Thermal electron attachment to van der Waals molecules (O2 ⋅ C2H6)

Using microwave conductivity technique with pulse radiolysis, thermal electron attachment in O2–C2H6 mixtures is studied at various temperatures (−120–100 °C) and C2H6 densities (7×1017–3×1019 molecules cm−3). van der Waals (vdW) molecules (O2 ⋅ M) (M; a third-body molecule C2H6) are clearly shown to contribute to electron attachment even at low densities of M. A large rate constant value for the initial electron attachment to vdW molecules, k5=(1.9+1.0−0.6 ×10−4(1/T)3/2 exp[−(3.5±0.6)×102/T]cm3 s−1, where T is the absolute temperature, is elucidated by a smaller resonance energy (30±5) meV as compared with that of an isolated oxygen molecule and by a larger resonance width of (O2 ⋅C2H6), (4.5+2.5−1.5)×10−4 eV. A dissociative electron attachment to vdW molecules is negligible in the vdW molecule mechanism.