Neutron-proton pairing and particle-number fluctuation effects on the moment of inertia of even-even proton-rich nuclei

Abstract

Isovector neutron-proton (np) pairing and particle-number fluctuation effects on the moment of inertia of even- even proton-rich nuclei are investigated. As a first step, an expression of the particle-number projected nuclear moment of inertia is derived within the cranking model. The particle-number symmetry which is broken in the BCS approach is restored using the Sharp-BCS (SBCS) projection method. The obtained expression generalizes the one obtained in the like-particles pairing case. As a second step, the moment of inertia values of deformed even-even proton-rich nuclei such as (N-Z)=0,2,4 are calculated using the single-particle energies and eigen-states of a deformed Woods-Saxon mean-field. It is shown that the np pairing effect is important and clearly depends on (N-Z). Moreover, the particle-number fluctuation effect is very important and is practically independent from (N-Z).