Angular and Energy Distributions of K+ and I– Ions in Dissociation of KI Molecules at a Diamond Surface

Scattering of K+ and I– ions in surface-induced dissociation of KI molecules at a diamond (110) target has been studied using the molecular beam techniques. The angular and energy distributions of the positive and negative ions were measured by a time-of-flight detector with a retarding field energy analyzer. The incident KI beam energy was equal to 12 eV while the target surface temperature was 250°C. The angular distributions of the K+ ions we observed exhibited maxima at scattering angles smaller than the specular reflection ones, in contrast to the I– ion distributions where the maxima were shifted to larger angles. The intensities of scattering of both the ions at the maxima of the distributions increased as the incident angles of the beam grew. The energy distributions of the positive and negative ions have turned out to be identical which may indicate the mechanism of rapid non-statistical dissociation of the molecules upon an impact on the target surface.