Electron-Nucleus Neutrino Bremsstrahlung

The neutrino energy rate arising from bremsstrahlung reactions of the type $\mathrm{nucleus}+e^{-}\to \mathrm{nucleus}+e^{-}+\nu +\tilde{\nu }$ is computed in a relativistic context at various densities and temperatures of matter. The density regions of degeneracy, partial degeneracy, and nondegeneracy of the electron sea are considered. It is found that the bremsstrahlung reaction is the dominant neutrino-producing mechanism in the extreme degeneracy region, as previously found by Festa and Ruderman. It dominates also for partial degeneracy if the atomic number $Z$ of the nuclei is not too low and for temperatures lower than 2-3×${10}^9$ °K, while it is negligible in the nondegenerate regions. Our results agree very well with those of Festa and Ruderman in the limit of very high densities. The electron-nucleus bremsstrahlung rate is also compared for extreme degeneracy with the electron-electron bremsstrahlung rate, which was studied by two of us in the nondegenerate case. It is shown that $e-e$ collisions give a negligible contribution in comparison with $e$-nucleus reactions.