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 (ε) 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 ν16 mode was estimated to be 185 K. The maximum value of ε 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.