Theory of Dynamical Correlated-Electron Processes in Molecules Induced and Probed with x-Ray Light

Louisiana State University, Baton Rouge LA

Investigators

Abstract

X-ray free-electron laser (XFEL) light sources are opening avenues to observe the motion of electrons inside matter with unprecedented space and time resolution. By accessing core levels, x-ray pulses can discriminatively interrogate different atoms in molecules, and they can do so with femtosecond (one millionth of a billionth of a second) resolution or faster, reaching the natural scales at which electrons move in these systems. This project will study a range of time-dependent correlated-electron processes in organic molecules that can be induced and probed with x-rays. To do so, the PI and his group will leverage existing quantum-chemistry packages to simulate the interaction between x-rays and molecules. While theoretical, this project will aim to identify processes and observables that are accessible to measurements, with the ultimate objective to collaborate with XFEL experimental campaigns. The project will serve the national interest through the advancement of x-ray-enabled molecular science and through the development of human resources via the training of junior researchers at the undergraduate and graduate levels. The PI and his group will study the interactions between molecules and x-ray light, as the vehicle for triggering and observing time-dependent correlated processes in these systems, with an emphasis on core electrons. Of the two main objectives, one will be to routinely simulate a range of correlated processes in organic molecules that can be induced and/or probed with x-rays. To do so, simulations will use an explicit treatment of electron correlation in a multi-reference complete- or restricted-active space formal-ism (MR-CAS/RAS) using density-functional-theory, or otherwise optimized, molecular orbitals to improve the convergence of the MR-CAS/RAS. An additional objective of the project will be to uniquely connect the correlated dynamics and processes observed in these simulations, i.e., the wave functions, to observables that are accessible to experiments. This project will also investigate some of the practical aspects of modeling light-matter interactions with realistic XFEL pulses. This project is jointly funded by the Atomic, Molecular, and Optical Physics Theory Program and the Established Program to Stimulate Competitive Research (EPSCoR). 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.