On the two-body dissociation of dications of water isotopologues

Abstract

Multiple ionization of water isotopologues is studied using near-IR fs laser beams and asymmetric ω/2ω phase-locked fields, in order to elucidate the involved dissociation mechanics and isotopic effects. The double ionization mechanism of water is identified by the laser polarization dependence of the released, via two body fragmentation, ions. The angular distribution of the H+/D+ fragments, reveal the participation of different molecular orbitals in the ionization process, indicating excitation of both the ground and first few excited states of the dications. The rate of the dissociative processes of the dication is found to be different for the two isotopologues, highlighting an isotopic effect. Inspection of the H2+/D2+ fragments formed prior to dissociation, reveals that they may have been generated from parent cations and parent dications. In the case of dication fragmentation, we find evidence of autoionization. Finally, the formation of the H2+/D2+ ions, is completed within the duration of the pulse.