Active Control of Chemical Reactions

University Of Chicago, Chicago IL

Investigators

Abstract

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.