Dissociative attachment to excited SF6:: selective IR excitation versus thermal activation

Vibrational excitation of the v(3) mode of SF6 by a CO2 laser, followed by electron attachment, leads to a very sharp enhancement in the dissociative electron attachment (DEA) process SF5- + F at 0 eV electron energy, but does not affect the intensity of the metastable SF6-. This is in striking contrast to thermal heating where SF5- is enhanced within a broad electron energy range and the SF6 intensity strongly decreases. In the framework of localized potential energy surfaces the effect of the v(3) mode for the DEA reaction at 0 eV is explained by the level of the curve crossing between the neutral and anionic system matching the energy of the v(3) vibration. (C) 2004 Elsevier B.V. All rights reserved.