Electronic Spectrum of Ethylene Single Crystal; Search for the Olefin Mystery Band

Ethylene single crystals have been grown as uv specimens. The near-uv spectrum (2000–2500 Å) consists of a number of bands quite analogous to the π—π* (N–V) transition in the gas-phase molecule. No drastic perturbations are observed. No additional electronic transition (e.g., CH*—π, n—π*) is observed in this region, in spite of the relaxation of selection rules in the crystalline site (Ci). Thus, if the ``mystery'' band (6 eV) exists at all, its excited state is most likely either a triplet state or a Rydberg-type state (or a combination of both).