MULTI-PHOTON IONIZATION SPECTRA OF POLYCYCLIC ALKANES

Three-photon ionization spectra, resonant at the second photon, have been obtained for cyclohexane and the polycyclic systems norbornane, trans -decalin, adamantane, hexamethylene tetramine, and bicyclo[2.2.2]octane in the 3580-5000 Å one-photon region. In each of the alkanes, a well-structured excitation to the 3s Rydberg orbital was observed, with term values following the convergent pattern established for other highly alkylated chromophores. The prominent excitation of t2 and e vibrations in the lowest Rydberg band of adamantane is suggestive of Jahn-Teller distortion in the upper state. Nontotally symmetric vibrations were observed with less certainty in the two-photon excitations to 3s in cyclohexane and bicyclo[2.2.2]octane. © 1979 American Institute of Physics.