Electronic absorption spectrum of phenyl radical

The electronic absorption spectrum of matrix-isolated phenyl radical has been determined in the entire 52 000–4 000 cm−1 region. It consists of three band systems corresponding to transitions to three excited electronic states: 2B1, with origin at 510.5 nm/2.43 eV (ε=2.8 L mol−1 cm−1); 2A1, with λmax=235.1 nm/5.27 eV (ε=220 L mol−1 cm−1), and 2B2 with the origin at 211.5 nm/5.86 eV (ε=1650 L mol−1 cm−1). These transitions are attributed to the phenyl radical on the basis of the strict correlation of their intensity evolution in simultaneously measured IR and UV–visible spectra. Consistent results were obtained from several independent precursors. The transition symmetries were derived from polarization measurements on photo-oriented samples.