ION-IMPACT-INDUCED FRAGMENTATION OF WATER-MOLECULES

The multiple ionization and fragmentation of H2O by fast H+, He+, O6+ and O7+ ions was studied utilizing a position- and time-sensitive multi-particle detector which allows the coincident measurement of the momenta of correlated fragments. Thereby, the fragmentation energy and angular correlations for each individual event can be derived. Of special interest are the processes H2O --> H+ + H+ + O-q+, where a simple Coulomb-explosion model is insufficient to explain the measured energy and angular spectra. Better agreement was achieved with ab initio MCSCF calculations which take into account several molecular states of the fragmenting highly charged (HO(q+2)-O-2+) ion.