Direct collisional scattering of the excited hydrogen atom: Doppler profile analysis in fast Ar+ ion collisions with acetylene and wthylene

The Doppler profiles and translational energy distributions of H∗ produced in Ar+−C2H2n(n = 2, 3) collisions have two major components. The slow component has a peak at about 10 eV and has been assigned as being produced through the dissociative excitation of the parent molecule. The fast component has a large translational energy with its peak up to 100 eV, and should be produced through direct collision between Ar+ and one of the H atoms in the molecule; the rest of the molecule is a spectator. The translational energy of the fast component is consistent with a hard-sphere collision model.