Measuring the conformational properties of 1,2,3,6,7,8-hexahydropyrene and its van der Waals complexes.

Rotationally resolved fluorescence excitation spectra of the S(1)<--S(0) origin band transitions of two conformers of 1,2,3,6,7,8-hexahydropyrene (HHP) have been recorded in the gas phase. The band at 30,648.0 cm(-1) has been assigned as the origin band of the chair conformer and the band at 30,658.8 cm(-1) has been assigned as the origin band of the boat conformer on the basis of differences in their rotational constants. In addition, rotationally resolved fluorescence excitation spectra of single Ar and H(2)O van der Waals complexes of chair-HHP have been observed. Analyses of these results indicate that the weakly attached argon atom (water molecule) is located on top of the plane of the bare molecule at approximately 3.4 A (approximately 4.1 A) from its center of mass in the S(0) electronic state. No complexes of boat-HHP were detected.