Chapter 10 - Radiative electron capture (REC)

Abstract

The chapter discusses the approach that treats radiative electron capture (REC) within the impulse approximation. For free electrons, capture cannot take place at all without the emission of photons, owing to energy and momentum conservation. This means qualitatively that electrons loosely bound in low-Z target atoms or outer shells are more likely to be captured with a photon emission than without. A loosely bound target electron may be considered as approximately free in a high-energy collision. The nonrelativistic Born approximation for K-shell photoionization providing a simple access to qualitative features of REC is also discussed in the chapter. In this limit, REC is identical to radiative recombination, in which an electron initially moving with the velocity in the projectile frame is captured into a bound state of the projectile with the simultaneous emission of a photon of energy and a wave number. The Stobbe formula for K-shell photoionization and REC are also derived in the chapter.