EFFECT OF TEMPERATURE ON ELECTRON-ATTACHMENT TO AND NEGATIVE-ION STATES OF CCL2F2

The effect of temperature on electron attachment to dichlorodifluorome thane (CCl2F2) has been investigated for temperatures up to 500 K and for mean-electron energies from thermal to 1.0 eV using an electron sw arm method. The measurements were made in mixtures of CCl2F2 with nitr ogen. The electron attachment rate constant increases with temperature over the entire temperature and mean-electron energy range investigat ed. 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 tempera ture 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 scatterin g, electron transmission, indirect electron scattering, and related ca lculations, the lowest negative ion states of CCl2F2 have been identif ied with average positions as follows: a(1)(C-Cl sigma) at +0.4 eV an d -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 resonanc e is also indicated at -8.9 eV. (C) 1998 American Institute of Physics . [S0021-9606(98)02043-1].