Neutron scattering study of NH₄- and acid proton "freezing" in Rb_1-x(NH₄)_xH₂PO₄

We have studied the "freezing" of the proton degrees of freedom in the structural glass Rb1-x(NH4)xH2PO4 (RADP) by means of incoherent neutron scattering. The elastic incoherent structure factor (EISF) for the NH4-reorientations has been determined. Three regimes are observed for the temperature dependence of the fixed window intensity. Their connection with NMR-measurements, X-ray- and Raman scattering, is discussed. © 1989.