Electron capture and drift in polyatomic gases

Electron drift velocities and lateral diffusion coefficients for a number of polyatomic gases were employed to determine mobilities, mean fractional energy losses per collision, stopping rates, derivatives of stopping rates with respect to the mean electron energy, and thermalization times as a function of mean electron energy. These calculations are presented and discussed. The data indicate that direct excitation of rotational states in H2O and the deformation, bending, and torsional vibrational modes in CH4, C2H2, C2H4, C2H6, C-C3H6, and C3H8 is an important energy loss process for slow electrons. Drift velocities were measured for some polyatomic gases, and the resulting mobilities were compared to those measured in the liquid phase. Attachment studies in SF6 have extended the range of energies over which data are available. Absolute rates and cross sections are reported. Measurements of electron attachment to C6F6 have revealed two separate capture processes, which have been attributed to capture into the degenerate π4 and π5 orbitals and capture into the π6 orbital. Attachment rates and cross sections are again given. Discussion of the autoionization lifetime of the C6F6-* ion leads to speculation that the energy of the negative ion is not shared by all the possible modes of vibration