Resonant photofragmentation of core-excited water molecules has been studied with high-resolution partialion-yield spectroscopy. Both the single and coincidence channels were monitored simultaneously. A steep increase in the coincidence yield curves above the ionization threshold, where the normal Auger decay produces doubly charged or multiply charged species that yield two or more charged fragments, has been observed. By comparing the single and coincidence channels the relative weight of H neutral fragments has been qualitatively assessed, and found to be higher for the O 1s→4a 1 primary excitation. The presented ion-yield data provide strong evidence for a branching between atomic Auger decay and molecular fragmentation in the O ϩ channel. The most unexpected result is the formation of H 2 ϩ species being detected and attributed to a highly excited bending mode. ͓S1050-2947͑99͒00601-0͔

A complete description of the 4sigma photoionization dynamics of NO has been derived from angle resolved photoelectron-photoion-coincidence experiments. The combination of measurements performed with linearly and circularly polarized light has made it possible to obtain a unique set of complex dipole matrix elements. A comparison with multichannel-Schwinger-configuration-interaction calculations shows good agreement in the general shapes of the angular distributions due to the correct description of the main components and phase differences. Still, many transition moments agree only qualitatively.

Resonant photofragmentation of core-excited methanol has been studied with highresolution partial ion-yield spectroscopy near both the carbon and oxygen K-edge. Non-coincident and coincident fragmentation channels were monitored simultaneously. A steep increase in the coincidence yield curves above the ionization threshold, where the normal Auger decay produces doubly charged or multiply charged species which yield two or more charged fragments, has been observed. A relevant difference in resonant structure has been observed while comparing the fragmentation at the carbon K-edge and the oxygen K-edge. Evidence for inter-atomic Auger decay is presented for one particular single channel around the oxygen K-edge.

Molecular ionization and ionic fragmentation of core excited CO valence and Rydberg states are studied by partial-ion-yield spectroscopy at vibrational resolution. The vibrational intensities of the Rydberg excitations differ significantly depending on the ionization and/or fragmentation channel. The observed intensity variations are explained by nondissociative excited final ionic states of the subsequent molecular Auger decay. The vibrational levels of these final states become selectively depopulated due to interaction with dissociative decay channels leading to ionic fragmentation.

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