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

Abstract

The shape of the beta strength function Sbeta and its consequences for various fields of nuclear physics and astrophysics are discussed. Structures in Sbeta - 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 Sbeta 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 Sbeta is decisive also for the cooling by neutrino losses of the interior of degenerate stars. The shape of Sbeta 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.