The Be-7 Electron Capture Rate in the Sun

Abstract

For solar conditions, we numerically integrate the density matrix equation for a thermal electron in the field of a Be-7 ion and other plasma ions and smeared-out electrons. Our results are in agreement with previous calculations that are based on a different physical picture, a picture which postulates the existence of distinct continuum and bound state orbits for electrons. The density matrix calculation of the electron capture rate is independent of the nature of electron states in the solar plasma. To within a 1% accuracy, the effects of screening can be described at high temperatures by a Salpeter-like factor which can be derived from the density matrix equation. The total theoretical uncertainty in the electron capture rate is about 2%.