An angular correlation function for double photoionization in atoms

We consider the successive emission of two electrons following the absorpti on of a photon by an atom. An expression for the angular correlation betwee n the emitted electrons is derived in terms of the angle between their dire ctions of propagation, following the generalized approach of Biedenharn and Rose (Rev. Mod. Phys. 25 (1953) 729). Our theory treats double photoioniza tion as a two-step process and does not refer to perturbation theory. The d ynamics of the process are embodied in the reduced matrix elements. It is c lear that angular correlation is closely related to the coupling of the ang ular momenta. A sample computation is made for double photoionization in ar gon leading to the 3p(-2) D-1(e) final ionic state. (C) 2001 Elsevier Scien ce B.V. All rights reserved.