Differential cross sections (DCSs) for excitation of the C-H stretch vibrations for CH 3 F, CH 3 Cl, CH 3 Br and CH 3 I were measured by electron impact. Resonance enhancement was observed for the C-H stretch at 6.6, 5.9, 5.5 and 4.7 eV respectively. For CH 3 F this is attributed to a 2 A 1 shape resonance formed through temporary occupation of the LUMO and for the heavier halogens to a 2 E shape resonance formed through temporary occupation of the LUMO+1. DCSs for excitation of the C-X stretch were also measured for CH 3 F and CH 3 Cl. The shift in the resonance energy is discussed in context to the substitution effect of the halogens.
|Number of pages||6|
|Journal||Journal of Physics B-Atomic Molecular and Optical Physics|
|Publication status||Published - 2010|