Nuclear electron captures and supernova explosion

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(1)The weak interaction rates in stellar matter are calculated for the sd shell nuclei in the full she II model configurations using the effective interaction of Wildenthal, taking into account the recent extensive compilations of experimental energy levels and Gamow-Teller beta deacay rates. Based on comparisons between the present calculation and that of Fuller, l'owler and Newman(FFN), it is pointed out that correct treatment of nuclear structure effect is decisive in order to get the reliable weak interaction rates in stellar matter. The weak rates are tabulated for the same grid points of density and temperature as those of FFN.(2)A comprehensive representation is presented of a generalized form of the protonneutron'quasiparticle RPA model, originally introduced by lialbleib and Sorensen almost thirty years ago. The model uses separable Gamow-Teller fores, including, in addition to the particle-hole force, of the former model, the particle-particle force, which is of deciive importance for beta^+ decay and beta beta decay. The above model has further been extended to the treatment of odd-odd nuclei. Ali extension is also made to transitions from nuclear excited states. This is essential for calculations of nuclear weak transition rates in the high-temperature interior of massive stars. Complementing the discussion of lialbleib and Sorensen on the particle-hole force, the structure of the RPA dispersion relation is discussed with emphasis on effects of the paricle-particle force.