Ion-pair dissociation of water molecule in vacuum ultraviolet photoabsorption as investigated by momentum imaging of fragment negative ions

A momentum imaging spectrometer for the detection of negative ions has been developed on investigation with a synchrotron light source for clarification of the dynamics of ion-pair photodissociation in the vacuum ultraviolet energy range. This method, combined with utilization of pulse character of synchrotron has been examined for the study of ion-pair photodissociation of H${}_2$O. It has been demonstrated that the present methodology provides comprehensive insights into the dynamics of ion-pair photodissociation, particularly in polyatomic molecules.