Abstract
Relaxation due to incoherent tunnelling is shown to be responsible for the anomalous temperature dependence of the homogeneous linewidth of optical transitions in glasses. The distribution function of the tunnelling model for the parameters of the tunnelling systems (TS) is used, and dipole-dipole coupling between the chromophore and the TS is assumed. Within this, a bending from a linear to a quadratic temperature dependence of the homogeneous linewidth at T* ≈ 5 K is derived. Measurements on SiO2, GeO2 and BeF2 doped with Eu3+ and Pr3+ are quantitatively accounted for by our theory. This interpretation is supported by acoustic measurements on oxide glasses.
Published Version
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