Dielectric relaxation of interacting hydroxyl ions in KCl crystals

We report low-temperature measurements of the dielectric susceptibility and dielectric absorption of OH- and OD- defects in potassium chloride crystal s. With rising concentration mutual interaction between the defects leads t o a cross-over from coherent to incoherent tunnelling, which in turn change s the energy spectrum and the dynamics of the defects. In addition, we have studied the dielectric absorption arising from the thermally activated reo rientation of well-defined defect pairs. (C) 1999 Elsevier Science B.V. All rights reserved.