Correlating Electronic and Atomic Motions in Photoinduced Electron-Proton Transfer Reactions with Two-Dimensional Electronic-Vibrational and X-ray Spectroscopies

University Of Washington, Seattle WA

Investigators

Abstract

In this project funded by the Chemical Structure and Dynamics-A program of the Chemistry Division, Professor Munira Khalil of the University of Washington is developing a microscopic description of how a hydrogen atoms move from a donor to an acceptor following the absorption of light. To meet this experimental challenge, new spectroscopic methods capable of directly measuring the coupling of electronic and atomic motions are developed spanning the electromagnetic spectrum from the infrared (IR) to X-rays. An outreach program developed by Professor Khalil includes a hands-on optics module for middle school girls from STEM-disadvantaged backgrounds in a unique "Girls on Science" program run through the University of Washington's Burke Museum. The broader impacts of this work include training the next generation of scientists in state-of-the-art ultrafast techniques in the laboratory and at synchrotrons and free electron laser sources, creating new femtosecond technologies, and an increased understanding of the photo-induced electron-proton transfer process. This research has two main objectives with a two-pronged experimental approach. The first is to develop the use of novel two-dimensional femtosecond electronic and infrared spectroscopy (2D EV) using a train of two ultraviolet (UV) pulses followed by a broadband mid IR pulse. This will enable the group to directly measure the coupled electronic charge density and the movement of the hydrogen atom in photo-induced coupled electron-proton transfer in model intra and inter-molecular hydrogen bonded complexes. The second thrust is using ultrafast X-ray absorption and Resonant Inelastic X-ray scattering (RIXS) spectroscopy to directly monitor the charge distribution around the hydrogen bond donor and acceptor atoms. The equilibrium X-ray experiments are being conducted at the Advanced Light Source (ALS) and the ultrafast RIXS experiments are conducted at the Linac Coherent Light Source (LCLS). Photo-induced electron-proton transfer is a central reaction in several natural and artificial energy conversion processes. Possible future impacts include the development of new molecules, materials and devices for alternative energy production.