β-decay of N = 126 isotones for the r-process nucleosynthesis

Abstract

The β-decay properties of nuclei with neutron number N = 126 is investigated in this paper. Two different versions of the proton-neutron quasi particle random phase (pn-QRPA) model were employed to compute β-decay rates and half-lives for the N = 126 isotones. The first set of calculation solves the pn-QRPA equations using the schematic model (SM) approach. The Woods-Saxon potential was employed as a mean-field basis. A spherical shape assigned for each waiting point nuclei throughout all simulations. Both allowed Gamow-Teller (GT) and first-forbidden (FF) transitions were considered in the particle-hole (ph) channel. The second set uses the pn-QRPA model in deformed Nilsson basis to calculate β-decay rates for allowed GT and unique first-forbidden (U1F) transitions under terrestrial and stellar conditions. Our results are in agreement with shell model findings that first-forbidden transitions lead to a considerable decrement in the calculated half-lives of the isotones. Inclusion of the first-forbidden contribution led to a decent agreement of our computed terrestrial β-decay half-lives with measured ones, much better than the previous calculations. The possible implication of the waiting point nuclei on r-process nucleosynthesis is discussed briefly.

Impact of the Brink-Axel hypothesis on unique first-forbidden β-transitions for r-process nuclei*

“…In Eqs. ( 12), (13), and ( 14), and are spin and iso-spin type operators, respectively, and the other symbols ( ), ( ), ( ) and ( ) are defined as…”

“…The observed peaks in the abundance pattern of r-process elements arise due to the deceleration of matter flow at these WPs. Thus, matter assembles at the WP, and nuclei undergo a series of BDs before the r-process recommences [2,[10][11][12][13][14][15][16]. The high temperature (> 1 GK) and high neutron density (> 10 20 g/cm 3 ) conditions associated with the neutron-star to neutron-star collisions [17] and core-collapse supernovae (CCSNe) [11] establish a site for creating the r-process elements.…”

Half-life prediction of some neutron-rich exotic nuclei prior to peak A = 130

“…The quasi-particle random-phase approximation (QRPA) model is one of microscopic models whose computed results, in general, exhibit a good agreement with experimental data. In many earlier studies, QRPA has been successfully implemented, within different approaches, to calculate the nuclear properties of many neutron-rich nuclei, e.g., fully self-consistent QRPA based on Hartree-Fock-Bogoliubov (HFB) theory [23], QRPA method with the density functional (DF) theory [24], fully self-consistent QRPA, based on the spherical relativistic HFB framework [25], the extended QRPA with np pairing considered in the HFB calculations and with the Brükner G-matrix obtained from the CD-Bonn nucleon-nucleon force used for the residual and the pairing interactions [26], deformed QRPA formalism based works [17,[27][28][29][30][31][32][33][34][35], and proton-neutron (p-n)-QRPA model within the deformed Nilsson basis using a separable interaction [36][37][38][39].…”

β-Decay properties of neutron-rich yttrium isotopes

“…Afterwards, this model has been implemented by Nabi et al [25] for weak rates calculations of neutron-rich isotopes of several elements having A 100. In his recent publications, Nabi et al presented β-decay half-lives, GT strength distributions, phase space and stellar weak rates of waiting point nuclei having N = 50, 82 [26,27] and N = 126 [28] by employing the deformed p-n-QRPA model. The β-decay properties of even-even chromium isotopes were earlier studied using the same model [29].…”