Anomaly of the Raman Linewidth of the Internal u₂ Mode near the Phase Transition Point of K₃D(SO₄)₂

Abstract

The linewidth of the internal mode ν ₂ of SO₄^2- ion of the antiferroelectric K₃D(SO₄)₂ shows the anomalous broadening with lowering temperature near the phase transition point. The broadening is well explained by a mechanism resembling the motional narrowing phenomenon in the nuclear magnetic resonance theory. The characteristic time of the motion of deuteron in a hydrogen bond is estimated to be on the order of 10^-13, s.