Postcollision Interaction in the Coincident Emission of Photoelectrons and Auger Electrons at Small Relative Angles

Postcollision interaction effects have been investigated for sequential two-electron emission in xenon for particular kinematical conditions, small relative angles between the emitted electrons, and selected energies ${\ensuremath{\epsilon}}_{a}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}{\ensuremath{\epsilon}}_{b}$ which are halfway in between the nominal values of the ``photo''-electron and the ``Auger'' electron. The experimental results are in good agreement with the theoretical prediction. Our successful technique to measure two coincident electrons of nearly the same energy and the same directions opens a plethora of possibilities to probe for different cases the Coulomb interaction of three charged particles and the impact of the intermediate resonance state.