THE GAMOW-TELLER DECAY OF SN-105 TO 3-PARTICLE STATES IN IN-105

The EC/beta(+) decay of Sn-105 was reinvestigated by using Ni-58(5 MeV/u) +Cr-50 reactions, chemically selective on-line mass separation and gamma-ray spectroscopy. The half-life of Sn-105 has been determined as 34 +/- 1 s. Out of 104 gamma transitions ascribed to the Sn-105 decay, 89 have been placed in the decay scheme including 52 excited states of In-105. From the EC/beta(+) feeding of individual states, the distribution of the Gamow-Teller (GT) strength has been derived. It is shown that the main part of the GT strength is associated with the feeding of In-105 levels having excitation energies above 3 MeV. This observation can be interpreted as a sign of dominant feeding of three-quasiparticle states in In-105, which correspond to the pi(g(9/2))(-1)nu g(7/2)nu d(5/2) shell-model configuration spread over many levels. The sum of the GT strength deduced from the present gamma-ray data of B-Sigma(GT) = 1.46 provides a lower limit to the total GT strength. Many weak transitions, mainly from high-energy levels, may not have been detected in this study and therefore part of the strength may be missed. An indirect support for this conclusion has been obtained from the analysis of the indium KX-rays intensity. This analysis indicates about 50% contribution of the electron-capture to the beta decay of Sn-105, which is interpreted as a sign of a predominant feeding of the high-energy In-105 states with B-Sigma(GT) greater than or equal to 3. The observed GT distribution and strength will be compared to results obtained from a finite-Fermi-system theory and a large-basis shell-model calculation. The core-polarization and higher-order hindrance factors will be discussed.