High spin states and isomeric decays in doubly-odd 208Fr

Abstract

Neutron deficient isotopes of francium ( Z = 87 , N ∼ 121 – 123 ) as excited nuclei were produced in the fusion–evaporation reaction: 197Au( 16O, xn) 213 − x Fr at 100 MeV. The γ rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd 208Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half-lives of the E γ = 194 ( 2 ) keV isomeric transition, known from earlier observations, was measured to be T 1 / 2 = 233 ( 18 ) ns . A second isomeric transition at E γ = 383 ( 2 ) keV and T 1 / 2 = 33 ( 7 ) ns was also found. The measured half-lives were compared with the corresponding single particle estimates, based on the level scheme obtained from the experiment.