Anomalous spectral diffusion in polymer glasses

Spectral diffusion (SD) in PMMA samples, doped with Zn-tetrabenzoporphyne, was investigated via populational hole burning in the absorption spectrum of a chromophore on a time scale 20 μs–150 ms and in a temperature interval of 1.7–10 K. An anomalous increase of the SD rate was found in the millisecond range, which cannot be attributed to peculiarities in the relaxation rate distribution of the two-level systems in PMMA. The apparent correlation of the anomalous SD region with the time domain of chromophore triplet state deactivation cannot be explained in the framework of existing SD models.