Studies of the Control of Quantum Dynamics

Stuart Rice获得了理论与计算化学项目的资助，继续研究量子多体系统进化的控制理论，并将其应用于化学反应产物的选择性增强。将进行四个方面的研究：1)改进和扩展Kobrak-Rice光选择绝热通道方案；2)激发态分子的简化动力学描述的准确性；3)控制嵌入在溶剂中的分子的演化；4)可能存在量子动力学控制范围的基本限制。相干控制的许多理论方法将作为控制反应中产物选择性的广义受激拉曼绝热通道（StiRAP）过程的扩展而发展。在化学的整个进化过程中，对反应产物形成的选择性控制一直是人们所追求的目标。迄今为止，这种控制只能在宏观层面上完成，通过操纵外部因素，如温度、压力、溶剂性质等。随着可调谐激光的出现，人们希望在微观水平上控制产物的选择性，并且可以选择性地破坏分子内的单个键。人们很快发现，被分子吸收的能量不容易局限在单个键上，而是倾向于在整个分子中重新分布。然而，最近，激光选择化学的概念有了重生，由赖斯和其他人发展的理论表明，能量可以通过仔细选择规定形状的复杂激光脉冲序列来定位。如果能将这一理论应用于实验，仍有可能实现化学反应微观选择性控制的目标。

Stuart Rice is supported by a grant from the Theoretical and Computational Chemistry Program to continue his work on the theory of control of the evolution of quantum many body systems with applications to the selective enhancement of products of a chemical reaction. Four areas of study will be pursued: 1) refinements and extensions of the Kobrak-Rice photoselective adiabatic passage scheme; 2) the accuracy of reduced dynamical descriptions of an excited molecule; 3) the control of the evolution of a molecule embedded in a solvent; and 4) the possible existence of a fundamental limit to the extent of control of quantum dynamics that is attainable. Much of the theoretical approach to coherent control will be developed as an extension to the generalized Stimulated Raman Adiabatic Passage (StiRAP) process for control of product selectivity in a reaction.The achievement of selective control of product formation in a reaction has been sought persistently throughout the evolution of chemistry. To date, such control has only been accomplished at the macroscopic level, by the manipulation of external factors such as temperature, pressure, solvent character, etc. With the advent of the tunable laser, it was hoped that product selectivity could be controlled at the microscopic level, and that individual bonds within a molecule could be selectively broken. It was very quickly found that energy absorbed by a molecule was not easily localized in individual bonds, but preferred to redistribute throughout the molecule. More recently, however, the concept of laser selective chemistry has had a rebirth, and theories developed by Rice and others have shown that energy could be localized by carefully choosing a complex sequence of laser pulses of prescribed shapes. If this theory can be put to practice experimentally, it may still be possible to realize the goal of microscopic selective control of chemical reactions.