Raman Spectrum of the Phenyl Radical

The Raman spectrum of phenyl radical (C6H5) isolated in low-temperature argon matrices has been obtained. The assignments of experimentally observed frequencies are based on comparison with results of quantum chemical calculations (B3LYP/cc-pVTZ) and with infrared absorption bands measured for 12C6H5 and 13C6H5 species. Analysis of the IR and Raman spectra, including IR linear dichroism, and of the isotopic shifts caused by 12C → 13C substitution allows to reconfirm most of the previous assignments and to introduce some corrections. The prominent ring breathing mode, characteristic for benzenoid compounds (991 cm-1 in benzene), occurs in phenyl radical at 998 cm-1.