With the use of the 58Ni+S~ fusion-evaporation reaction and chemically selective on-line mass separation, the EC//3 + decay of t~ was studied by ?-ray and conversionelectron spectroscopy. In the course of these studies, a new 15.7-s isomeric state of t~ was observed. Reinvestigation of the {/-decays of the two heavier even isotopes of tin, produced in the s 8Ni + 58Ni reaction and mass separated without chemical discrimination, brought new information on the decay of l~ and ~~ The QEc values of 1~ l~ and 1~ were determined to be 4550 +300 keV, 3200+100 keV and -250 <2270 keV, respectively. In the data analysis, the emphasis is put on the identification of the 0+-~ 1 + Gamow-Teller /~ transitions and determination of their strengths. For 1~176 the total Gamow-Teller strengths are measured to be 20% to 30% of that predicted by the single-particle shell model with the inclusion of pairing correlations and core polarization. Predictions of the decay properties of the as yet unobserved ~~ and l~176 are made. 23.40.Hc; 21.10.Dr; 21.10.Pc; 27.60. +j; 29.30.Kv PACS: IntroductionThis paper presents a reinvestigation of the 104, 106,1088n EC/fl+ decays carried out at the GSI mass separator on-line to the UNILAC with the application of nuclear spectroscopy techniques. In the data analysis, the emphasis is put on the identification of the 0+~ 1 + Gamow-Teller (GT) transitions and determination of their strengths. The observation of more than one GT transition in each of the three decays, and the origin of quenching of the summed GT strengths compared to prediction of the extremesingle-particle shell model (ESPSM) are discussed with reference to theoretical studies [1][2][3].The main new results are those obtained for A = 104. Compared to our preceding investigation of the isotope ~~ [4,5] (see also the Leuven results * This work is part of the Ph.D. thesis of G.-E. Rathke[6]), an essential progress in studying its decay properties has been achieved due to the application of a mass-separator ion source [7,8] which allows for a substantial suppression of the isobaric contamination. Also the application of a mini-orange spectrometer [-9] for measuring the spectra of internal-conversion electrons appeared to be a very important addition to our 7-ray studies. As a result, the l~ --+ 1~ decay scheme is constructed with four wellestablished GT transitions.Four GT transitions (two of which were not reported in [10,11]) have also been observed in the 1~ decay. The previous version of the 1~ decay scheme [12, 13] has essentially been confirmed with respect to GT strength. Finally, the results of the present work have been extrapolated to get an estimate of the decay properties for the yet unobserved isotopes 1~and doubly magic l~176

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The new proton-rich nucleus l~ was produced in a 5~ 2p2n)l~ reaction. Its half-life was measured to be 21 + 1 s. From a newly established partial decay scheme, a QEc value of ~,v,,,,a aaa+6so_ 3oo keV was estimated. The resulting mass excess value for 1~ combined with decay energies for e and proton emission, leads to mass excess values for the nuclei ~~ 1~ ll2Xe ' and ~3Cs. These mass values are compared to predictions of mass formulae.

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