| Abstract
| - Calculations are carriedout using density functional theory (DFT)to determine the harmonic frequenciesand intensities of perdeuterated naphthalene, phenanthrene, pyrene,andchrysene. We also report matrix-isolation spectra for these four species.The theoretical andexperimental frequencies and relative intensitiesfor the perdeuterated species are in generally good agreement. Theeffect of perdeuteration is to reduce thesum of the integrated intensities by a factor of about 1.75. Thisreduction occurs for all vibrational motions,except for the weak low-frequency ring deformation modes. There isalso a significant redistribution of therelative intensities between the out-of-plane C−D bands relativetothose found for the out-of-plane C−Hbands. The theoretical isotopic ratios provide an excellentdiagnostic of the degree of C−H(C−D) involvementin the vibrational bands, allowing in most cases a clear distinctionofthe type of motion.
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