Global description of β− decay with the axially deformed Skyrme finite-amplitude method: Extension to odd-mass and odd-odd nuclei

Abstract

We use the finite amplitude method (FAM), an efficient implementation of the quasiparticle random phase approximation, to compute beta-decay rates with Skyrme energy-density functionals for 3983 nuclei, essentially all the medium-mass and heavy isotopes on the neutron rich side of stability. We employ an extension of the FAM that treats odd-mass and odd-odd nuclear ground states in the equal filling approximation. Our rates are in reasonable agreement both with experimental data where available and with rates from other global calculations.

Competition between allowed and first-forbidden β decays and the r-process

“…Since shell-model calculations are not feasible far from closed shells, all global calculations use mean field approaches, and all recent ones include first-forbidden decays. These are based on FRDM+QRPA [6], KTUY5 [7], DF3+cQRPA [8], FRDM+QRPA [9], RHB+RQRPA [2] and FAM [1] methods, and their results are compared with the experimental value in table 1. From a similar, but much higher yield experiment it was established that 207 Hg (Q β =4.55 MeV [4]) also decays predominantly (several observed states have no firm parity assignment) via FF β decays [10].…”

“…Since heavy (A>150) r-process path nuclei still cannot be produced in laboratories, yield calculations have to rely on β decay half-lives predicted by theoretical calculations. In contrast to lighter mass regions, around neutron-number N=126 there is competition between (parity conserving) allowed and (parity changing) first-forbidden β decays [1,2]. First-forbidden (FF) transitions can be dominant, with profound implications on their half-lives and therefore on the r-process, specifically on the third r-process peak at A∼195 [3].…”

Beyond-mean-field calculations of allowed and first-forbidden β− decays of r-process waiting-point nuclei

“…Currently, three global sets of β-decay rates are available, which have been calculated within different QRPA frameworks. The earlier set based on the finite range droplet model and schematic interaction [1], and two more recent self-consistent and fully microscopic QRPA calculations based on a relativistic Langrangian [2] and non-relativistic Skyrme functional [3]. Overall the predictions of these three QRPA frameworks disagree to some degree, in particular on the contribution of the FF transitions in different mass regions, and on the order of magnitude of the total half-lives above N > 126 which are predicted to be substantially lower by Ref.…”

Global calculation of two-neutrino double-$β$ decay within the finite amplitude method in nuclear density functional theory

“…The proton-neutron version of the FAM (pnFAM) was developed and implemented in Ref. [18] in order to calculate β-decay rates and Gamow-Teller strength distributions [19,20]. Because of its efficiency, it was used in Ref.…”