Shape resonance influence on the photoelectron angular distributions from O2 C 3Pi/sub g/, v = 0--3

Vibrationally resolved, photoelectron angular distributions are reported for the (2+1) REMPI of the C 3Pi/sub g/(3sσ/sub g/), v' = 0--3 Rydberg levels of O2. Ionization transitions leading to different vibrational final states (v+) of O+2 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 kσ/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