Toward a Molecular Understanding of Quantum Chemical Dynamics in Solution

保罗·芭芭拉得到了理论和计算化学计划的资助，继续他的理论和实验研究，旨在了解溶液中的量子化学动力学。利用飞秒泵浦-探测光谱学作为实验工具，Barbara将研究：1)对称和不对称金属-金属价间化合物中的电子非绝热跃迁；2)碘水溶液中单光子和双光子电离以及水的双光子电离中的电子非绝热跃迁；3)DNA中强溶剂化小自由基的光解离、复合和振动弛豫中的振动非绝热跃迁；以及4)DNA中金属插层剂之间可能存在的长程相干电子转移。对现有的电子转移和振动弛豫的量子理论模型进行了理论研究。由于许多重要的商业化学反应都是在水等极性溶剂中进行的，因此了解这些溶剂对反应动力学的影响是很重要的。溶剂笼效应、振动弛豫和量子力学隧道效应等在气相中不存在的效应完全主导了凝聚相化学反应。重要的是要建立可靠的化学体系模型理论，然后将其用于提高具有重要商业意义的化学反应的效率。芭芭拉正在进行的工作为这些理论的发展提供了重要的实验基础。

Paul Barbara is supported by a grant from the Theoretical and Computational Chemistry Program to continue his theoretical and experimental research directed at understanding quantum chemical dynamics in solution. Using femtosecond pump-probe optical spectroscopy as an experimental tool Barbara will study: 1) electronically nonadiabatic transitions in symmetric and asymmetric metal-metal intervalence compounds; 2) electronically nonadiabatic transitions in the one and two photon ionization of aqueous iodide solution and the two photon ionization of water; 3) vibrationally nonadiabatic transitions in the photodissociation, recombination, and the vibrational relaxation of small strongly solvated radicals with high frequency vibrations; and 4) the putative long-range coherent electron transfer between metallointercalators in DNA. Theoretical studies are also proposed of current quantum theoretical models for electron transfer and vibrational relaxation. Since many commercially important chemical reactions take place in polar solvents such as water, it is important to understand the influence which such solvents have on the reaction dynamics. A number of effects, such as solvent cage effects, vibrational relaxation and quantum mechanical tunneling, which are not present in the gas phase completely dominate condensed phase chemical reactions. It is important to develop reliable theories for model chemical systems which can then be applied to improving the efficiency of commercially important chemical reactions. The work which is being performed by Barbara provides an important experimental basis for the development of such theories.