Nuclear pairing reduction due to rotation and blocking

Abstract

Nuclear pairing gaps of normally deformed and superdeformed nuclei are investigated using the particle-number conserving (PNC) formalism for the cranked shell model, in which the blocking effects are treated exactly. Both rotational frequency $\omega$-dependence and seniority (number of unpaired particles) $\nu$-dependence of the pairing gap $\tilde{\Delta }$ are investigated. For the ground-state bands of even-even nuclei, PNC calculations show that in general $\tilde{\Delta }$ decreases with increasing $\omega$, but the $\omega$-dependence is much weaker than that calculated by the number-projected Hartree-Fock-Bogolyubov approach. For the multiquasiparticle bands (seniority $\nu >2$), the pairing gaps keep almost $\omega$-independent. As a function of the seniority $\nu$, the bandhead pairing gaps $\tilde{\Delta }(\nu ,\omega =0)$ decrease slowly with increasing $\nu$. Even for the highest seniority $\nu$ bands identified so far, $\tilde{\Delta }(\nu ,\omega =0)$ remains greater than 70% of $\tilde{\Delta }(\nu =0,\omega =0)$.

Comments: 15 pages, 5 figures