Raman spectra of low-lying longitudinal mode in KDP_1-xDKDP_x mixed crystals

Abstract

The D-concentration dependence of the low-lying z(xy)z mode (“L-mode”) spectra and z(xx)z mode (“R-mode”) spectra have been observed by a high contrast Raman spectroscopy in KDP_1-xDKDP_x ((KH₂PO₄)_1-x(KD₂PO₄)x) mixed crystals. In lower D-concentration region the “L-mode” spectrum shows a broad peak at ∼110 cm^-1 and the “R-mode” spectrum shows an over-damped feature. With the increase of D-concentration, the “L-mode” is reduced to an over-damped profile and the “R-mode” grows into a broad peak at ∼150 cm^-1. The results are briefly discussed in connection with the dynamical origin of the low-lying broad x(yx)y mode (“T-mode”) spectra