Anomalous epr lineshapes for AsO₄⁴ center in NH₄H₂PO₄-RbH₂PO₄ glasses: Strain VS dynamic effects

Abstract

The temperature dependence of lineshapes of EPR signals of AsO₄ ⁴ center has been utilized as a probe of the slow dynamics of (NH₄H₂PO₄)_x-(RbH₂PO₄)_1–x proton glass system over the whole composition range x. The EPR signals exhibit anomalous line-broadening as a function of x as well as temperature. A theoretical procedure was developed based on the formalism of modified Bloch equations, that enabled us to evaluate the broadening effect of motional dynamics, and, consequently, lattice strain. A comparison of the experimental and theoretical lineshapes revealed that strain broadening, and not exchange effects, makes a dominant contribution to the broadening of EPR signals in the proton glass.