Theory of Transient, Collision-Induced Changes in Molecular Dipoles and Polarizabilities

这个物理化学项目的重点是在分子碰撞的时间尺度上，从理论上确定分子偶极子和极化率的瞬态、相互作用引起的变化。在相互作用分子之间的重叠很小的地方，计算将基于PI的非局部极化密度模型，该模型考虑了可极化物质在每个分子中的分布。该模型将被扩展为包括计算非局部非线性响应的实用手段。将对物理含量的极化密度进行分析，并计算光谱感兴趣的碰撞诱发性质。PI还将首次应用反应场理论来发现各向异性分子极化的色散贡献，并将该理论扩展到频率相关响应。为了纳入重叠适中的非加性交换极化，PI计划执行密度泛函和交换摄动计算；后者还包括电荷转移。所需的单分子矩，磁化率和短程对性质将由从头计算确定。待研究的代表性物种包括H2…H2, N2……N2,基于“增大化现实”技术的…Ar和HCl。该研究对于其光谱应用具有重要意义，因为如果确定了两个碰撞诱导的偶极子和极化率是分子间距离、相对取向和振动频率的函数，则可以从碰撞诱导的吸收和散射光谱中提取分子间动力学的重要信息。

This project in the physical chemistry program focuses on the theoretical determination of transient, interaction-induced changes in molecular dipoles and polarizabilities on the time scale of molecular collisions. Where overlap between the interacting molecules is slight, calculations will be based on the PI's nonlocal polarizability density model, which accounts for the distribution of polarizable matter throughout each molecule. The model will be extended to include a practical means of computing nonlocal, nonlinear response. The polarizability densities will be analyzed for physical content, and collision-induced properties of spectroscopic interest will be computed. The PI will also apply reaction field theory to find dispersion contributions to the polarizabilities of anisotropic molecules for the first time, and extend the theory to frequency-dependent response. To incorporate nonadditive exchange-polarization where overlap is moderate, the PI plans to perform density functional and exchange-perturbation calculations; the latter also include charge transfer. Required single-molecule moments, susceptibilities, and short-range pair properties will be determined by ab initio calculations. Representative species to be studied include H2...H2, N2...N2, Ar...Ar, and Ar...HCl. This research is important for its spectroscopic applications, since significant information on intermolecular dynamics can be extracted from collision-induced absorption and scattering spectra, if the two collision-induced dipoles and polarizabilities have been determined as functions of intermolecular distances, relative orientations, and vibrational frequency.