(all‐E)‐1,3,5,7‐Octatetraene: Electron‐Energy‐Loss and Electron‐Transmission Spectra

Abstract
Electron‐energy‐loss and electron‐transmission spectra of (all‐E)‐1,3,5,7‐octatetraene were recorded with a trochoidal electron spectrometer. The energy‐loss spectra reveal two triplet states at 1.73 and 3.25 eV (0,0‐transitions), the UV‐active 11Bu state at 4.40 eV, and a higher‐lying singlet state at 6.04 eV. The 21Ag state recently reported to be the lowest excited singlet state in this polyene, could not be observed. This failure is probably de to a small excitation cross section under the scattering conditions used and the presence of the second triplet sate in the pertinent energy region. The electron‐transmission spectrum revealed three resonances (i.e. short‐lived anion states) at 1.5, 2.5, and 4.15 eV.