Phys.org April 19, 2024
The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store and release a substantial amount of chemical energy. Prior work observed signatures of ultrafast molecular dynamics in both isomers upon ultraviolet excitation but could not follow the electronic relaxation all the way back to the ground state experimentally. An international team of researchers (USA – Kansas State University, University of Nebraska–Lincoln, SLAC National Accelerator Laboratory, Brown University, UK, Germany, Italy, Sweden, Australia) identified two competing pathways by which electronically excited quadricyclane molecules relaxed to the electronic ground state. The fast pathway (<100 femtoseconds) was distinguished by effective coupling to valence electronic states, while the slow pathway involved initial motions across Rydberg states and took several hundred femtoseconds. Both pathways facilitated interconversion between the two isomers. They predicted that the branching ratio of norbornadiene/quadricyclane products immediately after returning to the electronic ground state to be approximately 3:2… read more. Open Access TECHNICAL ARTICLE
Schematic of the QC ⇄ NBD interconversion. Credit: Nature Chemistry volume 16, pages499–505 (2024)Â