Microscope models of guest molecular vibrations in crystalline and glass hosts

Uebbing and Sievers [Phys. Rev. Lett. 76, 932 (1996)] have shown with time-resolved saturation spectroscopy that the nonradiative decay rate γ of internal guest high-frequency H₂O symmetrical stretching vibrations in soft ternary Ge-As-Se host glasses is a function only of $〈r〉$, the average host coordination number. A theoretical model based on the constraint theory of the structure of these network glasses explains the observed functional dependence, which is broadly linear with a break in slope at $〈r〉=2.4$. The theoretical model also explains the width and asymmetry of the remarkable cusp which occurs in γ(〈r〉) at $〈r〉=2.4$.