Speaker
Description
During the last decades there has been a substantial effort to obtain information about the region around the neutron-rich $^{132}$Sn, the most exotic doubly-magic nucleus presently at reach. The isotope $^{132}$Sn is itself a very interesting case. The simplest excited levels correspond to particle-hole states where a particle is excited across the energy gap of the neutron or proton closed shell. The identification of the multiplets may provide information on the nuclear two-body matrix elements.
In this contribution we report on the fast-timing and gamma spectroscopy of $^{132}$Sn carried out in the framework of the ISOLDE IS610 experiment. The excited states of Sn isotopes were populated in the beta-decay of In isomers, produced in a UC$_x$ target unit equipped with a neutron converter. The In isomers were ionized using the ISOLDE Resonance Ionization Laser Ion Source (RILIS), which for the first time allowed isomer-selective ionization of indium. The measurements took place at the new ISOLDE Decay Station (IDS), equipped with four highly efficient clover-type Ge detectors, along with a compact fast-timing setup consisting of two LaBr$_3$(Ce) detectors and a fast beta detector. The setup incorporated a tape transport system to remove longer-lived activities.
Here we concentrate on the excited structure of $^{132}$Sn, populated in the $\beta$-decay of $^{132}$In, and also, owing to the RILIS isomer selectivity, separately from the $\beta$-n decay of the $^{133}$In 1/2$^-$ isomer and $^{133}$In 9/2$^+$ the ground state. We present results of the analysis that include an expanded level-scheme, which more than a dozen new levels and more than 40 new $\gamma$-transitions. These results are completed with new measurements of the lifetimes of $^{132}$Sn excited states.
