Evolution of Spectral Holes on Logarithmic Time Scales

Abstract

Persistent spectral holes are extremely sensitve probes for long time tails in the relaxation patterns of amorphous solids. We succeeded recently in measuring the time evolution of photochemical and photo-physical holes in alcohol glasses at temperatures around 1K /1,2/. The photoactive probe molecules were 1,4 dihydroxyanthraquinone (DAQ) and tetracene (T). In alcohol glass, DAQ undergoes a light induced proton transfer reaction, whereas the detailed nature of the phototransformation of T in alcohol glass is not known (for a recent review see /3/). We measured the area of the holes, their width, their shape and their degree of polarization /4/. The experimental observation period was 1 week. The results can be summarized as follows: 1) the area A(t) decreases linearly on a logarithmic time scale (Fig. 1) 2) the width increases linearly on a logarithmic time scale (Fig. 3) 3) in deuterated glass, the relaxation processes occur on a time scale which is orders of magnitudes slower (Fig. 1 and Fig. 3) 4) the degree of polarizsation remains constant (Fig. 1 and Fig. 2) 5) the photochemical (DAQ) and the photophysical (T)-system show similar relaxation patterns (Fig. 1 and Fig. 2).