PHOTOCHEMICAL AND NON-PHOTOCHEMICAL HOLE BURNING IN DIMETHYL-S-TETRAZINE IN A POLYVINYL CARBAZOLE FILM

Hole burning as well as fluorescence line narrowing experiments have been performed on the system dimethyl-s-tetrazine in polyvinyl carbazole films at low temperatures. The first singlet electronic absorption bands are typical (300 cm{sup -1} wide) of inhomogeneously broadened bands of guest molecules in amorphous organic hosts. Evidence is presented for both photochemical and non-photochemical hole burning. The narrowest holes observed were Lorentzian, had a width 0.44 cm{sup -1} at 1.8 K, and are believed to be of non-photochemical origin. A model which envisions the guest molecules to occupy different sites in the polymer host with a distribution of energy barriers between sites is used to describe these observations. The fast (20 psec) relaxation time implied by the 0,44 cm{sup -1} Lorentzian linewidth is interpreted as indicative of the rate of site interconversion in the excited state