抄録
Low frequency E(x, y)-mode Raman spectrum of a KH2PO4 crystal is discussed in terms of the pseudo-spin model extended by Havlin et al. to the problem of transverse susceptibility. Temperature dependence of the susceptibility obtained from the integrated intensity of a broad continuum of the Raman spectrum can be well interpreted by their theory. The theory indicates that this mode, just like the B2(z)-soft phonon mode, originates from a zone-center phonon corresponding to a collective proton motion in the a-b plane. Dynamics of the E-mode is also discussed in the framework of the pseudo-spin formalism and it is shown that this model is applicable not only to B2(z) soft mode but also, at least qualitatively, to the E(x, y) mode in spite of the apparently different behaviour of the two modes with respest to the phase transition.
