In this work

the absorption and fluorescence spectra of dibenzoyl methane have been studied. The structure of dibenzoly. methane is different from o-hydroxybenzophenones and o-hydroxyphenylbenzotriazoles. It has two absorption peaks at 252 nm and 340 nm as well as o-hydroxy-p-octyloxy benzophenone. The absorption at 340 nm is concerned with the formation of . intramolecular hydrogen bond. It has been found that an uncommonly large Stoke's shifts of fluorescence can be observed. The photostabilizing effect of dibenzoyl methane and o-hydroxy-p-octyloxy benzophenone on the photodegradation of cis-1

4-polybutadiene has been investigated for comparison. Its photostabilizing effect is similar to o-hydroxy-p-octyloxy benzophenone.Possible mechanism was discussed.