Nuclear structure studies of neutron-rich selenium isotopes

The determination of transition probabilities from level lifetimes of excited nuclear states is of great interest for nuclear structure physics as those give an direct insight to the inner structure of the atomic nucleus. The recoil distance Doppler-shift method is a reliable technique to measure level lifetimes in the picoseconds range. This work addresses the measurement of reduced transition probabilities from level lifetimes of low and intermediate-spin yrast and non-yrast excitations in selenium isotopes on and around the neutron shell-closure at N = 50 within a recoil distance Doppler-shift experiment. The experiment was performed at the Instituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Italy. The Cologne plunger device for deep inelastic scattering was used for the RDDS technique, coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification and combined with the AGATA demonstrator array for the gamma-ray detection and tracking. The experimental results are mainly discussed based on large-scale shell-model calculations, using 56Ni and 78Ni as inert cores.