Abstract
Negative ion formation in electron transfer experiments from fast neutral potassium (K) atom collisions with neutral tetrachloromethane (CCl4) molecules has been investigated in the laboratory frame range of 8-1000 eV. Comprehensive calculations on the electronic structure were performed for CCl4 in the presence of a potassium atom and used to help analyze the lowest unoccupied molecular orbitals participating in the collision process. Additionally, K+ energy loss produced in the forward direction has served to further our knowledge on the electronic state spectroscopy of CCl4. A vertical electron affinity of -0.79 +/- 0.20 eV has been obtained and assigned to a purely repulsive transition from CCl4 ground state to the( 2)T(2) state of the temporary negative ion yielding Cl- formation. Other features in the energy loss spectrum were observed for the first time and related to Cl-2(-), CCl2-, and CCl3- formation. Special attention is also given to the unresolved feature corresponding to a positive electron affinity of 0.24 +/- 0.2 eV, assigned to a vibrationally hot transition from CCl4 ground state into the triply degenerate T-2(2) excited state of the negative ion. The combined time-of-flight mass spectrometry together with K+ energy loss data represents the most comprehensive assignment of the tetrachloromethane anion yields and the role of CCl4 electronic states in collision induced dissociation to date.