Excited States of Flavins Characterised by Absorption, Prompt and Delayed Emission Spectra

The angles between the two principal long wavelength absorption oscillators of FMN and some other flavins have been measured by two methods. A novel technique involving dichroic bleaching gave a value (approx. 35°) consistent with that obtained from the polarisation of fluorescence extrapolated to infinite viscosity. Flavins trapped in polyacrylamide films display E‐type delayed fluorescence and phosphorescence depending on the temperature. The variations in lifetimes and intensities of these two delayed emissions with temperature have been studied. The Arrhenius activation energies have been analysed in terms of a scheme that gives information about the interrelationships between different electronic states of flavins.