Strong correlation effects in atomic photoelectron angular distributions far above thresholds - art. no. 042718

We scrutinize individual interchannel coupling effects on atomic dipole and nondipole (E1-E2) photoelectron angular distribution parameters of valence electrons far above thresholds, choosing 2p photoionization of N and Ne in the photon energy range from 1 to 10 keV as case studies. It is found that individual correlation effects are strong far above thresholds. However, a cancellation effect is also discovered that largely obviates the net corre lation effect on photoelectron angular distributions. It is shown that the cancellation can be removed, i.e., strong correlation effects can be observ ed, by considering core-ionized (core-excited) initial states: this is expe cted to be quite general. The importance of this work is that it shows that the tacit belief in the insignificance of correlation in nondipole paramet ers far above thresholds is quite misleading. In addition, it suggests stud ies of core-ionized or core-excited atoms as a means of exploring these lar ge correlation effects in nondipole photoelectron angular distributions far above thresholds.