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

Vibrational excitation of the ν3 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 ν3 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 ν3 vibration.