INFRARED-SPECTROSCOPY OF MATRIX-ISOLATED POLYCYCLIC AROMATIC-HYDROCARBONS - 2 - PAHS CONTAINING 5 OR MORE RINGS

Matrix isolation techniques have been used to measure the mid-infrared spectra of the polycyclic aromatic hydrocarbons (PAHs) benzo[e]pyrene , pentacene, perylene, benzo[ghi]perylene, coronene, and 1,12:2,3:4,5: 6,7:8,9:10,11-hexabenzocoronene. The observed band positions and rela tive strengths are compared to previous lab studies and with theoretic al calculations, where available.(1) Agreement with other available la boratory data is excellent. Comparisons with theory indicate that dens ity functional theory (DFT) does an excellent of describing the majori ty of the infrared active fundamentals of the PAHs considered here. Ba nd positions typically agree to better than 5 cm(-1), with the worst d isparities usually being less than 15 cm(-1). Matches in band strength s are not as precise, but are generally good to better than 30-50% for most strong and moderate bands and are good to factors of 2-4 for wea ker bands. The theory predicts CH stretching band strengths that are t oo strong by a factor of about 2.