TEMPERATURE-ENHANCED ELECTRON DETACHMENT FROM C6F6- NEGATIVE-IONS

A method is described whereby photoelectrons generated by a short lase r pulse at the cathode of a parallel-plate electrode arrangement are d epleted by attachment to C6F6 molecules mixed with N2 in the interelec trode space as they drift to the anode under an externally applied ele ctric field. The contribution of the initially produced (prompt) and t he delayed (autodetached from C6F6-) electrons to the induced signal i n the detector circuit is recorded as a function of time following the laser pulse and also as a function of gas number density, applied ele ctric field, and gas temperature, T. Increases in T from ambient to 57 5 K enhance dramatically the autodetachment frequency, tau(d)-1, for C 6F6-. 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 slight ly with increasing T below 500 K and subsequently decreases with furth er increases in T.