Knowledge Bank

Spectroscopic investigations on cyclooctatriene in solution and in the condensed phase at reduced temperatures have shown no observable emission. We report the observation of emission produced by exciting cyclooctatriene seeded in a supersonic helium expansion. The excitation spectrum for this emission has been measured from $34,140cm-1$ to $37,500cm-1$. The lowest energy feature is at $34,785cm-1$. Dispersed emission spectra for excitation at a number of vibronic bands in the excitation spectrum have also been measured. Irradiation of cyclooctatriene vapor efficiently produces all trans, octatetraene. Taken together, these measurements make a case for photochemical rearrangement in the isolated molecule.