Spin-isospin excitations in the direction of β+ decay for Zn80 and Ru126 at finite temperature

Abstract

We investigate the Gamow-Teller (GT) and spin-dipole (SD) transitions in the direction of ${\ensuremath{\beta}}^{+}$ decay for neutron-rich $N=50$ nucleus $^{80}\mathrm{Zn}$ and $N=82$ nucleus $^{126}\mathrm{Ru}$, which are important for deleptonization phase in core-collapse supernova, at $T=0,\phantom{\rule{0.16em}{0ex}}1,\phantom{\rule{0.16em}{0ex}}2$ MeV with finite-temperature proton-neutron relativistic (quasiparticle) random-phase approximation. At zero temperature, the ${\mathrm{GT}}^{+}$ transitions for $^{80}\mathrm{Zn}$ and $^{126}\mathrm{Ru}$ are almost completely Pauli blocked because one more extra shell is occupied for neutrons than that for protons. With increasing temperature to even 2 MeV, the thermal excitation still cannot open up ${\mathrm{GT}}^{+}$ transitions with strong strength. The ${\mathrm{SD}}^{+}$ transitions in $^{80}\mathrm{Zn}$ are mildly affected by temperature, which means the experimental data measured at the laboratory can provide useful information for transitions in an astrophysical environment. However, for ${\mathrm{SD}}^{+}$ transitions in $^{126}\mathrm{Ru}$, the transition energies have a decrease of about 2 MeV from zero temperature to $T=1$ MeV due to the collapse of pairing gap of transition orbitals. The total strength in ${T}^{+}$ channel decreases with increasing temperature for both GT and SD transitions, due to the suppression of their transition strength induced by temperature effects.