Vibrational Spectroscopy and Relaxation in Liquids and Supercritical Fluids

麦迪逊的威斯康星州大学的James Skinner得到理论和计算化学计划的支持，以开发一个通用框架，在该框架内计算液体溶剂中溶质的时域和频域振动光谱。 这种方法建立在其他人的工作，其中的溶质和振动自由度的量子力学处理，和溶质的旋转和平移和所有溶剂的自由度的经典治疗。 该框架涉及重整化的溶质振动与溶剂的平均相互作用，因此预计能够描述系统与强溶质-溶剂相互作用。 理论方法将被应用到以下系统的实验已经进行：1）HOD在液体D2 O（振动光谱的OH伸缩），2）叠氮阴离子在液体D2 O（声子振动光谱的叠氮阴离子不对称伸缩），和3）超临界流体的氧气和氮气（拉曼光谱）。 最后，我们将研究多原子液体溶剂中溶质振动能弛豫的一些一般性问题。许多重要的工业和生物化学反应都发生在液体溶液中。 溶质分子周围溶剂分子的存在可以通过改变相对能级并提供有效能量流入和流出溶剂的途径来极大地影响化学反应的速率和机制。 该研究项目旨在从分子水平上解释溶剂对凝聚相中化学和生物过程的影响。

James Skinner of the University of Wisconsin, Madison, is supported by the Theoretical and Computational Chemistry Program to develop a general framework within which to calculate time- and frequency-domain vibrational spectra of solutes in liquid solvents. This approach builds on the work of others, where the solute and vibrational degrees of freedom are treated quantum mechanically, and the solute's rotations and translations and all solvent degrees of freedom are treated classically. The framework involves renormalization of the solute vibrations by the average interactions with the solvent, and so is expected to be able to describe systems with strong solute-solvent interactions. The theoretical approach will be applied to the following systems for which experiments have been performed: 1) HOD in liquid D2O (vibrational spectroscopy of the OH stretch), 2) the azide anion in liquid D2O (phonon vibrational spectroscopy of the azide anion asymmetric stretch), and 3) supercritical fluid oxygen and nitrogen (Raman spectroscopy). Finally, some general issues involving vibrational energy relaxation of solutes in polyatomic liquid solvents will be investigated.Many industrially and biologically important chemical reactions take place in liquid solution. The presence of solvent molecules are around a solute molecule can greatly affect rates and mechanisms of chemical reactions by changing the relative energy levels and providing pathways for efficient energy flow into and out of the solvent. This research project aims to provide a molecular level interpretation of the influence a solvent has on chemical and biological processes in condensed phases.