Molecular dissociation of D2+ scattered from a polycrystalline nickel surface

We compare time of flight spectra of atomic D+ and molecular D2+ ions specularly scattered from a polycrystalline nickel surface at 4° of incidence and with a velocity corresponding to 1 keV/u. Molecular dissociation is assumed to occur mostly upon resonant neutralisation into the antibonding triplet state of D2. The kinetic energy released in the dissociation (KER) is distributed over both atomic fragments. We consider the D2+ spectrum as the result of atomic projectiles hitting the surface at different energies and different incidence or azimuthal angles given by the cinematic of the fragmentation. The electronic density of states of Ni, the vibrational levels of D2+ and the image potential shift are taken into consideration to calculate the KER distribution. The resulting broadening function is then applied to the experimental D+ spectrum, which is finally compared to the spectrum of D2+. The good agreement found without any adjustable parameter is consistent with the assumption of a complete dissociation by resonant neutralisation on the incoming path.