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

The laser-induced fluorescence excitation (FE) spectra of 1,2,3,6,7,8-hexah ydropyrene has been observed in jet-cooled condition. The FE spectrum show the existence of interconvertible conformers, chair and boat, with 0-0 band s 12 cm(-1) apart. On the basis of semiempirical calculations and single vi bronic level luminescence, the longest wavelength band at 30 653 cm(-1) has been ascribed to chair conformer and the one at 30 665 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 b y Jacobson [J. Chem. Phys. 87, 269 (1987)] for naphthalene monoderivatives, namely, they fluctuate at low excess energies, but merge and decrease stea dily at high energies of excitation. (C) 2001 American Institute of Physics .