An experimental investigation was made of the face-centered cubic lattice-defect system of Ag+-doped material. It showed that a thermally activated disappearance of the strengths of the infra-red and Raman active vibrational modes, and the appearance of radio-frequency dispersion and frequency-shifted ultra-violet electronic transitions, were associated with Ag+ ions moving from an on-center to an off-center configuration. The possibility of an impurity/intrinsic localized-mode complex dissociating so as to produce the rapid temperature dependence was tested. However, the absence of a concentration dependence of the normalized vibrational mode strengths as a function of temperature, appeared to rule this trapping model out. A jump rotational-diffusion model could explain the observed results in terms of 2 elastic configurations which were separated by a high energy barrier. The impurity jumped between the configurations, with temperature-dependent dwell-times.

Vibrational Dynamics Associated with Multiple Elastic Configurations in KI:Ag+. A.J.Sievers, R.Lai: Physica D, 1998, 119[1-2], 205-18