Structures in the beta strength function and consequences for nuclear physics and astrophysics

Abstract

The shape of the beta strength function S_beta and its consequences for various fields of nuclear physics and astrophysics are discussed. Structures in S_{beta -} are shown to arise mainly from back-spin-flip, core-polarised and spin-flip states and from the second E1(-1, -1, -1) mode in beta ^- decay and from spin-flip states and the E1(+1, +1, +1) mode in beta ⁺ decay. These structures in S_beta are not taken into account in any of the presently existing calculations for the synthesis of heavy elements. It is shown that they strongly affect beta -decay half-lives, beta -delayed particle emission, beta -delayed fission, and in this way all calculations for synthesis of heavy and superheavy nuclides by astrophysical processes like the r or n process and by thermonuclear explosions. The shape of S_beta is decisive also for the cooling by neutrino losses of the interior of degenerate stars. The shape of S_beta has to be known for determinations of fission barrier heights from beta-delayed fission branching ratios. Its knowledge is further important for optimising the emergency cooling systems of nuclear reactors and for the control of fast breeder reactors.