Decay mechanisms of CH3 in 3-methylpentane and 3MP-<i>d</i>14 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.