First-forbidden transitions and stellarβ-decay rates of Zn and Ge isotopes

Abstract

First-forbidden (FF) charge-changing transitions become relatively important for nuclei as their proton number increases. This is because the strength of allowed Gamow-Teller (GT) transitions decreases with increasing Z. The FF transitions play an important role in reducing the half-lives as against those calculated from taking the GT transitions alone into account. In this paper we calculate allowed GT as well as 0 + → 0 − and 0 + → 2 − transitions for neutron-rich Zn and Ge isotopes. Two different pn-QRPA models were used with a schematic separable interaction to calculate GT and FF transitions. Half-lives calculated after inclusion of FF transitions were in excellent agreement with the experimental data. Our calculations were also compared to previous QRPA calculations and were found to be in better agreement with measured data. Stellar β-decay rates were calculated for these nuclei including allowed GT and unique FF transitions for astrophysical applications. 86,88 Ge has a sizeable contribution to the total stellar rate from unique FF transitions.

Double β Decay and the Axial Strength

“…The particle-hole parameter, g ph , of the proton-neutron two-body interaction is usually determined by adjusting the parameter such that the phenomenological or experimental energy of the Gamow-Teller giant resonance is reproduced [20,21]. The spherical pnQRPA has been applied to the description of ββ decays (see e.g., [22][23][24][25]) and it has also been used in β-decay studies (see e.g., [26][27][28]). • MQPM: The microscopic quasiparticle-phonon model (MQPM) describes states of odd-A nuclei starting from the adjacent even-even reference nuclei.…”

“…The shape factor C(w e ) of Equation 22contains complicated combinations of both (universal) kinematic factors and nuclear form factors [26][27][28]. The nuclear form factors can be related to the corresponding NMEs using the impulse approximation [45].…”

Ground-state Nuclear Properties of Neutron-rich Copper Isotopes and Lepton Capture Rates in Stellar Matter

“…The selected values of χ and κ exhibited an inverse mass dependence as suggested in Refs. [18,[35][36][37]. Other variables for the capture rates estimation are the pairing gap (∆ p , ∆ n ), nuclear deformation (β 2 ), Q-values and the Nilsson potential parameters (NPP).…”

First-forbidden $\mathbfβ$-decay rates, energy rates of $β$-delayed neutrons and probability of $β$-delayed neutron emissions for neutron-rich nickel isotopes

“…These values of χ and κ best reproduced the measured half-lives. The same values of χ and κ were also used in another recent calculation of FF β-decay rates of Zn and Ge isotopes [40].…”