| Abstract: | Infrared absorption spectra of the CH stretching region were observed for naphthalene, anthracene, phenanthrene, pyrene, and perylene using a heated, supersonic, slit‐jet source and cavity ringdown spectroscopy. Band positions and intensities recorded with 0.2‐cm?1 resolution were compared with previous gas‐phase and argon matrix isolation experiments, as well as theoretical calculations. The largest matrix shift in the absorption maximum (‐7.4 cm?1) was observed for anthracene, with all others shifted by 3.0 cm?1 or less. Spectral features in the supersonic jet spectrum were generally narrower than those observed in the Ar matrix, with the largest matrix broadening found for the perylene (80 % increase). Low number densities observed for the larger polycyclic aromatic hydrocarbons (PAHs) suggest that the lower vapor pressure of PAHs with catacondensed four‐membered rings and with five‐membered rings other than perylene will not be detectable using our current configuration. |
