The photoionization dynamics of the three structural isomers of dichloroethene

Using tunable vacuum-UV radiation from a synchrotron, the threshold photoelectron spectrum, threshold photoelectron photoion coincidence spectrum and ion breakdown diagram of the 1,1, cis-1,2 and trans-1,2 isomers of C\(_2\)H\(_2\)Cl\(_2\) have been recorded in the range 9-23 eV. The energies of the peaks in the threshold photoelectron spectrum are in good agreement with outer-valence Greens function caculations. The major difference between the isomers, both predicted and observed experimentally is that the F and G states of C\(_2\)H\(_2\)Cl\(_2^+\) are approximately degenerate for 1,1 and trans-1,2, but well separated for the cis-1,2 isomer. The ground and low-lying valence states of C\(_2\)H\(_2\)Cl\(_2^+\) are bound, with higher-lying states dissociating to C\(_2\)H\(_2\)Cl\(^+\) or C\(_2\)H\(_2^+\). The translational kinetic energy release into C\(_2\)H\(_2\)Cl\(^+\) + Cl is determined as a function of energy. Isolated-state behaviour for the low-lying electronic states of C\(_2\)H\(_2\)Cl\(_2^+\) becomes more statistical as the energy increases.