STUDY OF THE BETA-DECAYS OF CA-37 AND CA-36

The beta-delayed proton and gamma-ray emission of Ca-37 and Ca-36 was studied at the projectile fragment separator at GSI Darmstadt. In the Ca-37 study, the beta-delayed gamma decay was observed for the first t ime, and the half-life was redetermined, under essentially background- free conditions, as 181.1 +/- 1.0 ms. The surprisingly high Gamma(gamm a)/gamma(p) values found for proton-unbound states in K-37 drastically reduce former discrepancies between the Gamow-Teller strength values B(GT) measured in the Ca-37 beta decay and those deduced from the Cl-3 7(p,n)Ar-37 mirror reaction, Our data provide evidence, on a level of 1.6 standard deviations, for isospin-mixing of the lowest T = 3/2 leve l in K-37. In the Ca-36 study, a complete beta decay scheme, including the beta-delayed proton emission into the ground and first excited st ates of Ar-35 as well as the beta-delayed gamma decay, was measured fo r the first time, The Ca-36 half-life was remeasured with improved acc uracy to be 102 +/- 2 ms. Our data exclude a 1(+) assignment for two n ear-threshold states in K-36 that could be important resonances in Ar- 35(p,gamma) reactions of astrophysical interest. The B(GT) distributio ns in Ca-37,Ca-36 decays are compared to results obtained from large-s cale sd shell-model calculations, (C) 1997 Elsevier Science B.V.