INFRARED-SPECTRA OF PERDEUTERATED NAPHTHALENE, PHENANTHRENE, CHRYSENE, AND PYRENE

Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of perdeuterated na phthalene, phenanthrene, pyrene, and chrysene. We also report matrix-i solation spectra for these four species. The theoretical and experimen tal frequencies and relative intensities for the perdeuterated species are in generally good agreement. The effect of perdeuteration is to r educe the sum of the integrated intensities by a factor of about 1.75. This reduction occurs for all vibrational motions, except for the wea k low-frequency ring deformation modes. There is also a significant re distribution of the relative intensities between the out-of-plane C-D bands relative to those found for the out-of-plane C-H bands. The theo retical isotopic ratios provide an excellent diagnostic of the degree of C-H(C-D) involvement in the vibrational bands, allowing in most cas es a clear distinction of the type of motion.