Spectral assignment of dual conformers of 1,2,3,6,7,8-hexahydropyrene in the supersonic jet

Abstract

The laser-induced fluorescence excitation (FE) spectra of 1,2,3,6,7,8-hexahydropyrene has been observed in jet-cooled condition. The FE spectrum show the existence of interconvertible conformers, chair and boat, with 0-0 bands 12 cm^-1 apart. On the basis of semiempirical calculations and single vibronic level luminescence, the longest wavelength band at 30653 cm^-1 has been ascribed to chair conformer and the one at 30665 cm^-1 to the boat conformer. The low-frequency vibronic bands have been tentatively assigned. The lifetimes of low-frequency vibronic levels follow the trend reported by Jacobson et al. [J. Chem. Phys. 87, 269 (1987)] for naphthalene monoderivatives, namely, they fluctuate at low excess energies, but merge and decrease steadily at high energies of excitation.