Probing Hydrogen-Bond Dynamics in 1-Propanol Following Multiphoton Ionization via Liquid-Phase Ultrafast Electron Diffraction
ORAL
Abstract
Full Author List: H. Wu, T. Yoon, D. Mishra, L. Hoffmann, S. Bhattacharyya, M. Centurion, X. Cheng, D. P. DePonte, S. W. Eisenberg, R. J. England, M. Grassl, C. Y. Hampton, L. F. Heald, J. Heo, M. Ihme, R. Jarupula, F. Ji, B. Kaufman, D. Kim, M. Kling, J. D. Koralek, P. Kramer, R. A. Lemons, M. Li, M.-F. Lin, M. Mo, K. Murari, J. P. F. Nunes, S. Sahel-Schackis, S. P. Weathersby, T. Xu, C. Yang, O. Gessner, A. Reid, Y. Mao, Y. Liu , H. Yong
Understanding how solvent molecules respond to intense optical fields is critical for studying ultrafast chemical reactions in solution. In multiphoton-induced photochemical reactions, where high pulse fluence is typically required, solvent ionization becomes inevitable. This process can generate solvated electrons and reactive radical species that may influence or even alter the primary photochemical dynamics of solutes. Solvent ionization also introduces additional complexity in data analysis, making it challenging to disentangle genuine solute dynamics from solvent-ionization-induced effects. Characterizing the intrinsic ultrafast ionization response of solvent molecules is therefore crucial for separating these contributions. Here, we report a liquid-phase ultrafast electron diffraction experiment using a liquid jet of pure 1-propanol subjected to 266 nm multiphoton ionization (MPI) at a modest laser peak intensity of ~1013 W/cm2, resulting in an estimated ionization fraction of ~40%. This enables direct observation of transient structural changes with femtosecond time resolution. Unlike previous strong-field ionization studies of gas-phase 1-propanol, which were dominated by tunneling ionization and exhibited multiple dissociation channels [1], no evidence of fragmentation is observed in the liquid phase under MPI. Instead, experimental and theoretical results suggest that proton transfer dynamics occurs between ionized and neutral propanol molecules in the liquid environment within a few hundred femtoseconds after ionization, accompanied by a coherent structural oscillation with a period of ~400 fs. This study provides new insights into molecular ionization dynamics in a liquid environment and will be valuable for future ultrafast studies in solution.
[1] D. Mishra et al., Phys. Chem. Chem. Phys. 2022, 24, 433–443.
Understanding how solvent molecules respond to intense optical fields is critical for studying ultrafast chemical reactions in solution. In multiphoton-induced photochemical reactions, where high pulse fluence is typically required, solvent ionization becomes inevitable. This process can generate solvated electrons and reactive radical species that may influence or even alter the primary photochemical dynamics of solutes. Solvent ionization also introduces additional complexity in data analysis, making it challenging to disentangle genuine solute dynamics from solvent-ionization-induced effects. Characterizing the intrinsic ultrafast ionization response of solvent molecules is therefore crucial for separating these contributions. Here, we report a liquid-phase ultrafast electron diffraction experiment using a liquid jet of pure 1-propanol subjected to 266 nm multiphoton ionization (MPI) at a modest laser peak intensity of ~1013 W/cm2, resulting in an estimated ionization fraction of ~40%. This enables direct observation of transient structural changes with femtosecond time resolution. Unlike previous strong-field ionization studies of gas-phase 1-propanol, which were dominated by tunneling ionization and exhibited multiple dissociation channels [1], no evidence of fragmentation is observed in the liquid phase under MPI. Instead, experimental and theoretical results suggest that proton transfer dynamics occurs between ionized and neutral propanol molecules in the liquid environment within a few hundred femtoseconds after ionization, accompanied by a coherent structural oscillation with a period of ~400 fs. This study provides new insights into molecular ionization dynamics in a liquid environment and will be valuable for future ultrafast studies in solution.
[1] D. Mishra et al., Phys. Chem. Chem. Phys. 2022, 24, 433–443.
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Presenters
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Haowei Wu
- University of California San Diego