Ultra-violet absorption of trans-dichloro ethylene

Abstract

Improved spectra of trans-dichloro ethylene are reported. Interest centres mainly on a system of many sharp bands stemming from an origin at 1528 Å. A vibrational analysis is given and the transition shown to be Rydberg in type and associated with the removal of an electron from an orbital that is anti-symmetric with respect to reflection in the molecular plane and largely, but not completely, localized on the C atoms. The upper state and the ground state of the positive ion retain the C_2h symmetry of the ground state of the neutral molecule; but are deduced to have a longer CC bond, shorter CCl bonds and smaller ClCC angles. A previously reported first ionization potential value of 9.96 eV is not confirmed.