DISSOCIATION DYNAMICS OF DOUBLY-CHARGED AND TRIPLY-CHARGED MOLECULES STUDIED BY THE TRIPLE PHOTOELECTRON PHOTOION PHOTOION COINCIDENCE METHOD

The photoelectron-photoion-photoion coincidence (PEPIPICO) technique has been used together with a source of synchrotron radiation to elucidate the dissociation dynamics of doubly- and triply-charged molecules, i.e., carbonyl sulfide (OCS), sulfur dioxide (SO2), and methyl fluoride (CH3F). Using the flight time distributions of the lighter and heavier ions produced in pairs, we determined whether the dissociation occur simultaneously or in sequential stages. It was found that for the three-body dissociation of the type A BC2+ --> A + + B+ + C, the dissociation mechanism is not dependent on the excitation energies over the range of 46-80 eV. This phenomenon suggests the presence of two site-specific positive holes each of which is related to a particular dissociation pathway. It is additionally concluded that atomization of the precursors is a dominant process in OCS and SO2 at higher excitation energies.