旋光性单轴晶体的喇曼光谱中TO和LO模的识别

本文提出一种简便识别旋光性单轴晶体喇曼光谱中横模和纵模的方法。应用90°散射几何配置x(z+Δy,xz)y,散射光的偏振方向与x轴成δ夹角。应用Loudon给出的单轴晶体极性声子的喇曼散射效率公式,计算TO和LO模的散射效率,它们依赖于喇曼张量元和δ角,其极大值分别位于δ_max^TO和δ_max^LO处,这两个角度的符号正好相反。因此,由判定δ_max的符号,可以将TO和LO模区分开来,并且从|δ_max|值可以了解喇曼张量的各向异性。关键词：

DISTINGUISHING THE TO AND LO MODES OF RAMAN SPECTRA IN OPTICAL ACTIVITY UNIAXIAL CRYSTALS

A simple method to distinguish the TO and LO modes of Raman spectra in optical active uniaxial crystals was proposed in this paper. Using 90°scattering geometry configuration x(z+△y, xz)y, the angle between polarization direction of scattering light and x axis is denoted by δ. Applying the formula of Raman scattering efficiency of polar phonons in uniaxial crystal given by Loudon, we found that scattering efficiencies of TO and LO modes depend on components of Raman polarizability tensor and angle d. If δ_max^TO and δ_max^LO represent the angles at which Raman scattering efficiencies for TO and LO modes take maximum value respectively, it turns out that sign of δ_max^TO and δ_max^LO is just opposite. Therefore, according to sign (δ_max), TO and LO modes can be distinguished, and anisotropy of Raman tensors can be extracted from the absolute values of δ_max.