FLUORESCENCE AND ULTRAVIOLET ABSORPTION SPECTRA AND RING-TWISTING POTENTIAL ENERGY FUNCTIONS OF 1,2-DIHYDRONAPHTHALENE IN ITS $S_{0}$ AND $S_{1}$ STATES

Author Institution: Department of Chemistry, Texas A\&M UniversityThe fluorescence excitation spectra (FES), dispersed fluorescence (SVLF) spectra, and ultraviolet absorption spectra of 1,2-dihydronaphthalene have been collected and analyzed. The $S_{1}(\pi,\pi^{\ast})$ electronic band origin is at $34,096 cm^{-1}$. The FES for the jet-cooled molecules shows the four lowest frequency vibrations in the $S_{1}$ state to be at 107, 122, 197, and $293 cm^{-1}$; while the SVLF from several excitation bands shows these to be at 131, 149, 267 and $347 cm^{-1}$ in the $S_{0}$ state. For both states almost all of the transition frequencies below $800 cm^{-1}$ can be assigned as combinations of these low-frequency modes. The series of bands beginning with $131 cm^{-1}$ for $S_{0}$ and $122 cm^{-1}$ for $S_{1}$ were analyzed to determine the ring-twisting potential energy functions. For the $S_{0}$ state the barrier of about $1300 cm^{-1}$ is somewhat higher than that ($1132 cm^{-1}$) for the analogous molecule 1,3-cyclohexadiene. For the $S_{1}$ state the barrier increases significantly