Complex configuration effects on β-decay rates

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. Making use of the finite rank separable approach for the quasiparticle random phase approximation enables one to perform nuclear structure calculations in very large configurational spaces. The inclusion of the tensor correlations and the 2p – 2h configurations results in a redistribution of the Gamow- Teller strength and a consequent reduction of the β-decay half-life. Such an effect is discussed for some neutron-rich N = 82 isotones below the doubly magic nucleus ¹³²Sn. The calculations are performed by using the SGII Skyrme interactions with the tensor terms in the particle- hole channel and the surface-peaked interaction in the particle-particle channel. Predictions are given for ¹²⁶Ru and ¹²⁸Pd in comparison to ¹³⁰Cd which is the r-process waiting-point nucleus.