Abstract
Seniority has proved to be a unique and simple probe to address some of the complex issues underlying nuclear structure of nuclei close to magic numbers. An extension from the concept of seniority in single-j shell to generalized seniority in multi-j shell has recently been provided by us. We have, consequently, established new selection rules for gamma decays and discovered the new seniority isomers decaying via odd electric multipole operators. We have successfully explained the B(EL; L=1,2,3) behavior of various high spin isomers and other excited states. More specifically, we have been able to explain the long-standing puzzle of double hump in the B(E2) values for the first excited 2+ states of even-even Z=50 (Sn) isotopes. In the present paper, we review these generalized seniority calculations with emphasis on even-even Sn isotopes. We first discuss the generalized seniority results for the E1 decaying 13- isomers and E2 decaying 10+, 15- isomers, and then present the cases of first-excited 2+ and 3- states. The generalized seniority proves out to be a reasonably good quantum number. The significance of configuration mixing is found to be true. The calculated results has been validated till high seniority v=4 states and expected to be valid for higher seniority v=6,… states also.
Highlights
The role of pairing interaction is important in understanding the structure of semi-magic nuclei
Seniority scheme, which is based on pairing interaction, was first introduced by Racah [1] to differentiate the states with same values of the orbital angular momentum L, the spin angular momentum S and the total angular momentum J for the LS–coupling approach in the atomic physics
Known in E2 transitions [6,7,8,9], as no favorable conditions exist for the seniority isomers in E1/E3.... transitions within the single-j scheme
Summary
The role of pairing interaction is important in understanding the structure of semi-magic nuclei. Seniority scheme, which is based on pairing interaction, was first introduced by Racah [1] to differentiate the states with same values of the orbital angular momentum L, the spin angular momentum S and the total angular momentum J for the LS–coupling approach in the atomic physics This concept has been embraced in nuclear structure physics [2, 3]. We find and validate these isomers as generalized seniority v=2 isomers by explaining the full B(E2) trend from the suggested configuration mixing. We compare these results with the 15- isomers in Sn isotopes having generalized seniority v=4.
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