Nuclear structure studies by means of short-lived isomers at intermediate energies

Abstract

Short-lived (Tl,z about 0.1 to 100~s) isomeric states have been studied for over forty years. Among the methods used for their production thermal neutron induced fission played initially the most, important role (see for example [l]). However, the mass A and atomic number Z of excited fission fragments usually were not directly measured in these experiments limiting the possibility for a search of weakly produced isomers. Presently, the most important, source of spectroscopic information on the structure of short-lived isomers is in-beam spectroscopy applied to fusion-evaporation, deep-inelastic and fission reactions at several MeV per nucleon. Strongly decreasing production cross sections very far from the line of stability put severe constrains on the search for new isomers using in-beam spectroscopy methods. In many cases this difficulty can be overcome using fragmentation-like reactions at several tens or hundreds MeV per nucleon. The study of short-lived isomeric states at intermediate and relativistic energies combines an unambiguous and fast event-by-event identification of nuclei far from stability with