Lowest excited triplet state of naphthalene, by transient polarized resonance Raman, matrix-isolation infrared, and density-functional-theory methods

Transient polarized resonance Raman spectra of naphthalene and its fully de uterated species in the lowest excited triplet state were measured. An anal ysis of the depolarization ratios showed that all the observed bands were a ssignable to the ag vibrational modes. Matrix-isolation infrared spectra of the excited state [J. Mel. Struct. 1999, 475, 253] were remeasured to obse rve further bands with weak intensities. The DFT (density functional theory ) calculation was also performed to confirm the vibrational assignments, wh ere the 6-31G* basis set was used to optimize the geometrical structure. Th e DFT calculation is found to be useful to predict the vibrational wavenumb ers of the lowest excited triplet state as well as the ground singlet state of this molecule.