手性分子非线性和频光谱的理论研究

手性对生命、医学、物理与化学等领域有重大的影响。近几年，随着科学的发展，和频谱成为研究与表征界面与体相分子手性的强有力的手段。传统的手性谱只能研究分子在气体、液体和固体等体相的结构，对界面取向不敏感，而手性和频谱不仅可以研究分子在体相的结构而且可以研究分子在界面的取向结构。手性谱实验研究可以得到分子的官能团，但很难得到分子的绝对结构，而理论计算研究可以得到分子的结构。结构决定性质，理论上在结构基础上得到的波函数或电子密度可以研究分子的一切性质和相互作用。我们将探讨费米共振对体相手性分子的影响，找到决定手性体相信号的决定因素；探讨手性超分子与手性聚集体倍频谱，揭示它们在界面的取向结构以及单体间的相互作用；讨论氨基酸与多肽的和频谱，发现它们二级结构与光谱之间的关系以及多肽在生物膜界面的结构与相互作用。这些研究有助于进一步深入理解手性分子在界面与体相的结构和非线性和频谱的内在机理。

Chirality is very important in life, medicine, physics and chemistry. In recent years, with the development of science, sum-frequency spectroscopy has become a powerful method to study the chirality at interfaces and in the bulk. Chiral spectra such as circular dichroism spectroscopy, optical rotation spectroscopy and Raman optical activity spectroscopy can only study the molecular structure in gas, liquid and solid phases, and are insensitive to orientation at interfaces. Chiral sum-frequency spectroscopy can not only study the molecular structure in the bulk but also investigate the molecular orientation at interfaces. The experimental studies of chiral spectra can only discover the molecular functional groups, but can not obtain the absolute molecular structure, and the theoretical computations can get the molecular structure. The structure determines the molecular properties. Theoretically, the wavefunctions or the electron densities obtained based on the structure can study all the properties and the interactions of molecules, which are the advantages of theoretical calculations. Using theoretical and computational study, we will study the influence of Fermi resonance on the chiral molecules and find the dominant cause of the chiral signals; we shall explore the second harmonic generation for supramolecular and aggregate chirality and and reveal the orientation structure at interfaces and the interactions between the monomers; we will discuss the sum-frequency spectroscopy for amino acids and peptides and obtain the relationship between the secondary structure of polypeptide and the spectroscopy and the structure and the interaction of polypeptide on the biomembrane surface. These studies are helpful to understand the structure of chiral molecules at interfaces and in the bulk and the intrinsic mechanism of the nonlinear sum-frequency spectroscopy.