Neutralisation and ionisation processes in the scattering of D+, D2+ and D3+ on a Mg surface

Results of a time of flight (TOF) study of charge fraction measurements of positive and negative ion production in the scattering of D+, D2+ and D3+ by a polycrystalline Mg surface in the low keV energy range are presented. The ion fractions are found to be small, the positive ion fractions being in the range 0.02-0.2% are an order of magnitude smaller than the negative ion ones which are in the range 0.4-6.0%. The negative ions must be D-. Our results indicate that the positive ions are dominantly atomic also. The charge fractions are found to scale with the energy per nucleon whatever the incident ions. This could be related to a dominantly total dissociation of the molecules with subsequent interaction of the scattered D atoms with the surface leading to positive and negative ion production. Resonant neutralisation into repulsive excited states may be one of the main dissociative processes. (author)