LASER-INDUCED FLUORESCENCE SPECTROSCOPY OF JET-COOLED BENZOPHENONE KETYL RADICAL

The D-1 <-- D-0 transition of jet-cooled benzophenone ketyl radical (B PK) and its deuteride was studied by using laser-induced fluorescence (LIF) spectroscopy. BPK was generated by the 248 nm photolysis of alph a-phenylbenzoin, and its vibrationally resolved LIF excitation and emi ssion spectra were obtained for the first time. The 18 451 cm(-1) band was assigned to the 0(0)(0) band of the D-1 <-- D-0 transition of BPK . Two vibrational modes of BPK with 65 and 84 cm(-1) in the first exci ted state were assigned to the in-phase and out-of-phase torsional mot ions of the phenyl rings, respectively. The vibrational mode with 980 cm(-1) was tentatively assigned to the C-O stretching mode. The mode o f 74 cm(-1) in the ground state was assigned to the in-phase torsional mode. It was confirmed that the torsional motions do not couple with the C-O stretching and O-H rotational motions. The force field analysi s and the simple Franck-Condon calculation were made. The measured flu orescence lifetimes of BPK and its deuteride are short and consistent with those in the gas and liquid phases at room temperature.