$\beta $-decay Properties of Waiting-point Nuclei for Astrophysical Applications

Nabi, Jameel-Un; Ullah, Asim; Shah, Shivani A.; Daraz, Gul; Ahmad, M. S.

doi:10.5506/aphyspolb.50.1523

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…It is worth noting that no quenching factor was utilized in the present calculation. In the recent past, we have reported β-decay half-lives, GT strength distributions, phase space and stellar weak rates of 13 closed-shell waiting point nuclei (N = 50, 82) employing the deformed pn-QRPA (N) model [30].…”

Section: Resultsmentioning

confidence: 99%

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

Nabi¹,

Çakmak²,

Ullah³

et al. 2021

Phys. Scr.

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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.

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Section: Resultsmentioning

confidence: 99%

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

Nabi¹,

Çakmak²,

Ullah³

et al. 2021

Phys. Scr.

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Farooq,

Nabi,

Shehzadi

2024

Chinese Phys. C

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Key nuclear inputs for the astrophysical r-process simulations are the weak interaction rates. Consequently, the accuracy of these inputs directly affects the reliability of nucleosynthesis modeling. Majority of the stellar rates, used in simulation studies, are calculated invoking the Brink-Axel (BA) hypothesis. The BA hypothesis assumes that the strength functions of all parent excited states are the same as for the ground state, only shifted in energies. However, BA hypothesis has to be tested against microscopically calculated state-by-state rates. In this project we study the impact of the BA hypothesis on calculated stellar β--decay and electron capture rates. Our investigation include both Unique First Forbidden (U1F) and allowed transitions for 106 neutron-rich trans-iron nuclei ([27, 77] ≤ [Z, A] ≤ [82, 208]). The calculations were performed using the deformed proton-neutron quasi-particle random-phase approximation (pn-QRPA) model with a simple plus quadrupole separable and schematic interaction. Waiting-point and several key r-process nuclei lie within the considered mass region of the nuclear chart. We computed electron capture and β--decay rates using two different prescriptions for strength functions. One was based by invoking BA hypothesis and the other was the state-by-state calculation of strength functions, under stellar density and temperature conditions ([10, 1] ≤ [ρYe(g/cm3), T(GK)] ≤ [1011, 30]). Our results show that BA hypothesis invoked U1F β-− rates are overestimated by 4–5 orders of magnitude as compared to microscopic rates. For capture rates, more than 2 orders of magnitude difference was noted when applying BA hypothesis. It was concluded that the BA hypothesis is not a reliable approximation, especially for the β--decay forbidden transitions.

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“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Shehzadi¹,

Nabi²,

Farooq³

2022

Phys. Scr.

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β-decay is amongst the key properties of nuclei required for the modeling of r-process nucleosynthesis. It also governs the flow of abundances among neighboring isotopic chains of high-mass elements. In the present work, a simple proton-neutron quasi particle random phase approximation (pn-QRPA) model has been used for the calculation of β-decay half-lives of Rb, Sr, Y and Zr neutron-rich isotopes. For 97−103Rb, 98−107Sr, 101−109Y and 104−112Zr, where the experimental data were available, the half-life values are reproduced with reasonable accuracy. The same set of model parameters are later used to predict half-lives for few neutron-rich nuclei (104−112Rb, 108−113Sr, 110−114Y and 113−115Zr) where measured data is not available. The pn-QRPA results (including only allowed transitions) are compared with previous calculations (allowed plus forbidden) and exhibit agreement within a factor of 2.0 when compared with the recent available experimental data.

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$\beta $-decay Properties of Waiting-point Nuclei for Astrophysical Applications

Cited by 6 publications

References 33 publications

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

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

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

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

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