Slow photoelectron imaging

Experiments are reported on the detection of slow photoelectrons resulting from the photoionization of Xe atoms in a de electric field by electron ima ging. In the far-held photoelectron velocity distributions we can distingui sh between direct and indirect ionization processes (involving long range C oulomb interactions with the Xe+ ion). Also, a new modulation of the veloci ty distribution is observed which cannot be explained by previously discuss ed mechanisms. Classical and quantum mechanical calculations are presented to support the interpretations.