Dissociation of MeV HeH+ ions at glancing angle incidence on clean (001) surface of SnTe

Angular and energy distributions of scattered fragments have been measured at glancing angle incidence of MeV HeH+ ions on a clean (001) surface of SnTe crystal. The distributions show that the internuclear vectors between fragments tend to align with the beam direction and the kinetic energy of the fragments acquired by the dissociation is smaller than that released at He2+-H+ explosion. The alignment of the internuclear vectors is explained in terms of a surface wake potential due to dynamic response of surface electrons to the charges of fragments. The observed kinetic energy indicates that most of the HeH+ ions are excited to some excited states without loss of electrons and dissociate into pairs of He and H ions on the incoming trajectories and the loss of electrons of the fragments does not occur until the internuclear distance of the pairs becomes a few times of the ground state one. (author)