Orientation and alignment effects in ion-induced fragmentation of water: a triple coincidence study

The technique of recoil ion momentum spectroscopy is employed to determine the complete momentum vectors for three fragment dissociation channels, [D2O]((q+2)) → (D(+) + D(+) + O(q+)) with q = 1, 2, or 3 formed in collisions of isolated water molecules with 450 keV Xe(9 +) ions. The kinetic energy released in each of these dissociation channels is measured and angular correlations between the fragment momenta are determined. From the angular correlations of the three fragment ions with the direction of the incoming beam, a strong anisotropy in the emission of recoil fragments is reported. It is inferred that the molecular plane prefers to lie orthogonal to the incoming beam direction with certain orientations being more preferred than others and a clear signature of non-coplanar dissociation is also observed.