Opto‐thermal spectroscopy of the benzene 4←0 C–H stretch overtone

The 4←0 C–H stretching overtone of benzene has been measured in a supersonic molecular beam by means of the opto‐thermal technique. Several vibrational transitions contribute to the absorption spectrum in the 11 400–11 550 cm−1 region. The upper limit for the homogeneous linewidth is found ≊17 cm−1.