The infrared spectrum of the matrix-isolated phenyl radical

We have measured the infrared absorption spectrum of C6H5, (X) over tilde ( 2)A(1), in an Ar matrix at 10 K. The experimental frequencies (cm(-1)) and polarizations follow, a(1) modes: 3086; 3072, 3037, 1581, 1441, 1154, 1027, 997, 976, 605;b(1) modes: 972, 874, 706, 657, 416; b(2) modes: 3071, 3069, 1624, 1432, 1321, 1283, 1 159, 1063, and 587. Three different methods have been used for the production of the phenyl radicals. Infrared absorption s pectra of five deuterated isotopomers, C6D5, p-C6H4D, p-C6HD4, o-C6H4D, and m-C6H4D, were recorded to compare experimental frequency shifts with calcu lated (UB3LYP/cc-pVDZ) harmonic frequency shifts. The use of CO2 or NO as i nternal standards enabled the experimental determination of absolute infrar ed intensities. The linear dichroism was measured with photooriented sample s to establish experimental polarizations of each vibrational band. True ga s-phase vibrational frequencies were estimated by considering the gas-to-ma trix shifts and matrix;inhomogeneous line broadening. The phenyl radical ma trix frequencies listed above are within +/-1% of the gas-phase vibrational frequencies. The C6H5 frequencies from this paper supersede our earlier va lues reported in J. Am. Chem. Soc. 1996, 118, 7400-7401.