Mechanism of thermal electron attachment in O2–C2H4, O2–CO2, and O2–neopentane mixtures

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Abstract
Thermal electron attachment of O2 in O2–C2H4, O2–CO2, and O2–neopentane mixtures has been investigated at room temperature, using a microwaveconductivity technique combined with pulse radiolysis. The measurements have been extended to a higher pressure region (∼850 Torr) than previous observations in order to compare them with the results of an electron swarm method at very high pressures. From low pressure data, the values of (2.0±0.3) ×10−30, (3.2±0.3) ×10−30, and (7±1) ×10−30 cm6/molecule2 sec are determined for the overall three body attachment rate constants of O2 with the stabilizing partners C2H4, CO2, and neopentane, respectively. In each case, the effective rate constant continued to increase with increased density and exceeded those predicted by the Bloch–Bradbury mechanism by sizeable amounts. The excess attachment is suggested to involve pre‐existing van der Waals complexes such as (O2⋅C2H4). Some quantitative conclusions which follow from this mechanism are given.