Sub-shell closures near doubly-magic 132Sn nucleus

Nuclei near shell closures are perfect candidates to probe the underlying nucleon-nucleon interactions due to relatively simple single-particle structure. Isotopes around the doubly-magic 132Sn nucleus, namely the neutron-rich Cd isotopes and the 138Ce nucleus exhibit structural anomalies. The energy of the first excited 2+ states in neutron-rich Cd isotopes deviates from the expected systematics. It first increases from neutron number, N = 70 to N = 76 and then a flattening of the E(2+) curve occurs at N = 78 and N = 80. To explain this behavior, a quenching of the N = 82 magic shell was proposed which was later ruled out by studying the decay of the 10+ isomeric state in 130Cd. The isomeric-decay studies of odd-mass Cd isotopes, namely 125,127,129Cd revealed the presence of an enhanced proton-neutron interaction resulting in a deviation from the expected systematics. This interesting interplay between the single-particle behavior of the nucleons and the role of proton-neutron interaction in driving the collectivity in a nucleus and its influence on the evolution of nuclear properties around doubly-magic 132Sn will be discussed.

As a post-doc at Yale University, I investigated the predictions of a proton g7/2 sub-shell closure at proton number,Z= 58 in N = 80 isotones. To probe the configurations of the low-lying excited states, a measurement of the g factor of the first excited 21+ in 138Ce was performed. To measure the g factor, the Time-Dependent Recoil Into Vacuum technique (TDRIV) was employed. The experimental setup included Yale plunger device and Gammasphere. Principle of the TDRIV technique and the implications of the extracted g factor on the proposed proton sub-shell closure will be discussed. 

The last part of the talk will deal with my future plans to build a plunger setup at TIFR to be used in conjunction with the INGA array for measuring the nuclear g factors.