β-decay rates--The semi-gross theory--

The β-decay rate of a nucleus is one of the basic data not only in nuclear physics but also in nuclear astrophysics through the study of nucleosynthesis. This rate is obtained from the β-decay strength function, and the semi-gross theory is one of the theories to enable one to estimate the strength function. This theory has been obtained by refining the conventional gross theory to take into account some shell effects of the parent nucleus. In the semi-gross theory, the one-particle energy-levels are assumed to be discrete and non-uniform, and the one-particle strength function depends on the orbital and total angular momenta of the decaying nucleon. Some results, such as half-lives, which are proportional to the inverse of the β-decay rates, and the delayed neutron emission probabilities are given and compared with those from the conventional gross theory and those from a microscopic theory