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    Allowed and forbidden ?-decay log ft values of neutron-rich Pb and Bi isotopes
    (Springer, 2024) Cakmak, Necla; Nabi, Jameel-Un; Mehmood, Arslan; Ullah, Asim; Tahir, Rubba
    The beta-decay log ft values for Pb210-215 -> Bi210-215 and Bi210-215 -> Po210-215 transitions in the north-east region of Pb-208 nuclei are estimated using the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. The pn-QRPA equations were solved using the schematic model approach. The Woods-Saxon (WS) potential was inserted as a mean-field basis and nuclei were treated as spherical. Allowed Gamow-Teller (GT) and first-forbidden (FF) transitions were investigated in the particle-hole (ph) channel. The calculated log ft values of the allowed GT and FF transitions using the pn-QRPA model with WS potential were found closer to the experimental values. Later we performed calculation of beta-decay rates in stellar environment. Here we solved the random phase approximation (RPA) equations in deformed Nilsson basis, both in the particle-particle (pp) and particle-hole (ph) channels. Allowed beta-decay and unique first-forbidden (U1F) rates were calculated in stellar matter. For certain cases, the calculated U1F contribution was much more than the allowed beta-decay rates under prevailing stellar conditions, in line with previous findings. Increasing temperature of the stellar core affected the allowed GT rates more than the U1F rates.
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    ?-decay of N=126 isotones for the r-process nucleosynthesis
    (Iop Publishing Ltd, 2021) Nabi, Jameel-Un; Cakmak, Necla; Ullah, Asim; Ullah Khan, Asad
    The beta-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 beta-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 beta-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 beta-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.