Supersonic jet-cooled laser-induced fluorescence(LIF) spectrum of biacetyl

The laser-induced fluorescence (LIF) excitation spectra of biacetyl in the range of 432-451 nm were obtained under the supersonic jet condition. Three weaker peaks, which are at 0, 87 and 98 cm(-1), respectively (related to 2 2 182 cm(-1)) were observed in a high sensitivity spectrum at red-hand of 2 2 336 cm(-1) peak which was assigned as band origin previously, The tunnel splits for 87 and 97 cm(-1) peaks were observed in the hyperfine spectra, T hey are 1.04 cm(-1) and 1.68 cm(-1) for 87 cm(-1) peak and 97 cm(-1) peak r espectively, These values are in agreement with calculated values very well . The band origin of S-1<--S-0 transition is now determined at 22 182 cm(-1 ), A complete assignment of biacetyl LIF spectrum is done for the first tim e, The frequency of torsion mode is determined to be 91.1 cm(-1), and the e nharmonic constant is 4.875 cm(-1).