A microscopic thermodynamically consistent approach is applied to compute electron capture (EC) rates and cross sections on nuclei in hot stellar environments. The cross-section calculations are based on the Donnelly-Walecka multipole expansion method for treatment of semileptonic processes in nuclei. To take into account thermal effects, we express the electron capture cross section in terms of temperature- and momentum-dependent spectral functions for respective multipole charge-changing operators. The spectral functions are computed by employing the self-consistent thermal quasiparticle random-phase approximation (TQRPA) with the Skyrme effective interaction. Three different Skyrme parametrizations (${\mathrm{SkM}}^{*}$, SGII, and SLy4) are used to investigate thermal effects on EC for ${}^{56}\mathrm{Fe}$ and ${}^{78}\mathrm{Ni}$. For ${}^{56}\mathrm{Fe}$, the impact of thermally unblocked Gamow-Teller ${\mathrm{GT}}_{+}$ transitions on EC is discussed and the results are compared with those from shell-model calculations. In particular, it is shown that for some temperature and density regimes the TQRPA rates exceed the shell-model rates due to violation of the Brink-Axel hypothesis within the TQRPA. For neutron-rich ${}^{78}\mathrm{Ni}$, the full momentum dependence of multipole transition operators is considered and it is found that not only thermally unblocked allowed $1^{+}$ transitions but also thermally unblocked first-forbidden $1^{-}$ and $2^{-}$ transitions favor EC.

• Received 20 March 2019
• Revised 7 June 2019

DOI:https://doi.org/10.1103/PhysRevC.100.025801