Tracking coherent vibronic and vibrational motions in ultrafast proton transfer

Decades of theoretical and experimental work on excited-state
intramolecular proton transfer systems indicate that
electronic-vibrational (vibronic) coupling plays a significant role in
ultrafast proton transfer reactions. However, the participating atomic
motions of this chemical reaction have yet to be directly observed. The
challenge in observing these rapid proton transfer processes lies in
simultaneously probing both the electronic and vibrational degrees of
freedom. Addressing these challenges requires advanced spectroscopic
techniques that provide multidimensional (electronic and vibrational)
structural information with femtosecond time resolution. Here, we use
multidimensional electronic-vibrational spectroscopy to directly observe
the vibronic motions driving the non-adiabatic excited-state proton
transfer process in 10-hydroxybenzo[h]quinoline. We measure the interplay
between high and low-frequency vibrations, mapping the proton transfer
trajectory on two vibronically coupled electronic states. Our study
enables the observation of vibronic coherence transfer, structural
rearrangements, and intramolecular vibrational redistribution during and
following proton transfer. Here we provide the source data and
supplementary data for the figures in the main text and Supplementary
Information.