Optical Properties of Six-Member Carbon Ring Organic Liquids in the Vacuum Ultraviolet

Optical data for incident photon energies 2.0–10.6 eV are reported for 1,3‐cyclohexadiene, cyclohexene, and cyclohexane in the liquid state. New measurements of the optical constants of liquid benzene over this energy region are included for comparison. An interpretation of the data is made in terms of molecular excitations of $\pi$ and $\sigma$ electrons and collective oscillations of the electrons in the liquids.