Particle-Induced Electromagnetic De-Excitation of Nuclei in Stellar Matter

Abstract

The rate for electromagnetic de-excitation of excited nuclei by inelastic scattering with electrons and ions in stellar matter is calculated as a function of temperature, density, transition energy, and multipole type. The results of this paper indicate that for temperatures in the range ${10}^{9}\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}<T<{10}^{10}\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}$ and densities in the range ${10}^{9} \mathrm{g}/{\mathrm{cm}}^{3}<\ensuremath{\rho}<{10}^{12} \mathrm{g}/{\mathrm{cm}}^{3}$, particle-induced electromagnetic de-excitations compete favorably with spontaneous radiative transitions. As an example, a ${\mathrm{C}}^{12}$ nucleus, put in the 7.65-MeV ${0}^{+}$ excited state and imbedded in an electron-helium plasma with a density of ${10}^{11}$ g/${\mathrm{cm}}^{3}$, will be de-excited by electromagnetic interaction with the plasma 40 times faster at $T={10}^{9}\ifmmode^\circ\else\textdegree\fi{}$K and 500 times faster at $T={10}^{10}\ifmmode^\circ\else\textdegree\fi{}$K than its natural radiative rate. At the lower temperature the de-excitation is dominated by the electrons, and at the higher temperature by the helium ions. The conditions for the applicability of the present work to modern astrophysical problems are discussed.