DIRECT ABSORPTION-SPECTRA OF JET-COOLED BENZENE IN 130-260-NM

The direct absorption spectrum of benzene in a free jet has been measured in the 130-260 nm region (S1, S2, and S3 states, Rydberg series, and the first ionization limit) using synchrotron radiation as a light source. The absolute molar extinction coefficients (epsilon) of benzene in jets have been determined by scaling measured free-jet values to the known value in the vapor phase for a broadband at 200.1 nm in the S2 state. The vibrational temperature for nu-16 mode was estimated to be 185 K. The maximum value of epsilon of the S1 absorption system was found to be 1400 l mol-1 cm-1 (spectral bandwidth = 0.065 nm). A shoulder observed at 205.45 nm in the S2 absorption system is assigned to the S2 origin, induced by pseudo-Jahn-Teller distortion.