The Gamow-Teller decay of "1"0"5Sn to three-particle states in "1"0"5In

The EC/#beta#"+ decay of "1"0"5Sn was reinvestigated by using "5"8Ni (5 MeV/u) + "5"0Cr reactions, chemically selective on-line mass separation and #gamma#-ray spectroscopy. The half-life of "1"0"5Sn has been determined as 34 #+-# 1 s. Out of 104 #gamma# transitions ascribed to the "1"0"5Sn decay, 89 have been placed in the decay scheme including 52 excited states of "1"0"5In. 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 "1"0"5In levels having excitation energies above 3 MeV. This observation can be interpreted as a sign of dominant feeding of three-quasiparticle states in "1"0"5In, which correspond to the #pi#(g_9_/_2)"-"1 #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 povides 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 "1"0"5Sn, which is interpreted as a sign of a predominant feeding of the high-energy "1"0"5In states with B_#SIGMA#(GT)#>=#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. (orig.)SIGLEAvailable from TIB Hannover: RO 801(94-23) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

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 #beta#-delayed protons and #gamma# rays were measured from the #beta# decay of "1"0"2In(T_1_/_2=22#+-#1 s) and "1"0"0In(T_1_/_2=6.1#+-#0.9 s). In particular, the average #beta#"+/(#beta#"++EC) ratio for the decay of "1"0"2In was measured to be 0.76(4) and a detailed level scheme of "1"0"2Cd was constructed. Whereas no direct #beta#"+/EC feeding of the identified "1"0"2Cd levels was observed, there is evidence for population of "1"0"2Cd states at high excitation energy followed by statistical #gamma# decay. This feature, which has been deduced on the basis of the measured positron spectrum and the measured #beta#"+/(#beta#"++EC) ratio of the "1"0"2In decay, is compared to the decay properties of the heavier odd-odd indium isotopes "1"0"4In, "1"0"6In and "1"0"8In, and is also used to interpret the observed #beta#-delayed proton data of "1"0"2In and "1"0"0In. 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 "1"0"2In and "1"0"0In deduced from the experiment. (orig.)SIGLEAvailable from TIB Hannover: RO 801(94-38) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Structure of high spin states in "1"0"4Sn - E2 and E3 polarization of the "1"0"0Sn core

High spin states in "1"0"4Sn were identified in the reaction "5"8Ni("5"0Cr,2p2n) at 200 MeV and 205 MeV beam energies. The #gamma#-ray energies, intensities, multipolarities, and lifetimes of high spin states were measured with the GASP spectrometer array in combination with a plunger apparatus by means of the recoil distance Doppler shift method. The deduced level scheme and transition probabilities are compared to the results of large-scale shell model calculations using three independent two-body interactions. The agreement of the level energies is satisfactory, except for a cascade of dipole transitions at high spins. The general good agreement found for E2 transition strengths implies a large effective neutron polarization charge. The shell-model calculations do not account for the measured enhanced E3 transitions for which a core excited octupole phonon admixture is indicated. (orig.)Available from TIB Hannover: RO 801(98-18) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman