Within the context of the proton-neutron quasi-particle random phase approximation(pn-QRPA)model and TALYS v1.96 code,the radiative capture(^(99)Tc(n,γ)^(100)Tc)and stellar weak interaction(^(99)Tc→^(99)Ru+e^(−)+ν_...Within the context of the proton-neutron quasi-particle random phase approximation(pn-QRPA)model and TALYS v1.96 code,the radiative capture(^(99)Tc(n,γ)^(100)Tc)and stellar weak interaction(^(99)Tc→^(99)Ru+e^(−)+ν_(e))rates were computed during thermal pulses operating in asymptotic giant branch stars.The Maxwellian average cross-section(MACS)and neutron capture rates for the^(99)Tc(n,γ)^(100)Tc process are analyzed within the context of statistical code TALYS v1.96.The effect of nuclear level density(NLD)andγ-strength functions on MACS and neutron capture rates has been examined.The model-based computations for MACS provided an insightful contrast to prior investigated findings.The sensitivity of stellar weak interaction rates to different densities and temperatures is investigated using the pn-QRPA model.The impact of thermally populated excited states on electron emission(β^(−))rates in^(99)Tc is extensively examined.Additionally,a comparison is made between the study of the stellarβ^(−)decay rates and the thermal neutron capture rates.It is found that at T_(9)=0.26 the thermal neutron capture rates(λ_((n,γ)))and the temperature dependent stellarβ^(−)decay rates( λ_(β-))cross each other.However,at higher temperatures,theλ(n,γ)are found to be higher than λ_(β-).展开更多
Theβ-decay properties of^(67-80)As nuclei have been investigated within the framework of the proton-neutron quasi-particle random phase approximation(pn-QRPA)model.The nuclear deformation obtained from the finite ran...Theβ-decay properties of^(67-80)As nuclei have been investigated within the framework of the proton-neutron quasi-particle random phase approximation(pn-QRPA)model.The nuclear deformation obtained from the finite range droplet model is used as an input parameter in the pn-QRPA model for the analysis ofβ-decay properties including Gamow-Teller strength distributions,log ft,β-decay half-lives and stellarβ^(±)decay rates.The predicted log ft values were fairly consistent with the observed data.The computedβ-decay half-lives matched the measured values by a factor of 10.The stellar rates were compared with the shell model outcomes.At high densities and temperatures,theβ^(+)and electron capture rates had a finite contribution.However,theβ^(-)and positron capture rates are only significant at high temperatures and low densities.The pn-QRPA rates outperformed the shell model rates by a factor of 22 or more.展开更多
The nuclear ground state properties of even-even^(106-120)Zr nuclei have been investigated within the framework of the relativistic mean field(RMF)approach.The RMF model with density-dependent DDME2 and DDPC1 interact...The nuclear ground state properties of even-even^(106-120)Zr nuclei have been investigated within the framework of the relativistic mean field(RMF)approach.The RMF model with density-dependent DDME2 and DDPC1 interactions is utilized for the calculation of potential energy curves,the nuclear ground-state deformation parameters(β_(2)),neutron separation energies(S_(n)and S_(2n))and neutron skin thickness(rnp)of selected Zr isotopes.Later,theβ-decay properties of Zr isotopes were studied using the proton-neutron quasi-particle random phase approximation(pn-QRPA)model.These include Gamow-Teller strength distributions,β-decay half-lives and stellar electron emission/positron capture rates.Theβ2 values computed from the RMF model were employed in the pn-QRPA model as an input parameter for the calculations ofβ-decay properties for even-even 106-120Zr nuclei.The stellar rates were computed using the pn-QRPA framework with three different types of deformation parameters.Only at high temperature(T_(9)≥2)and low density(ρYe≤10^(7)g cm^(−3))values,the sum of electron emission and positron capture rates has a sizeable contribution(with positive exponents)to the stellar rates.展开更多
Radiative capture p+^(9)Be→^(10)B+γ at energies bearing astrophysical importance is a key process for the spectroscopic study of ^(10)B.In this work,we consider the radiative capture cross-section for the ^(9)Be(p,...Radiative capture p+^(9)Be→^(10)B+γ at energies bearing astrophysical importance is a key process for the spectroscopic study of ^(10)B.In this work,we consider the radiative capture cross-section for the ^(9)Be(p,γ)^(10)B within the framework of the potential model and the R-matrix method for the multi-entrance channel cases.In certain cases,when the potential fails,therefore,the R-matrix approach is better to use for the description of partial components of the cross-section that have sharp or broad resonances.For all possible electric and magnetic dipole transitions,partial components of the astrophysical S-factor are computed.The computed value of the total S-factor at zero energy is consistent with the reported results.展开更多
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.The majority of the ...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.The majority of the stellar rates,used in simulation studies are calculated by 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,the 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 stellarβ^(-)-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 quasiparticle 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 andβ^(-)-decay rates using two different prescriptions for strength functions.One was based on invoking the BA hypothesis and the other was the state-by-state calculation of strength functions,under stellar density and temperature conditions([10,1]≤[ρYe(g/cm^(3)),T(GK)]≤[10^(11),30]).Our results show that the BA hypothesis invoked U1Fβ^(-)rates are overestimated by 4–5 orders of magnitude as compared to microscopic rates.For capture rates,more than two orders of magnitude differences were noted when applying the BA hypothesis.It was concluded that the BA hypothesis is not a reliable approximation,especially forβ^(-)-decay forbidden transitions.展开更多
The CNO cycle is the main source of energy in stars more massive than our Sun.This process defines the energy production,the duration of which can be used to determine the lifetime of massive stars.The cycle is an imp...The CNO cycle is the main source of energy in stars more massive than our Sun.This process defines the energy production,the duration of which can be used to determine the lifetime of massive stars.The cycle is an important tool for determining the age of globular clusters.Radiative proton capture via p+^(14)N→^(15)O+γ,at energies of astrophysical interest,is an important process in the CNO cycle.In this project,we apply a potential model to describe both non-resonant and resonant reactions in the channels where radiative capture occurs through electric E1 transitions.We employed the R-matrix method to describe the ongoing reactions via M1 resonant transitions,when it was not possible to correctly reproduce the experimental data using the potential model.The partial components of the astrophysical S-factor are calculated for all possible electric and magnetic dipole transitions in ^(15)O.The linear extrapolated S-factor at zero energy(S(0))agrees well with earlier reported values for all transition types considered in this work.Based on the value of the total astrophysical S-factor,depending on the collision energy,we calculate the nuclear reaction rates for p+^(14)N→^(15)O+γ.The computed rates agree well with the results reported in the NACRE II Collaboration and most recent existing measurements.展开更多
The neutron capture rates and temperature dependent stellar beta decay rates of Mo isotopes are investigated within the framework of the statistical code TALYS v1.96 and the proton neutron quasi particle random phase ...The neutron capture rates and temperature dependent stellar beta decay rates of Mo isotopes are investigated within the framework of the statistical code TALYS v1.96 and the proton neutron quasi particle random phase approximation(pn-QRPA)model.The Maxwellian average cross-section(MACS)and neutron capture rates for the^(95-98)Mo(n,γ)^(96-99)Mo radiative capture process are analyzed within the framework of the statistical code TALYS v1.96 based on the phenomenological nuclear level density model and gamma strength functions.The present model-based computations for the MACS are comparable to the existing measured data.The sensitivity of stellar weak interaction rates to various densities and temperatures is investigated within the framework of the pn-QRPA model.Particular attention is paid to the impact of thermally filled excited states in the decaying nuclei(^(95-98)Mo)on electron emission and positron capture rates.Furthermore,we compare the neutron capture rates and stellar beta decay rates.It is found that neutron capture rates are higher than stellar beta decay rates at both lower and higher temperatures.展开更多
基金the financial support of the Higher Education Commission Pakistan through project number 20-15394/NRPU/R&D/HEC/2021.
文摘Within the context of the proton-neutron quasi-particle random phase approximation(pn-QRPA)model and TALYS v1.96 code,the radiative capture(^(99)Tc(n,γ)^(100)Tc)and stellar weak interaction(^(99)Tc→^(99)Ru+e^(−)+ν_(e))rates were computed during thermal pulses operating in asymptotic giant branch stars.The Maxwellian average cross-section(MACS)and neutron capture rates for the^(99)Tc(n,γ)^(100)Tc process are analyzed within the context of statistical code TALYS v1.96.The effect of nuclear level density(NLD)andγ-strength functions on MACS and neutron capture rates has been examined.The model-based computations for MACS provided an insightful contrast to prior investigated findings.The sensitivity of stellar weak interaction rates to different densities and temperatures is investigated using the pn-QRPA model.The impact of thermally populated excited states on electron emission(β^(−))rates in^(99)Tc is extensively examined.Additionally,a comparison is made between the study of the stellarβ^(−)decay rates and the thermal neutron capture rates.It is found that at T_(9)=0.26 the thermal neutron capture rates(λ_((n,γ)))and the temperature dependent stellarβ^(−)decay rates( λ_(β-))cross each other.However,at higher temperatures,theλ(n,γ)are found to be higher than λ_(β-).
基金funded by Taif University,Saudi Arabia,Project No.(TU-DSPP-2024-33)。
文摘Theβ-decay properties of^(67-80)As nuclei have been investigated within the framework of the proton-neutron quasi-particle random phase approximation(pn-QRPA)model.The nuclear deformation obtained from the finite range droplet model is used as an input parameter in the pn-QRPA model for the analysis ofβ-decay properties including Gamow-Teller strength distributions,log ft,β-decay half-lives and stellarβ^(±)decay rates.The predicted log ft values were fairly consistent with the observed data.The computedβ-decay half-lives matched the measured values by a factor of 10.The stellar rates were compared with the shell model outcomes.At high densities and temperatures,theβ^(+)and electron capture rates had a finite contribution.However,theβ^(-)and positron capture rates are only significant at high temperatures and low densities.The pn-QRPA rates outperformed the shell model rates by a factor of 22 or more.
基金funded by Taif University,Saudi Arabia,Project No.(TU-DSPP-2024-33).
文摘The nuclear ground state properties of even-even^(106-120)Zr nuclei have been investigated within the framework of the relativistic mean field(RMF)approach.The RMF model with density-dependent DDME2 and DDPC1 interactions is utilized for the calculation of potential energy curves,the nuclear ground-state deformation parameters(β_(2)),neutron separation energies(S_(n)and S_(2n))and neutron skin thickness(rnp)of selected Zr isotopes.Later,theβ-decay properties of Zr isotopes were studied using the proton-neutron quasi-particle random phase approximation(pn-QRPA)model.These include Gamow-Teller strength distributions,β-decay half-lives and stellar electron emission/positron capture rates.Theβ2 values computed from the RMF model were employed in the pn-QRPA model as an input parameter for the calculations ofβ-decay properties for even-even 106-120Zr nuclei.The stellar rates were computed using the pn-QRPA framework with three different types of deformation parameters.Only at high temperature(T_(9)≥2)and low density(ρYe≤10^(7)g cm^(−3))values,the sum of electron emission and positron capture rates has a sizeable contribution(with positive exponents)to the stellar rates.
文摘Radiative capture p+^(9)Be→^(10)B+γ at energies bearing astrophysical importance is a key process for the spectroscopic study of ^(10)B.In this work,we consider the radiative capture cross-section for the ^(9)Be(p,γ)^(10)B within the framework of the potential model and the R-matrix method for the multi-entrance channel cases.In certain cases,when the potential fails,therefore,the R-matrix approach is better to use for the description of partial components of the cross-section that have sharp or broad resonances.For all possible electric and magnetic dipole transitions,partial components of the astrophysical S-factor are computed.The computed value of the total S-factor at zero energy is consistent with the reported results.
基金supported by the Higher Education Commission Pakistan through Project (0-15394/NRPU/R&D/HEC/2021)。
文摘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.The majority of the stellar rates,used in simulation studies are calculated by 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,the 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 stellarβ^(-)-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 quasiparticle 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 andβ^(-)-decay rates using two different prescriptions for strength functions.One was based on invoking the BA hypothesis and the other was the state-by-state calculation of strength functions,under stellar density and temperature conditions([10,1]≤[ρYe(g/cm^(3)),T(GK)]≤[10^(11),30]).Our results show that the BA hypothesis invoked U1Fβ^(-)rates are overestimated by 4–5 orders of magnitude as compared to microscopic rates.For capture rates,more than two orders of magnitude differences were noted when applying the BA hypothesis.It was concluded that the BA hypothesis is not a reliable approximation,especially forβ^(-)-decay forbidden transitions.
文摘The CNO cycle is the main source of energy in stars more massive than our Sun.This process defines the energy production,the duration of which can be used to determine the lifetime of massive stars.The cycle is an important tool for determining the age of globular clusters.Radiative proton capture via p+^(14)N→^(15)O+γ,at energies of astrophysical interest,is an important process in the CNO cycle.In this project,we apply a potential model to describe both non-resonant and resonant reactions in the channels where radiative capture occurs through electric E1 transitions.We employed the R-matrix method to describe the ongoing reactions via M1 resonant transitions,when it was not possible to correctly reproduce the experimental data using the potential model.The partial components of the astrophysical S-factor are calculated for all possible electric and magnetic dipole transitions in ^(15)O.The linear extrapolated S-factor at zero energy(S(0))agrees well with earlier reported values for all transition types considered in this work.Based on the value of the total astrophysical S-factor,depending on the collision energy,we calculate the nuclear reaction rates for p+^(14)N→^(15)O+γ.The computed rates agree well with the results reported in the NACRE II Collaboration and most recent existing measurements.
文摘The neutron capture rates and temperature dependent stellar beta decay rates of Mo isotopes are investigated within the framework of the statistical code TALYS v1.96 and the proton neutron quasi particle random phase approximation(pn-QRPA)model.The Maxwellian average cross-section(MACS)and neutron capture rates for the^(95-98)Mo(n,γ)^(96-99)Mo radiative capture process are analyzed within the framework of the statistical code TALYS v1.96 based on the phenomenological nuclear level density model and gamma strength functions.The present model-based computations for the MACS are comparable to the existing measured data.The sensitivity of stellar weak interaction rates to various densities and temperatures is investigated within the framework of the pn-QRPA model.Particular attention is paid to the impact of thermally filled excited states in the decaying nuclei(^(95-98)Mo)on electron emission and positron capture rates.Furthermore,we compare the neutron capture rates and stellar beta decay rates.It is found that neutron capture rates are higher than stellar beta decay rates at both lower and higher temperatures.
