribution in the beta-decay of100Ag from total-absorption gamma spectrometry

“…This discrepancy could at least partly be explained by unusually large/3-delayed proton branching ratios of 96,98Cd and/or 96'98Ag [17]. The resonance-like/3-feeding of highenergy states, that has been found in this work as well as in other recent experiments [2,3,4,10,13,14], may lead to such an enhanced proton emisson.…”

“…This measurement was carried out in multi-spectrum mode in order to determine contributions from isobaric contaminants including isomeric activity. A contribution of the 49 s l~176 activity, identified through the 0.94 MeV 7-line [10], was estimated to be 3 % of the 1~176 activity at the beginning of the 160 s counting cycle (This means that the admixture of l~176 in the mass separated ion beam was less than 1.5 % compared to l~176 A contribution from 3.6 d l~176 activity was not detected. In this context it should be noticed that both the l~176 and the l~176 activities can influence the GT strength distribution only at low l~176 excitation energies due to small QEC values of 3.89 and 0.36 MeV, respectively [12].…”

Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium

“…Together with transition energies in keV, total intensities are given in percent of beta decays (in parenthesis). According to [10,11], the decay energy Qp_ is 1.45___0.10 MeV count for a weak 147.8 keV transition reported only in [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In the course of these measurements, the 114pd and 114Ag activities were in equilibrium.…”

“…5). This coefficient was derived from the relative intensities of the K-conversion and 7-lines of this transition and the [10,11], the decay energy Qp is 2.62_+0.10 MeV 333 keV E2 transition in 114pd (for the 114Rh decay scheme, see [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]). The theoretical c~K value for the latter transition was used as a reference.…”

“…Data on the GT-strength splitting and over-all quenching in the neutron-rich even Pd isotopes are compared in this paper to the relevant observations for EC/fl+-decays in the neighbourhood of l~176 (see [4] and references quoted therein). They are discussed in terms of nuclear structure models and one conclusion is that the assumption of a spherical nuclear shape may be inadequate here.…”