TWO-PHOTON EXCITATION SPECTRUM OF PERYLENE∗PERYLENE^{*}

Author Institution: Department of Chemistry, Michigan state UniversityThe two-photon excitation technique is being applied to fluorescent, centrosymmotric polycyclic hydrocarbons and heteronuclear aromatics. We report here TPE spectra of perylene $(C_{20}H_{12}$, peri-dinaphthalene), which has $D_{2h}$ symmetry. Both $A_{g}$ and $B_{g}$ excited electronic states - which are ``hidden"" in the normal absrption spectrum-are revealed in the 250-400 nm region when $\sim 10^{-4}$ M solutions of parylene in n-octane are irradiated by near infrared light from a tunable Nd: YAG-pumped dye laser. Assignments are based on the relative intersity of the two-photon anduced fluerescence under linear and circular polarization of the laser soures. The experimentally-determined excited state energies will be compared with published theoretical $calculations.^{1}$ $^{*}$Research supported in part by the U. S. National Science Foundation. $^{1}$Y. Tanizaki, T. Yoshinaga and H. Hiratsuka, Spectroship Acta 34A, 205 (1978)

RAMAN SPECTRUM OF PYRIDINE RESONANT TO THE s2(Π−Π∗)s_{2}(\Pi-\Pi^{*}) STATE∗STATE^{*}

Author Institution: College of Engineering, Nihon University, Koriyama; Department of Chemistry, Michigan State UniversityThe Raman spectrum to of pyridine $(C_{5}H_{5}N),$ resonant to the$S_{2} (\pi-\pi^{*})$ excited electronic state, has been studied in the vapor phase under 266.0 nm excitation. The active vibrational modes and the scattered intensity distribution are very different from those of the preresonance Raman spectrum of the $S_{1} (\pi - \pi^{*})$ $state.^{1}$ The observations will be compared to previous studies on benzene $^{2}$ and $pyrazine,^{3}$ and interpreted in terms of vibronic coupling. $^{1}$Y. Mochizuki, X. Kaya and M. Ito, J. Chem. Phys. 65, 4163 (1976); $^{2}$L. D. Ziegler and co-workers, J. Chem. Phys. 67, 2753 (1977); 68, 1248 (1978); $^{3}$I. Suzuka, Y. Udagawa and M. Ito, Chem. Phys. Letters 64, 333 (1979). $^{*}$Research supported in part by the U. S. National Science Foundatio