A unified view of the first-excited 2⁺ and 3⁻ states of Cd, Sn and Te isotopes

Abstract

Symmetries are known to play an important role in the low-lying level structure of Sn isotopes, mostly in terms of the seniority and generalized seniority schemes. In this paper, we revisit the multi-j generalized seniority approach for the first excited 2⁺ and 3⁻ states in the Cd (Z = 48), Sn (Z = 50) and Te (Z = 52) isotopes, where the Cd and Te isotopes represent two-proton hole and two-proton particle nuclei, thus involving both kind of particles (protons and neutrons) in contrast to Sn isotopes. Interestingly, the approach based on neutron valence space alone is able to explain the B(E2) and B(E3) trends respectively for the 2⁺ and 3⁻ states in all the three Cd, Sn and Te isotopes. The new results on the inverted parabolic behaviour of B(E3) values in Cd and Te isotopes are understood in a manner identical to that of Sn isotopes by using the generalized seniority scheme. No shell quenching is supported by these calculations; hence, the neutron magic numbers, N = 50 and N = 82, remain robust in these isotopic chains. It is quite surprising that the generalized seniority continues to be reasonably successful away from the semi-magic region, thus providing a unifying view of the 2⁺ and 3⁻ states.