RUI: Strong-Field Control of Intramolecular Dynamics in Polyatomic Molecules

Augustana University Association, Sioux Falls SD

Investigators

Abstract

Atoms can absorb energy from light, a process that excites their electrons. When molecules, which are composed of multiple atoms, absorb light in a similar manner, the absorbed energy can quickly be transferred away from the electrons and cause the atoms within the molecule to move. The molecules can vibrate by stretching or bending, or the atoms in the molecule can rotate about each other. This sort of behavior is a key step in processes such as vision or photosynthesis, and understanding how this energy transfer is accomplished can help design more efficient collection of light or to construct light-activated molecular switches. At an extreme level, intense, ultrashort laser pulses can manipulate transient molecular structure directly. Stated another way, the precise application of a laser pulse can be thought of as a light-based reagent that alters a chemical process in a desired manner. For these reasons, this basic research explores how the excitation of electrons in molecules by light leads to changes in transient molecular structure and seeks ways of controlling those processes. These studies are done with undergraduate students, which provides motivation for further scientific education and therefore helps develop a highly skilled workforce. This research uses momentum imaging schemes to measure the structural evolution of molecules following the application of intense, ultrafast laser pulses. Photoelectron circular dichroism is a sensitive probe of chiral structure in molecules and one part of this research aims to use these signals to probe laser-induced transitions from achiral to chiral structures. Coincidence ion momentum imaging can identify specific dynamic processes in molecules, and multi-particle cumulant analysis can increase the data acquisition rate by orders of magnitude over traditional coincidence analysis. Developing this detection approach is the second main goal of this research. Both detection schemes can then be linked to ultrafast laser pulse shaping and used to explore coherent control of molecular dynamics, either through open- or closed-loop control schemes. These studies explore fundamental questions about electronic to nuclear coupling in molecules and how these processes might be controlled. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.