For the sequential process of coincident photoelectron and Auger electron e
mission it is demonstrated that electron exchange and post-collision intera
ction can lead, due to constructive interference effects, to a remarkably i
ntense third line. The selected example is 4d(5/2) photoionization in xenon
with subsequent N-5-O2,3O2,3 S-1(0) Auger decay. Here the photoelectron li
ne is placed 25 units of the width of the intermediate hole-state below the
Auger electron line, and the relative angle between, the emitted electrons
is set to 12 degrees. The quantitative agreement between experimental data
and theoretical results, obtained in the one-step model, confirms the theo
retical treatment for a critical case of correlated two-electron emission.