H-1-O-17 NUCLEAR-QUADRUPOLE DOUBLE-RESONANCE STUDY OF RANDOM-FIELDS IN K-0.5(NH4)(0.5)H2PO4

The second moment [p(2)] of the local polarization distribution W(p) h as been measure in K-0.5(NH4)(0.5)H2PO4 as a function of temperature b y a H-1-O-17 nuclear-quadrupole double-resonance technique. The temper ature variation of [p(2)] is well described by a dynamic disorder of r andomly asymmetric O-H ... O hydrogen bonds. The variance Delta of the Gaussian distribution of random fields which induce the asymmetry of the O-H ... O hydrogen bonds is equal to (k(B) x 54 K)(2).