TEMPERATURE-ENHANCED ELECTRON DETACHMENT FROM C6F6- 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, tau(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 C6F6- initially increases slightly with increasing T below 500 K and subsequently decreases with further increases in T.