Towards a Complete Theory of K Electron Ejection During β Decay: An Examination of the Direct Collision Mechanism

Abstract

It has been long known that nuclear 3 decay is sometimes accompanied by the ionization of a member of the electron cortege of the daughter atom. This process, known as internal ionization during 3 decay, was first studied by Feinberg¹ and Migdal² almost forty years ago. In their pioneering work, the two principal mechanisms by which this process can occur, known as shake-off (SO) and direct collision (DC), were first identified. Also, it was concluded, on the basis of various estimates, that the dominant contribution to the internal ionization probability is, under most circumstances, from SO, with DC contributing a small correction at most. Consequently, the focus of subsequent theoretical work has been the SO process, with detailed calculations usually restricted to the determination of P_K(SO), the total K-shell internal ionization probability per β decay due to SO alone. The DC contribution has either been totally ignored or compensated for through the use of Born approximation-like results or simple ad hoc prescriptions based on Feinberg’s estimates.