Rotationally resolved UV spectroscopy of room temperature benzene by sub-Doppler degenerate four-wave mixing

Rotationally resolved room temperature spectra of the 601101, S1⌉S0 electronic one-photon transition of geseous benzene have been measured using degenerate four-wave mixing (DFWM) spectroscopy with narrow band Fourier transform limited UV light pulses. In ‘forward box’ geometry a resolution of 750 MHz was obtained, which is half the Doppler-width. In ‘backward box’ geometry the achieved resolution is 100 MHz. Despite the nonlinear character of DFWM the rotational features can be fit to a symmetric top model using assigned transitions up to J′ = 50, demonstrating the usefulness of DFWM spectroscopy for determination of rotational constants.