Abstract

A photochemical hole, burnt into the lowest absorption band of quinizarin in an alcohol glass, was used as an optical detector for structural relaxation processes of the glass. The hole burning photochemistry is due to a light induced breakage of an intramolecular hydrogen bond between the dye molecule and the solvent (1). The stability of the photoproduct is determined by the local conformation of the solvent cage. Hence, one expects a wide distribution of back transfer rates R from the product to the reactant state. As a probe for the number of relaxed molecules we use the area of the photochemical hole. Fig.1 shows the normalized hole area as a function of probing time. The recovery dynamics of the hole occurs on a logarithmic time scale and is subject to a remarkable deuteration effect. In a similar way, the width of the optical transition increases on a logarithmic time scale. To find a quantitative interpretation of the measured logarithmic slopes we introduced the concept of photochemically induced tunnel systems. We consider the product and the educt state as a special two level system, with a distribution of tunneling rates R given by the well known distribution of the TLS states of glasses (2, 3).

© 1984 Optical Society of America