Special Seminars
Speaker: Joshua S. Kretchmer, Asst. Prof., Georgia Institute of Technology
Date: Tuesday, April 28, 2026 at 4-5 pm
Location: Noyes Lab 147
Faculty host: Garnet Chan
Title: Real-time simulations of ultrafast electron relaxation dynamics
Abstract: The Kretchmer Group develops simulation methods at the intersection of electronic structure theory and quantum dynamics. We apply our methods to examine electron and spin dynamics, non-adiabatic processes, and charge transport in complex molecular and material systems including weakly-bound molecular clusters, chiral and helical molecules, and perovskites. In this talk, I will highlight our recent development of a new methodology to unravel the competing electronic relaxation pathways following inner-shell ionization in weakly bound systems. When an inner-shell electron is removed, another electron relaxes to fill the vacancy, which can transfer energy to a nearby entity, generating a low-energy secondary ionized electron. Critically, the location of the electron that relaxes and the secondary ionized electron can originate from either the original molecule or a neighboring molecule. The relaxation can also compete with electron, hole, and even proton transfer. Our work combines real-time DFT with a complex absorbing potential to simulate the explicit dynamics of this complex array of processes. We have additionally introduced coupled electron-nuclear dynamics through Ehrenfest dynamics, which enabled an in-depth investigation of the fragmentation pathways in the water dimer following inner-valence ionization. Our simulations identified a previously unknown relaxation channel essential to reproducing the experimentally observed fragmentation products of our collaborators, prompting a reinterpretation of the origin of low-energy electrons in hydrogen-bonded systems such as water.
These events are open to the Caltech/JPL community members only. No recordings are allowed except by permission of the organizer.