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Öğe Investigation of Gamow-Teller strength of 186Hg within deformed pn-QRPA(Canadian Science Publishing, 2022) Nabi, Jameel-Un; Ullah, Asim; Kabir, Abdul; Muneem, Abdul; Boyukata, MahmutRecently, the total absorption gamma spectroscopy technique was used to determine the Gamow-Teller (GT) distribution of beta-decay of Hg-186. It was concluded that the best description of the measured data was obtained with dominantly prolate components for both parent Hg-186 and daughter Au-186. Motivated by the recent findings, we investigate the effect of nuclear deformation on the energy distribution of the GT strength of the decay of Hg-186 into Au-186 within the framework of proton-neutron quasiparticle random phase approximation (pn-QRPA) based on the deformed Nilsson potential. To do the needful, we first calculate the energy levels and shape prediction of Hg-186 within the interacting boson model. The computed GT strength distribution satisfied the model-independent Ikeda sum rule 100% (99.98%) for the prolate (oblate) case. Based on the strength distributions, the deformed pn-QRPA model with separable interaction prefers a prolate shape for the ground state of Hg-186 and supports the shape coexistence for this nucleus.Öğe Investigation of Gamow–Teller strength of186 Hg within deformed pn-QRPA(Canadian Science Publishing, 2022) Nabi, Jameel-Un; Ullah, Asim; Kabir, Abdul; Muneem, Abdul; Böyükata, MahmutRecently, the total absorption gamma spectroscopy technique was used to determine the Gamow–Teller (GT) distribution of ?-decay of186 Hg. It was concluded that the best description of the measured data was obtained with dominantly prolate components for both parent186 Hg and daughter186 Au. Motivated by the recent findings, we investigate the effect of nuclear deformation on the energy distribution of the GT strength of the decay of186 Hg into186 Au within the framework of proton– neutron quasiparticle random phase approximation (pn-QRPA) based on the deformed Nilsson potential. To do the needful, we first calculate the energy levels and shape prediction of186 Hg within the interacting boson model. The computed GT strength distribution satisfied the model-independent Ikeda sum rule 100% (99.98%) for the prolate (oblate) case. Based on the strength distributions, the deformed pn-QRPA model with separable interaction prefers a prolate shape for the ground state of186 Hg and supports the shape coexistence for this nucleus. © 2022 The Author(s).Öğe Nuclear structure and weak rates of heavy waiting point nuclei under rp-process conditions(Springer, 2017) Nabi, Jameel-Un; Boyukata, MahmutThe structure and the weak interaction mediated rates of the heavy waiting point (WP) nuclei Zr-80, Mo-84, Ru-88, Pd-92 and Cd-96 along N = Z line were studied within the interacting boson model-1 (IBM-1) and the proton-neutron quasi-particle random phase approximation (pn-QRPA). The energy levels of the N = Z WP nuclei were calculated by fitting the essential parameters of IBM-1 Hamiltonian and their geometric shapes were predicted by plotting potential energy surfaces (PESs). Half-lives, continuum electron capture rates, positron decay rates, electron capture cross sections of WP nuclei, energy rates of beta-delayed protons and their emission probabilities were later calculated using the pn-QRPA. The calculated Gamow-Teller strength distributions were compared with previous calculation. We present positron decay and continuum electron capture rates on these WP nuclei under rp-process conditions using the same model. For the rp-process conditions, the calculated total weak rates are twice the Skyrme HF+BCS+QRPA rates for Zr-80. For remaining nuclei the two calculations compare well. The electron capture rates are significant and compete well with the corresponding positron decay rates under rp-process conditions. The finding of the present study supports that electron capture rates form an integral part of the weak rates under rp-process conditions and has an important role for the nuclear model calculations.Öğe Nuclear structure properties and stellar weak rates for Se-76: Unblocking of the Gamow Teller strength(Elsevier Science Bv, 2017) Nabi, Jameel-Un; Ishfaq, Mavra; Boyukata, Mahmut; Riaz, MuhammadAt finite temperatures (>= 10(7)K), Se-76 is abundant in the core of massive stars and electron capture on Se-76 has a consequential role to play in the dynamics of core-collapse. The present work may be classified into two main categories. In the first phase we study the nuclear structure properties of Se-76 using the interacting boson model-1 (IBM-1). The IBM-1 investigations include the energy levels, B (E2) values and the prediction of the geometry. We performed the extended consistent-Q formalism (ECQF) calculation and later the triaxial formalism calculation (constructed by adding the cubic term to the ECQF). The geometry of Se-76 can be envisioned within the formalism of the potential energy surface based on the classical limit of IBM-1 model. In the second phase, we reconfirm the unblocking of the Gamow Teller (GT) strength in Se-76 (a test case for nuclei having N > 40 and Z < 40). Using the deformed pn-QRPA model we calculate GT transitions, stellar electron capture cross section (within the limit of low momentum transfer) and stellar weak rates for Se-76. The distinguishing feature of our calculation is a state-by-state evaluation of stellar weak rates in a fully microscopic fashion. Results are compared with experimental data and previous calculations. The calculated GT distribution fulfills the Ikeda sum rule. Rates for, beta-delayed neutrons and emission probabilities are also calculated. Our study suggests that at high stellar temperatures and low densities, the beta(+)-decay on Se-76 should not be neglected and needs to be taken into consideration along with electron capture rates for simulation of presupernova evolution of massive stars. (C) 2017 Elsevier B.V. All rights reserved.Öğe Nuclear structure properties and weak interaction rates of even-even Fe isotopes(Elsevier, 2024) Nabi, Jameel-Un; Boyukata, Mahmut; Ullah, Asim; Riaz, MuhammadNuclear structure properties and weak interaction rates of neutron -rich even-even iron (Fe) isotopes (A = 50 - 70) are investigated using the Interacting Boson Model -1 (IBM -1) and the proton-neutron Quasiparticle Random Phase Approximation (pn-QRPA) model. The IBM -1 is used for the calculation of energy levels and the B(E2) values of neutron -rich Fe isotopes. Later their geometry was predicted within the potential energy formalism of the IBM -1 model. Weak interaction rates on neutron -rich nuclei are needed for the modeling and simulation of presupernova evolution of massive stars. In the current study, we investigate the possible effect of nuclear deformation on stellar rates of even-even Fe isotopes. The pn-QRPA model is applied to calculate the weak interaction rates of selected Fe isotopes using three different values of deformation parameter. It is noted that, in general, bigger deformation values led to smaller total strength and larger centroid values of the resulting Gamow-Teller distributions. This later translated to smaller computed weak interaction rates. The current finding warrants further investigation before it may be generalized. The reported stellar rates are up to 4 orders of magnitude smaller than previous calculations and may bear astrophysical significance.Öğe Nuclear structure properties of even-even chromium isotopes and the effect of deformation on calculated electron capture cross sections(ELSEVIER, 2020) Nabi, Jameel-Un; Boyukata, Mahmut; Ullah, Asim; Riaz, MuhammadIn this study, we investigate the role of the nuclear deformation on the calculated electron capture cross section (ECC) of even-even chromium (Cr) isotopes. We first determined the nuclear structure properties of these nuclei within the interacting boson model-1 (IBM-1). The energy spectra and E2 transition probabilities were calculated by fitting the parameters in the model formalism. The analysis of the potential energy surface were also performed to predict the geometric shape of the Cr nuclei by plotting their contour plot in the plane of (beta, gamma ) deformation parameters. Later, we calculated the ECC within the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. In particular we studied how the calculated ECC changed with different values of nuclear deformation parameter. The calculated Gamow-Teller (GT) strength distributions were widely spread among the daughter states. The total GT strength decreased with increasing value of the beta parameter. The computed ECC values, however, increased with increase in the beta value of the Cr isotopes. (c) 2020 Elsevier B.V. All rights reserved.Öğe Re-examination of nuclear structure properties and shape co-existence of nuclei around A ∼ 70(Elsevier, 2024) Nabi, Jameel-Un; Bayram, Tuncay; Böyükata, Mahmut; Ullah, Asim; Hayder, Anes; Naqvi, Syeda ZainabWe re-examine the nuclear structure properties of waiting point nuclei around A similar to 70 using the interacting boson model-1 (IBM-1) and the relativistic mean field (RMF) model. Effective density-dependent meson-exchange functional (DD-ME2) and density-dependent point-coupling functional (DD-PC1) were used for the RMF calculations. We calculated the energy levels, the geometric shapes, binding and separation energies of nucleons and quadrupole deformation parameters (beta 2). The shape co-existence phenomena in A similar to 70 nuclei (Se-68, Se-70, Br-70, Kr-70, Kr-72, Kr-74, Rb-74 and Sr-74) was later investigated. Spherical and deformed shapes of the selected waiting point nuclei were computed using the IBM-1 and RMF models, respectively. The proton-neutron quasiparticle random phase approximation (pn-QRPA) model was used to calculate beta-decay properties (Gamow-Teller strength distributions, beta-decay half-lives and branching ratios) of selected nuclei as a function of beta 2. The results revealed a significant variation in calculated half-lives and Gamow-Teller strength distributions as the shape parameter was changed. The beta 2 computed via DD-ME2 functional resulted in half-lives in best agreement with the measured data.Öğe Re-examination of β-decay in Hg, Pb and PoIsotopes(Iop Publishing Ltd, 2023) Nabi, Jameel-Un; Bayram, Tuncay; Riaz, Muhammad; Ullah, Asim; Hayder, Anes; Şentürk, Şevki; Böyükata, MahmutThis study re-examines the effect of nuclear deformation on the calculated Gamow-Teller (GT) strength distributions of neutron-deficient (Hg178-192, Pb185-194 and Po196-206) nuclei. The nuclear ground state properties and shape parameters were calculated using the Relativistic Mean Field model. Three different density-dependent interactions ((DC)-C-3, DD-ME2 and DD-PC1) were used in the calculation. Estimated shape parameters were later used within the framework of deformed proton-neutron quasi-random phase approximations model, with a separable interaction, to calculate the GT strength distributions, half-lives and branching ratios for these neutron-deficient isotopes. It was concluded that half-lives and GT strength distributions vary considerably with change in shape parameter.Öğe β-Decay half-lives and nuclear structure of exotic proton-rich waiting point nuclei under rp-process conditions(Elsevier, 2016) Nabi, Jameel-Un; Boyukata, MahmutWe investigate even even nuclei in the A similar to 70 mass region within the framework of the proton neutron quasi-particle random phase approximation (pn-QRPA) and the interacting boson model-1 (IBM-1). Our work includes calculation of the energy spectra and the potential energy surfaces V (beta, gamma) of Zn, Ge, Se, Kr and Sr nuclei with the same proton and neutron number, N = Z. The parametrization of the IBM-1 Hamiltonian was performed for the calculation of the energy levels in the ground state bands. Geometric shape of the nuclei was predicted by plotting the potential energy surfaces v(beta, gamma) obtained from the IBM-1 Hamiltonian in the classical limit. The pn-QRPA model was later used to compute half-lives of the neutron-deficient nuclei which were found to be in very good agreement with the measured ones. The pn-QRPA model was also used to calculate the Gamow-Teller strength distributions and was found to be in decent agreement with the measured data. We further calculate the electron capture and positron decay rates for these N = Z waiting point (WP) nuclei in the stellar environment employing the pn-QRPA model. For the rp-process conditions, our total weak rates are within a factor two compared with the Skyrme HF + BCS + QRPA calculation. All calculated electron capture rates are comparable to the competing positron decay rates under rp-process conditions. Our study confirms the finding that electron capture rates form an integral part of the weak rates under rp-process conditions and should not be neglected in the nuclear network calculations. (C) 2016 Elsevier B.V. All rights reserved.
