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Mode-Specific versus Local Heating Effects in Infrared-Laser-Driven Reactions
Sindhana Pannir-Sivajothi1,2, Yong Rui Poh1, Zi-Jie Liu3
1Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92037, United States.
The Journal of Physical Chemistry. A
|January 26, 2026
Summary
Controlling molecular reactivity with infrared lasers is challenging due to rapid energy redistribution. This study quantifies how laser-induced heating and vibrational assistance enhance reaction rates, with low-frequency modes showing substantial gains.
Area of Science:
- Chemical Physics
- Molecular Dynamics
- Laser Chemistry
Background:
- Controlling molecular reactivity using infrared lasers targets specific vibrational modes.
- Rapid intramolecular vibrational energy redistribution (IVR) limits precise energy control.
- Advances in femtosecond laser technology enable revisiting laser-driven reactivity.
Purpose of the Study:
- To theoretically quantify mode-specific assistance and laser-induced heating contributions to reaction rate enhancements.
- To investigate the influence of activation barriers on rate enhancements.
- To determine the impact of laser driving conditions on reaction rates.
Main Methods:
- Theoretical modeling of laser-driven molecular reactions.
- Quantification of energy transfer pathways (IVR).
- Analysis of reaction rate enhancements under varying conditions (pulsed vs. continuous-wave lasers, low- vs. high-barrier reactions).
Main Results:
- Reactions with lower activation barriers show smaller relative rate enhancements.
- Local heating dominates rate enhancement for low-barrier reactions; vibrational assistance is more prominent for high-barrier reactions.
- Pulsed laser driving offers significantly greater rate enhancements than continuous-wave driving for equivalent absorbed power.
- Substantial rate enhancements are achievable for low-frequency modes.
Conclusions:
- Laser-induced heating and vibrational assistance both contribute to reaction rate enhancements.
- The relative importance of these mechanisms depends on the reaction's activation barrier and solvent properties.
- While overall rate enhancements are modest, specific conditions, particularly involving low-frequency modes, can yield significant increases.
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