Structural relaxations in amorphous water studied by hole-burning spectroscopy

The annealing behavior of dye-doped amorphous water below its glass transition temperature was investigated by means of spectral hole-burning and IR spectroscopy. The dye molecules act, at low concentration, as optical probes of the water matrix. Measurements of the time-resolved spectral diffusion of spectral holes confirm that the narrowing of the quasi-homogeneous linewidth observed upon annealing is due to a reduction of the number density of two-level systems. Further information is gained from temperature cycling experiments. The results strongly indicate a transformation from a fragile to a strong glass by the formation of an H-bond network.