S1 and S2 States of Linear and Zigzag Cata-Condensed Hydrocarbons

We investigated the S-1 and S-2 states of linear and zigzag cata-condensed hydrocarbons on the basis of the results of jet spectroscopy and theoretical calculations. The S-1 states of anthracene and tetracene are represented by the HOMO -> LUMO configuration (Phi)(A)), whereas those of phenanthrene and chrysene are represented by HOMO-1 -> LUMO and HOMO -> LUMO+1 configurations (Phi(B)). We found that the fluorescence lifetime varied with different vibronic levels in the S-1 states of linear cata-condensed hydrocarbons due to the mode-selective internal conversion to the S-0 state. This selectivity is likely to be seen in the S-1 (Phi)(A)) state of the D-2h molecule.