Doppler spectroscopy of hydrogen atoms from the photodissociation of saturated hydrocarbons and methyl halides at 157 nm

Hydrocarbons (CnH2n+2, n=3, 4, and 6) and methyl halides (CH3X, X=Cl, Br, I) are photodissociated at 157 nm. The hydrogen atom photofragments are detected by a resonance-enhanced multiphoton ionization technique. The Doppler profiles of the hydrogen atoms from hydrocarbons are well represented by a Gaussian profile, while those from methyl halides by a mixture of a Gaussian and a non-Gaussian profiles. These Doppler profiles are interpreted assuming that (a) hot ethyl photofragments from hydrocarbons result in the formation of hydrogen atoms and (b) methyl halides undergo both direct and indirect photolytic scissions of the C—H bonds at 157 nm.