# Gamma spectroscopy of neutron-rich isotopes in the $A = 100$ region produced in fission induced by cold neutrons with the new FIPPS array.

Iskra L.W., Leoni S., Fornal B., Bottoni S., Cieplicka-Orynczak N., Jentschel M., Kandzia F., Kim Y.H., Köster U., Michelagnoli C., Mutti P., Porzio C., Ruiz-Martinez E.

Comunicazione
I - Fisica nucleare e subnucleare
Aula Palazzo dell'Emiciclo - Sala Ipogea - Mercoledì 25 h 10:00 - 13:00
The phenomenon of sudden onset of the deformation in nuclei around $A=100, N=60$ is considered the most dramatic shape change in the nuclear chart. We have investigated the structures of the neutron-rich Y isotopes produced in the fission of ${}^{235}U$ active target induced by cold neutrons from the reactor at ILL. The level schemes of ${}^{92,94,96}Y$ nuclei have been established based on gamma-ray coincidences measured with the highly efficient HPGe array called FIPPS. The new results suggest that deformed structures appear just after the subshell closure at $N=56$ and evolve smoothly when passing through $N=57-59$ isotopes, to become the ground state structure at $N=60$.