scholarly journals β-DECAY OF KEY TITANIUM ISOTOPES IN STELLAR ENVIRONMENT

2011 ◽  
Vol 20 (03) ◽  
pp. 705-719
Author(s):  
JAMEEL-UN NABI ◽  
IRGAZIEV BAKHADIR
Keyword(s):  
Electron Capture ◽  
Large Scale ◽  
Massive Stars ◽  
Random Phase ◽  
Neutrino Energy ◽  
Decay Rates ◽  
Β Decay ◽  
Quasiparticle Random Phase Approximation ◽  
Stellar Temperatures ◽  
Titanium Isotopes

Amongst iron regime nuclei, β-decay rates on titanium isotopes are considered to be important during the late phases of evolution of massive stars. The key β-decay isotopes during presupernova evolution were searched from available literature and a microscopic calculation of the decay rates were performed using the proton–neutron quasiparticle random phase approximation (pn-QRPA) theory. As per earlier simulation results, electron capture and β-decay on certain isotopes of titanium are considered to be important for the presupernova evolution of massive stars. Earlier the stellar electron capture rates and neutrino energy loss rates due to relevant titanium isotopes were presented. In this paper we finally present the β-decay rates of key titanium isotopes in stellar environment. The results are also compared against previous calculations. The pn-QRPA β-decay rates are bigger at high stellar temperatures and smaller at high stellar densities compared to the large scale shell model results. This study can prove useful for the core-collapse simulators.

scholarly journals NEUTRINO AND ANTINEUTRINO ENERGY LOSS RATES IN MASSIVE STARS DUE TO ISOTOPES OF TITANIUM

2010 ◽  
Vol 19 (01) ◽  
pp. 63-77 ◽  
Author(s):  
JAMEEL-UN NABI
Keyword(s):  
Energy Loss ◽  
Large Scale ◽  
Massive Stars ◽  
Random Phase ◽  
Accurate Estimate ◽  
Neutrino Energy ◽  
Decay Rates ◽  
Quasiparticle Random Phase Approximation ◽  
Loss Rates ◽  
Titanium Isotopes

Weak interaction rates on titanium isotopes are important during the late phases of evolution of massive stars. A search was made for key titanium isotopes from available literature and a microscopic calculation of weak rates of these nuclei were performed using the proton-neutron quasiparticle random phase approximation (pn-QRPA) theory. Earlier the author presented the stellar electron capture rates on titanium isotopes. In this paper I present the neutrino and antineutrino energy loss rates due to capture and decay rates on isotopes of titanium in stellar environment. Accurate estimate of neutrino energy loss rates are needed for the study of the late stages of the stellar evolution, in particular for cooling of neutron stars and white dwarfs. The results are also compared against previous calculations. At high stellar temperatures the calculated neutrino and antineutrino energy loss rates are bigger by more than two orders of magnitude as compared to the large scale shell model results and favor stellar cores with lower entropies. This study can prove useful for core-collapse simulators.

scholarly journals Electron-capture modes with realistic nuclear structure calculations

2019 ◽  
Vol 21 ◽  
pp. 4
Author(s):  
P. G. Giannaka ◽  
T. S. Kosmas
Keyword(s):  
Electron Capture ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Random Phase ◽  
Point Of View ◽  
Electron Neutrino ◽  
Β Decay ◽  
Decay Modes ◽  
Theory Point ◽  
Nuclear Structure Calculations

Nuclear electron capture posses prominent position among other weak interaction processes occuring in explosive nucleosynthesis. In particular, this process plays important role in the core-colapse of massive stars by modifying the electron to baryon ratio Ye. From a nuclear theory point of view, such processes may be studied by using the same nuclear methods (e.g. the quasi-particle random phase approximation, QRPA), employed in the present work with these used for the one-body charge changing nuclear reactions (β-decay modes, charged-current electron-neutrino absorption by nuclei, etc). In this work we calculate e−-capture cross sections on 56Fe using two different approaches. At first, original cross section calculations are perfored by using the pn-QRPA method considering all the accessible transitions of the final nucleus 56Mn. Secondly, we evaluate the Gamow-Teller strength distributions and obtain the cross sections at the limit of zero-momentum transfer. The agreement between the two methods is very good.

Beta-decay half-lives of the extremely neutron-rich nuclei in the closed-shell N = 50, 82, 126 groups

2021 ◽  
Author(s):  
Nguyen Kim Uyen ◽  
Kyung Yuk Chae ◽  
NgocDuy Nguyen ◽  
DuyLy Nguyen
Keyword(s):  
Half Life ◽  
Random Phase ◽  
Closed Shell ◽  
Decay Rates ◽  
Magic Numbers ◽  
Β Decay ◽  
R Process ◽  
Neutron Rich Isotopes ◽  
Semi Empirical ◽  
The Impact

Abstract The β--decay half-lives of extremely neutron-rich nuclei are important for understanding nucleosynthesis in the r-process. However, most of their half-lives are unknown or very uncertain, leading to the need for reliable calculations. In this study, we updated the coefficients in recent semi-empirical formulae using the newly updated mass (AME2020) and half-life (NUBASE2020) databases to improve the accuracy of the half-life prediction. In particular, we developed a new empirical model for better calculations of the β--decay half-lives of isotopes ranging in Z = 10 – 80 and N = 15-130. We examined the β--decay half-lives of the extremely neutron-rich isotopes at and around the neutron magic numbers of N = 50, 82, and 126 using either five different semi-empirical models or finite-range droplet model and quasi-particle random phase approximation (FRDM+QRPA) method. The β--decay rates derived from the estimated half-lives were used in calculations to evaluate the impact of the half-life uncertainties of the investigated nuclei on the abundance of the r-process. The results show that the half-lives mostly range in 0.001 < T1/2 < 100 s for the nuclei with a ratio of N/Z < 1.9; however, they differ significantly for those with the ratio of N/Z > 1.9. The half-life differences among the models were found to range from a few factors (for N/Z < 1.9 nuclei) to four orders of magnitude (for N/Z > 1.9). These discrepancies lead to a large uncertainty, which is up to four orders of magnitude, in the r-process abundance of isotopes. We also found that the multiple-reflection time-of-flight (MR-TOF) technique is preferable for precise mass measurements because its measuring timescale applies to the half-lives of the investigated nuclei. Finally, the results of this study are useful for studies on the β-decay of unstable isotopes and astrophysical simulations.

scholarly journals Electron Capture Cross Sections for Stellar Nucleosynthesis

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
P. G. Giannaka ◽  
T. S. Kosmas
Keyword(s):  
Electron Capture ◽  
Cross Sections ◽  
Random Phase ◽  
Model Space ◽  
Boltzmann Distribution ◽  
Capture Cross ◽  
Quasiparticle Random Phase Approximation ◽  
Stellar Nucleosynthesis ◽  
Exclusive Processes ◽  
Capture Cross Sections

In the first stage of this work, we perform detailed calculations for the cross sections of the electron capture on nuclei under laboratory conditions. Towards this aim we exploit the advantages of a refined version of the proton-neutron quasiparticle random-phase approximation (pn-QRPA) and carry out state-by-state evaluations of the rates of exclusive processes that lead to any of the accessible transitions within the chosen model space. In the second stage of our present study, we translate the abovementionede--capture cross sections to the stellar environment ones by inserting the temperature dependence through a Maxwell-Boltzmann distribution describing the stellar electron gas. As a concrete nuclear target we use the66Zn isotope, which belongs to the iron group nuclei and plays prominent role in stellar nucleosynthesis at core collapse supernovae environment.

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