The photodissociation of methane atLyman cz (1216 3,) has been the focus of much scrutiny over the past few years. Methane photolysis leads to the formation of H2 molecules as well as H, CH, 1CH2, 3CH2, and CH3 radicals, which promote he propagation f hydrocarbon chemistry. However, recent studies [Mordaunt et al., 1993; Romani, 1996; Smith and Raulin, 1999] have not fully resolved the issue of...