Sukhendusekhar Sarkar

Beta decay rates of fp shell nuclei in advanced evolutionary stages of presupernova stars

Abstract Presupernova evolutionary calculations require reliable rates of beta decay and electron captures on fp shell nuclei with A > 60, as their inclusion could have appreciable effects on stellar structure and the subsequent evolution towards supernova explosion. Here we calculate the beta decay rates of a few of these nuclei by using Gamov-Teller sum rule strength that employ nucleon occupancies obtained by spectral averaging methods. The method is well suited for the finite temperatures typical of presupernova cores and includes relevant excited states of the mother nucleus.

Half-lives and presupernova weak interaction rates for nuclei away from the stability line

A detailed model for the calculation of -decay rates of the fp shell nuclei for situations prevailing in presupernova and collapse phases of evolution of the core of massive stars leading to supernova explosion has been extended for electron-capture rates. It can also be used to determine the half-lives of neutron-rich nuclei in the fp/fpg shell. The model uses an averaged Gamow-Teller (GT) strength function, but it can also use the experimental log ft values and GT strength function from (n, p) reaction studies wherever available. The calculated rate includes contributions from each of the low-lying excited states of the mother including some specific resonant states (`back resonance) having large GT matrix elements.A detailed model for the calculation of beta decay rates of the

Gamow-Teller strengths in fp shell

fp

Gamow-Teller strength sums for nuclei in the fp shell

shell nuclei for situations prevailing in pre-supernova and collapse phases of evolution of the core of massive stars leading to supernova explosion has been extended for electron-capture rates. It can also be used to determine the half-lives of neutron-rich nuclei in the

Spectral distribution theory—Some recent applications

fp/fpg

PAIRING AND SHELL EVOLUTION IN NEUTRON RICH NUCLEI

shell. The model uses an averaged Gamow-Teller (GT) strength function. But it can also use the experimental log ft values and GT strength function from

Excited States of 71Ge above the Neutron Emission Threshold and Solar Neutrino Capture Rates for Ga Detectors

(n,p)

Effect of inclusion of 1g orbits on the Gamow-Teller strengths for the capture rates of solar neutrinos in Ga detectors

reaction studies wherever available. The calculated rate includes contributions from each of the low-lying excited states of the mother including some specific resonant states (back resonance) having large GT matrix elements.

Beta Decay of Some FP Shell Nuclei for Presupernova Stars

Abstract We develop a simple parametrization based on the spectral distribution theory for the total Gamow-Teller (GT + ) strength in the f p shell, which reproduces the sum of the observed B (GT) of ( n , p ) experiments well and is useful for nuclear structure and astrophysical applications.

Shell model study of neutron rich nuclei near Sn-132

The Gamow-Teller strength sums are evaluated for nuclei in the fp shell using spectral distribution-methods and are compared with the available shell-model results. Decomposition of the beta - strength sum according to the final isospin (T=T-1, T, T+1) is also given.