A photoelectron spectroscopic study of ionization selectivity in resonantly enhanced multiphoton ionization of Xe and Kr

Photoelectron energy and angular distribution measurements were carried out for resonant multiphoton ionization (MPI) of Xe and Kr through some Rydberg excited states under collision-free conditions. From the (3+1) resonant MPI of Xe through the 5d[2 1/2]0 J=3 Rydberg state, it has been clearly demonstrated that removal of a Rydberg electron gives rise to only the 2P3/2 ionic state. Such selectivity has also been observed for the 5d[3 1/2]0 J=3 Rydberg state of Xe and the 5s[1 1/2]0 J=1 Rydberg state of Kr. For the 6s[1 1/2]0 J=1 Rydberg state of Xe, however, both the 2P1/2 and 2P3/2 states are produced. This breakdown of the one-electron ionization picture may be due to the near resonance in the fourth-photon level. Photoelectron angular distributions obtained here for the resonant MPI of Xe and Kr show obvious deviations from the cosine square distribution, reflecting the spatial alignment of the total electronic angular momentum in the resonant Rydberg states.