Transitions in the electronic absorption spectra of c i s- and t r a n s-difluoroethylene

The absorption spectra of cis- and trans-difluoroethylene and their perdeuterated isomers were measured between 1200 and 1650 Å. The spectrum of each molecule is analyzed into several Rydberg series to the lowest ionization potential, and the 3s-Rydberg transition to the second ionization potential of the trans-molecule. Interactions are observed between the 3d and 4s Rydberg transitions in cis-difluoroethylene and between the 3s transition to the second ionization potential and the entire s-Rydberg series in trans-difluoroethylene. From these interactions the d-Rydberg series in each molecule is deduced to be a dδ series.