Excitation and emission spectra of polyethylene terephthalate and polyethylene 2,6-naphthalate films

With excitation by the light of the wavelengths longer than 320nm, fluorescence spectra of polyethylene terephthalate (PET) films had somewhat different shapes from those excited below 300nm through the intrinsic absorption of PET molecules. Also, in the measurements taken with a polarizer in front of the receiving mono-choromator but none before the sample, the intensity ratio of parallel (to the draw axis of the film) and perpendicular components of the emission spectra was different if excited above 320rzm or below 300nm. Discussion was made about the first step of pumping photon energy at the wavelengths above 320nm. Fluorescence spectra of polyethylene 2,6-naphthalate films showed a mirror image of their absorption spectra, consisting of one broad band having the same polarization as their absorption spectra. Their fluorescence occurred from the lowest excited level, conforming to the Kasha law. Copyright (C) 1999 John Wiley & Sons, Ltd.