A full dimensional direct ab initio dynamics study of the electron captureby SF6

The dynamics of electron capture by sulfur hexafluoride (SF6) have been inv estigated by means of full dimensional direct ab initio dynamics calculatio ns at the HF/6-311G(d)+sp (a diffuse sp-function is further added to sulfur atom) level. A rigid SF6 structure and narrow Franck-Condon region for ele ctron capture was assumed in choosing initial conditions for the trajectori es. The direct ab initio dynamics calculations for the electron capture pro cesses by SF6 indicated that the SF6- ion formed by the vertical electron a ttachment to SF6 decomposes into SF5- and F via short-lived complex formati on (SF6-). The lifetime of SF6- was distributed from 0.1-0.2 ps, which is q uite short as lifetime of the intermediate complex. The dynamics calculatio ns showed that 12% of the total available energy is partitioned into the re lative translational mode between SF5- and F. The effect of solid phase on the dynamics has been examined by introducing a model bath-relaxation time for energy dispersion. There was a possibility that the SF6- anion exists i n solid phase. The mechanism of the electron capture by SF6 in gas phase an d in solid phase was discussed on the basis of the results. (C) 2001 Elsevi er Science B.V. AII rights reserved.