Dependence of the distributions of kinetic energies of products on photoionization energy in the photodissociation of ethene at 157Â nm

The dependence of distributions of kinetic energies of H2 and C2H2 products on energy of photoionization is investigated upon photodissociation of ethene at 157 nm. The average kinetic energy of each product decreases with decreasing energy of photoionization, but more markedly for H2 than for C2H2. The dissociation of CH2CD2 into C2H2 + D2 and C2HD + HD differentiates 1,1- from 1,2-elimination of molecular hydrogen. With increasing photon energy, the ratio of HD to D2 decreases and of C2HD to C2H2 increases in both kinetic energy and intensity of product signals. The internal energies of products are roughly estimated.