Angular Correlation in Double Photoionization of Atoms and the Role of the Observer

Abstract

The problem of angular correlation in the double photoionization (DPI) of rare gas atoms is considered in some depth. We refer particularly to the efficiency operator for the detection of an electron by a detector having the shape of a right circular cylinder. The different factors in the efficiency operator are discussed in detail keeping in mind the fundamental epistemological question of the role of the observer (or his equipment) in such experiments.