Influence of 2p-2h configurations onβ-decay rates

Abstract

The effects of the phonon-phonon coupling on the β-decay rates of neutron-rich nuclei are studied in a microscopic model based on Skyrme-type interactions. The approach uses a finite-rank separable approximation (FRSA) of the Skyrme-type particle-hole (p-h) residual interaction. Very large twoquasiparticle spaces can thus be treated. A redistribution of the Gamow-Teller (G-T) strength is found due to the tensor correlations and the 2p − 2h fragmentation of G-T states. As a result, the β − -decay half-lives are decreased significantly. Using the Skyrme interaction SGII together with a volume-type pairing interaction we illustrate this reduction effect by comparing with available experimental data for the Ni isotopes and neutron-rich N = 50 isotones. We give predictions for 76 Fe and 80 Ni in comparison with the case of the doubly-magic nucleus 78 Ni which is an important waiting point in the r-process.

Nuclear response theory for spin-isospin excitations in a relativistic quasiparticle-phonon coupling framework

“…More recently, Ref. [18] studied the influence of phonon-phonon coupling on the description of β-decay rates, based on a Skyrme HF+BCS mean-field and a residual Landau-Migdal force. Finally, a lot of progress has been made in the past few years towards the development of self-consistent approaches based on the particlevibration coupling (PVC) model.…”

Delayed Multi-Neutron Emission in Very Neutron-Rich Nuclei

“…The estimated Pxn-values should be sensitive to the GT strength fragmentation and redistribution near-thresholds. The quasiparticlephonon coupling is known to be extremely important for description of the GT strength distribution, half-lives [1,19] and Pxn-values [20,21]. Our calculation gives P1n=5.5% (17.8), P2n=86.8% (56.5), P3n=9.4% (6.1), P4n=0.01% (0.01).…”

Multi-neutron emission of Cd isotopes

“…The separable form of the residual interaction is the practical advantage of the quasiparticle phonon model (QPM) [20] which allows one to perform the calculations in large configurational spaces [15,20,21]. The finite rank separable approximation (FRSA) for the QRPA with Skyrme interactions [22,23] has been invented to describe charge-exchange excitation modes [24,25].…”