Temperature-enhanced electron detachment from C₆F ₆^- negative ions

A method is described whereby photoelectrons generated by a short laser pulse at the cathode of a parallel-plate electrode arrangement are depleted by attachment to C₆F₆ molecules mixed with N₂ in the interelectrode space as they drift to the anode under an externally applied electric field. The contribution of the initially produced (prompt) and the delayed (autodetached from C₆F₆^-) electrons to the induced signal in the detector circuit is recorded as a function of time following the laser pulse and also as a function of gas number density, applied electric field, and gas temperature, T. Increases in T from ambient to 575 K enhance dramatically the autodetachment frequency, τ_d ^-1, for C₆F₆^-. This heat-activated autodetachment correlates with the increase in the internal energy of the anion and has an activation energy of 0.477 eV. Electron attachment producing C ₆F₆^- initially increases slightly with increasing T below 500 K and subsequently decreases with further increases in T.