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High-Resolution Time-Resolved PEPICO with Tunable Vacuum Ultraviolet Photoionization
Daniel Rösch1, Kyung Chul Woo2, Jared A Echternach2
1Department of Physics, Technical University Dortmund, 44227 Dortmund, Germany.
The Journal of Physical Chemistry. A
|February 20, 2026
Summary
We enhanced a double-imaging photoelectron photoion coincidence (i^2PEPICO) spectrometer with tunable ionization. This improved time resolution to 7 μs, enabling detailed chemical reaction studies and revealing unexpected photodissociation products.
Area of Science:
- Chemical Physics
- Spectroscopy
- Reaction Dynamics
Background:
- The double-imaging photoelectron photoion coincidence (i^2PEPICO) technique is crucial for studying chemical reactions.
- Previous instruments faced limitations in time resolution and background noise.
Purpose of the Study:
- To enhance the i^2PEPICO spectrometer with tunable ionizing radiation.
- To improve time resolution and address challenges in photoelectron spectroscopy.
Main Methods:
- Coupling the i^2PEPICO spectrometer with tunable vacuum ultraviolet radiation.
- Utilizing cation imaging for signal restriction and velocity map imaging for temporal blurring reduction.
- Quantifying instrument response function and addressing background electron noise.
Main Results:
- Demonstrated viscous flow in gas expansion dynamics prior to ionization.
- Achieved a time resolution upper bound of 7 μs, a significant improvement.
- Identified unexpected products in methanol photodissociation, highlighting the utility of universal imaging.
Conclusions:
- The enhanced i^2PEPICO spectrometer offers superior time resolution and capabilities for chemical reaction studies.
- Velocity map imaging effectively mitigates temporal blurring in ex situ sampling.
- The instrument's advancements facilitate quantitative analysis and discovery of novel reaction pathways.
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