ABINITIO CALCULATIONS ON THE ONE-PHOTON AND 2-PHOTON ELECTRONIC-TRANSITIONS OF CYCLOPENTADIENE, SPIRONONATETRAENE, 1,4-CYCLO-HEXADIENE, DEWAR BENZENE, NORBORNADIENE, AND BARRELENE

Ab initio RPA calculations have been carried out on the low-lying singlet intravalence and Rydberg electronic states, accessed by one- and two-photon absorption, of representative cyclic systems. Two-photon spectroscopic properties that could be detected under various experimental arrangements have been reported. The relative displacements of the transitions brought about by spiroconjugation and bridge insertion are correctly accounted for. Information on the nature of the first valencelike excited states has also been achieved by CI-SD treatments.