Global description ofβ−decay in even-even nuclei with the axially-deformed Skyrme finite-amplitude method

Abstract

We use the finite amplitude method for computing charge-changing Skyrme-QRPA transition strengths in axially-deformed nuclei together with a modern Skyrme energy-density functional to fit several previously unconstrained parameters in the charge-changing time-odd part of the functional. With the modified functional we then calculate rates of beta-minus decay for all medium-mass and heavy even-even nuclei between the valley of stability and the neutron drip line. We fit the Skyrme parameters to a limited set of beta-decay rates, a set of Gamow-Teller resonance energies, and a set of spin-dipole resonance energies, in both spherical and deformed nuclei. Comparison to available experimental beta-decay rates shows agreement at roughly the same level as in other global QRPA calculations. We estimate the uncertainty in our rates all the way to the neutron drip line through a construction that extrapolates the errors of known beta-decay rates in nuclei with intermediate Q values to less stable isotopes with higher Q values.

Finite amplitude method applied to the giant dipole resonance in heavy rare-earth nuclei

“…To date, FAM has been applied also to the axially symmetric coordinate-space HFB solver [30] and to the relativistic mean-field framework [31,32]. Various applications of the FAM include descriptions of giant and pygmy dipole excitations [33,34], efficient computation of the QRPA matrix elements [35], and evaluation of beta-decay rates, including the proton-neutron pairing correlations [36,37]. The contour integration technique of FAM-QRPA was developed to describe individual QRPA modes [38] and for a fast calculation of the energy-weighted sum rules [39].…”

Pairing Nambu-Goldstone Modes within Nuclear Density Functional Theory

“…Moreover, since ground-state configurations of odd-A nuclei internally break the time-reversal symmetry, poorly known timeodd terms of the EDF must be considered. Although some of the time-odd functionals are constrained through the local gauge invariance of the EDF [29], the optimization of the unconstrained time-odd coupling constants has barely started [30]. Consequently, the precision of the nuclear EDF for odd-A systems is not as good as that for even-even systems.…”

Multi-neutron emission of Cd isotopes

“…The theoretical analysis has been done within the microscopic-macroscopic finite-range droplet model (FRDM+QRPA) [26,31], the continuum QRPA approach with the Fayans EDF (DF3+cQRPA) [10,11,32,33]. Recently, the proton-neutron relativistic QRPA (pn-RQRPA) [34] and the finite-amplitude method (FAM) [35] calculations have appeared. In general, the microscopic approaches [11,34,35] described the half-lives and total probabilities of the βxn emission better than the global approach [36] commonly used for astrophysical r-process modeling.…”