Active Control of Chemical Reactions

在这项由化学部理论和计算化学计划资助的奖项中，赖斯将研究量子多体系统演化的主动控制理论，以建立在密液相中实现单分子反应的主动控制的条件。这些研究的主要焦点将是开发新的方法变体，这些方法使用相干激发态，无论是否有绝热布居转移。主要集中在开发新的受激拉曼绝热通道(STIRAP)激光激发方案，用于气相和溶相反应。还将研究其他有希望的方法，以及对以前的分子动力学主动控制实现的改进和扩展。在整个化学发展过程中，一直在寻求对化学反应中产物形成的选择性控制。使用这种对反应的控制将允许人们大部分或完全地产生特定的产品。通过控制外部因素，如温度、压力、溶剂性质等，在宏观水平上实现了控制。随着可调谐激光的出现，人们希望可以在微观水平上控制产物的选择性，并选择性地破坏分子中的各个键。人们很快发现，被分子吸收的能量不容易集中在单个键中，而是倾向于在整个分子中重新分配。然而，最近，激光选择化学的概念得到了重生，赖斯和其他人发展的理论表明，通过仔细选择指定形状的复杂激光脉冲序列，可以实现能量局部化。如果这一理论能够在实验上付诸实践，就有可能实现化学反应微观选择性控制的目标。

In this award funded by the Theoretical and Computational Chemistry Program of the Chemistry Division, Rice will study the theory for the active control of the evolution of quantum many-body systems in order to establish conditions under which active control of a unimolecular reaction can be achieved in a dense liquid phase. The principal focus in these investigations will be on developing new variants of methods that use coherent excitation of states with or without adiabatic transfer of population. A main focus in on the development of new stimulated Raman adiabatic passage (STIRAP) laser excitation schemes for both gas phase and solution phase reactions. Other promising methods as well as refinements and extensions of previous implementations of active control of molecular dynamics will also be studied.Selective control of product formation in a chemical reaction has been sought persistently throughout the evolution of chemistry. Using such control of a reaction would allow one to generate a particular product mostly or completely. Control has been accomplished at the macroscopic level by manipulating 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 will be possible to realize the goal of microscopic selective control of chemical reactions.