Shape Resonance Influence on the Photoelectron Angular Distributions from O2C 3 Pi(g), v=0-3

摘要

Vibrationally resolved, photoelectron angular distributions are reported for the (2+1) REMPI of the C 3 Pi sub g (3s) (sigma sub g), nu1 = 0-3 Rydberg levels of O2. Ionization transitions leading to different vibrational final states (nu+) of O2(+) exhibit markedly different angular distributions, suggesting different ionization mechanisms. The experimental data are qualitatively reproduced by very recent ab initio calculations which attribute the non-Franck-Condon behavior to the presence of a k(sigma sub u) shape resonance imbedded in the ionization continuum. Much of the remaining anomalous behavior is attributed to a Fano-type resonance in the Pi sub u channel. Keywords: Resonantly enhanced multiphoton ionization; Multiphoton ionization; Photoelectron spectroscopy; Shape resonance; Molecular oxygen; Rydberg levels; Reprints. (JHD)