Effect of temperature on electron attachment to and negative ion states of CCl2F2

The effect of temperature on electron attachment to dichlorodifluoromethane (CCl2F2) has been investigated for temperatures up to 500 K and for mean-electron energies from thermal to 1.0 eV using an electron swarm method. The measurements were made in mixtures of CCl2F2 with nitrogen. The electron attachment rate constant increases with temperature over the entire temperature and mean-electron energy range investigated. The variation of the thermal value of the electron attachment rate constant with temperature compares well with earlier measurements of this quantity and shows an increase by a factor of 10 when the temperature is raised from 300 to 500 K. From a comparison of published data on the electron affinity, electron attachment using the swarm method, electron attachment using the electron beam method, electron scattering, electron transmission, indirect electron scattering, and related calculations, the lowest negative ion states of CCl2F2 have been identified with average positions as follows: a(1)(C-Cl sigma*) at +0.4 eV and -0.9 eV, b(2)(C-Cl sigma*) at -2.5 eV, a(1)(C-F sigma*) at -3.5 eV, and b(1)(C-F sigma*) at -6.2 eV; an electron-excited Feshbach resonance is also indicated at -8.9 eV. (C) 1998 American Institute of Physics. [S0021-9606(98)02043-1].