Spectroscopy of 34,35Si by β decay: sd-fp shell gap and single-particle states

Abstract

The 34,35Al β decays have been studied at the CERN online mass separator ISOLDE by β-γ, β-γ-γ, and β-n-γ measurements in order to corroborate the low-level description of 34Si and to obtain the first information on the level structure of the N= 21 isotope 35Si. Earlier observed γ lines in 34Al decay were confirmed and new γ transitions following both β decay and β-delayed neutron emission have been established. The first level scheme of 35Si includes three excited states at 910, 974, and 2168 keV. Indication is found for Jπ = (3/2)- and (3/2)+ for the first two excited states, respectively. Beta-decay half-life of T1/2 = 38.6(4) ms and β-delayed neutron branching value Pn = 41(13)% were measured unambiguously. The significance of the single-particle energy determination at N= 21, Z= 14 for assessing the effective interaction in sd-fp shell-model calculations is discussed and illustrated by predictions for different neutron-rich isotopes.