Decay mechanisms of CH3 in 3-methylpentane and 3MP-d14 glasses at 77 °K as indicated by methane yields

Abstract

The isotopic methane yields from γ irradiation of 3‐methylpentane, 3MP–1%CH₃I, 3MP‐d₁₄–1%CH₃I, and 3MP‐d₁₄–1%CD₃I glasses confirm recent evidence from decay kinetics that thermal CH₃ radicals can abstract H from C–H bonds in hydrocarbon glasses at 77°K (plausibly by tunneling) and show that similar abstraction does not occur from C–D bonds. Also, in 3MP‐d₁₄ the CH₃ (formed by the CH₃I+e⁻ → CH₃+I⁻ process) does not decay by radical combination processes (CH₃+CH₃ or CH₃+C₆D₁₃), implying that decay is by geminate recombination with the I⁻ partner. In the γ irradiation of 3MP‐d₁₄–1%CH₃I irradiated at 77°K, G (CH₃D) from hot abstraction by CH₃ is 0.7; thermal CH₃ and CD₃ radicals are able to abstract H from low concentrations of C–H bond isotopic impurities; and the yields of scavengeable electrons and of radicals are substantially different than in 3MP‐h₁₄.