Effect of temperature on the attachment of slow (≤1 eV) electrons to CH₃Br

The electron attachment rate constant k_a(〈∈〉, T) for CH₃Br has been measured in a buffer gas of N₂ using a high pressure electron swarm apparatus, within the mean electron energy range from thermal ( ≃0.046 eV ) to 0.87 eV and over the temperature range, T, 300-700 K. At room temperature, CH₃Br attaches low energy electrons weakly but as T is raised from 300 to 700 K the total electron attachment cross section increases by more than 2 orders of magnitude. At T=300 K the electron attachment cross section exhibits a peak at 0.38 eV which shifts progressively to lower electron energies as T is increased. The thermal value of k_a is 1.08 X 10^-11 cm³ s^-1 at 300 K and 3.28 X 10^-9 cm³ s^-1 at 700 K.