Excited State Dynamics Of Molecular Switches

Currently working on this project: Cassie Ward, Amanda Houk, and Tim Quincy

Techniques: Pump-Probe, Pump-Repump-Probe, 2PA

The first project looks at excited state dynamics of color-changing photoswitches. These molecules reversibly convert between two isomers with very different absorption spectra and are prime candidates for use in high-density data storage devices, such as 3-dimensional, many-layer DVDs. Our experiments follow the transformation from one isomer to another after the system absorbs a photon. Those ring-opening and ring-closing reactions involve up to three electronic states.

A key question that physical chemists want to answer is exactly how a system transfers from one electronic state to another, a process called non-adiabatic transition. Non-adiabatic transitions generally occur through conical intersections, where the potential energy surfaces cross. Conical intersections are a hot topic these days because they are ubiquitous in excited state reactions. We use new excitation schemes, such as simultaneous and sequential two-photon excitation, to explore the reaction mechanisms of photo-switching and then apply what we learn to steer the reaction and thus improve conversion yields for ring-opening and closing.

Working with collaborators in the Femtoscopy Lab at the University of Rome, we can probe changes in the vibrational structure on the excited-state surface using Femtosecond Stimulated Raman Spectroscopy (FSRS). This new technique allows us to learn about the vibrational structure of the photoswitch as it undergoes the cyclization reaction.


Elles Group Highlights
Funding Sources