High-spin states with seniority v=4,4,6 in 119-126Sn

TL;DR

This paper investigates high-spin states in Sn isotopes 119-126, revealing the breaking of neutron pairs and the maximum angular momentum achievable, marking a first in spherical nuclei.

Contribution

It reports the first observation of maximum angular momentum from broken neutron pairs in spherical nuclei, using gamma-ray spectroscopy of fission fragments.

Findings

Identification of high-spin states above isomers in Sn isotopes

Observation of neutron pair breaking at high excitation energies

First detection of maximum angular momentum in spherical nuclei

Abstract

The 119-126Sn nuclei have been produced as fission fragments in two reactions induced by heavy ions: 12C+238U at 90 MeV bombarding energy, 18O+208Pb at 85 MeV. Their level schemes have been built from gamma rays detected using the Euroball array. High-spin states located above the long-lived isomeric states of the even- and odd-A 120-126Sn nuclei have been identified. Moreover isomeric states lying around 4.5 MeV have been established in 120,122,124,126Sn from the delayed coincidences between the fission fragment detector SAPhIR and the Euroball array. The states located above 3-MeV excitation energy are ascribed to several broken pairs of neutrons occupying the nu h11/2 orbit. The maximum value of angular momentum available in such a high-j shell, i.e. for mid-occupation and the breaking of the three neutron pairs, has been identified. This process is observed for the first time in spherical nuclei.