Abstract
Both absorption and luminescence spectra of a 2-(2, 4-dinitrobenzyl)pyridine dispersed in polymer films were measured in steady state at low temperature in order to elucidate the electronic states as well as the photochromic reaction accompanied with a proton transfer. Three absorption bands due to the photoproduct were observed in a visible region after the UV photolysis. Judging from the thermal behavior of these bands, the photoproduct consists of two different kinds of species (NH and OH forms), and the OH form thermally changes to the NH form. We also found that both the NH and OH forms optically return back to the colorless form (CH2 form) on the photolysis of visible light. The luminescence spectra due to the NH and OH forms were observed for the first time. The luminescence from the OH form has vibronic structures, while that from the NH form is broad without any vibronic structures. The shorter decay time of the luminescence in comparison with the estimated radiative lifetime suggests that the non-radiative relaxation process is responsible for the decay.
