The Ultraviolet Absorption of Simple Hydrocarbons IV. Unsaturated Cyclic Hydrocarbons in the Schumann Region

The absorption spectra of cyclohexene, cyclopentene, 1–3 cyclohexadiene and benzene have been examined in vapor phase in the region λ = 2300–1600A. The electronic excitation responsible for the first group of bands in this region is practically independent of the cyclic structure of the molecule since the wave number of the first band agrees closely with that obtained for olefins having the same arrangement of hydrogen-atoms around the double bond. Characteristic vibrational frequencies and different electronic levels have been identified.