Departamento de Física, ICEx, Universidade Federal de Minas Gerais, C.P. 702, Belo Horizonte, MG 30123-970, Brazil.
LPEM, ESPCI Paris, PSL Research University, CNRS, F-75005 Paris, France; Sorbonne Universités, Univ. Paris 6, CNRS, LPEM, F-75005 Paris, France.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jan 5;188:276-284. doi: 10.1016/j.saa.2017.07.017. Epub 2017 Jul 14.
A comprehensive set of optical vibrational modes of monoclinic taurine crystals was determined by Raman scattering, and infrared reflectivity and transmission spectroscopies. By using appropriate scattering/reflection geometries, the vibrational modes were resolved by polarization and the most relevant modes of the crystal could be assigned. In particular, we were able to review the symmetry of the gerade modes and to resolve ambiguities in the literature. Owing to the non-orthogonal character of B modes in monoclinic crystals (lying on the optic axial plane), we carried out a generalized Lorentz dispersion analysis consisting of simultaneous adjust of infrared-reflectivity spectra at various light polarization angles. The A modes (parallel to the C-axis) were treated within the classical Lorentz model. The behavior of off-diagonal and diagonal terms of the complex dielectric tensors and the presence of anomalous dispersion were discussed as consequences of the low symmetry of the crystal.
通过拉曼散射、红外反射率和透射光谱学，确定了单斜型牛磺酸晶体的一套完整的光学振动模式。通过使用适当的散射/反射几何形状，通过偏振来分辨振动模式，并对晶体的最相关模式进行了分配。特别是，我们能够回顾正则模式的对称性，并解决文献中的歧义。由于单斜晶体中 B 模的非正交性质（位于光轴平面上），我们进行了广义洛伦兹色散分析，包括在各种光偏振角下同时调整红外反射光谱。A 模（平行于 C 轴）在经典洛伦兹模型中进行处理。讨论了复介电张量的非对角和对角项的行为以及异常色散的存在，这是晶体低对称性的结果。
