Electronic states of the phenoxyl radical

The phenoxyl radical and two of its isotopomers were investigated by UV-VIS and IR polarization spectroscopy of molecular samples immobilized in cryog enic argon matrices. Analysis of the combined electronic and infrared linea r dichroism data led to determination of absolute transition moment directi ons and symmetry assignments for four low-lying excited electronic states. The bands observed at 16 000, 25 200, 33 900, and 41 800 cm-1 were assigned to (2)A(1), B-2(1), (2)A(1), and B-2(1) pi-pi (*) states, respectively. A very weak transition observed in the near-infrared close to 8900 cm-1 was a ssigned to an optically forbidden B-2(2) n-pi (*) state. The electronic tra nsitions predicted by time dependent density functional theory (TD-UB3LYP/c c-pVTZ) were in good agreement with the observed transitions. (C) 2001 Amer ican Institute of Physics.