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Dynamical outcomes of quenching: reflections on a conical intersection
Julia H Lehman1, Marsha I Lester
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323;
Annual Review of Physical Chemistry
|April 3, 2014
Summary
Collisional quenching of excited OH radicals is explored through experiments and theory. Conical intersections explain how these reactions occur, matching theoretical predictions for the OH-H2 system.
Area of Science:
- Chemical Physics
- Molecular Dynamics
- Spectroscopy
Background:
- Collisional quenching of electronically excited radicals is crucial for understanding chemical reactions.
- The hydroxyl radical (OH) in its A(2)Σ(+) excited state is a key species in atmospheric and combustion chemistry.
- Nonadiabatic effects, particularly conical intersections, play a significant role in the dynamics of quenching processes.
Purpose of the Study:
- To review experimental studies on the dynamical outcomes of OH A(2)Σ(+) radical quenching by molecular partners.
- To connect experimental observations with theoretical insights into the role of conical intersections.
- To validate theoretical models using benchmark systems like OH-H2.
Main Methods:
- Experimental measurements of branching ratios, kinetic energy release, and product quantum state distributions.
- Theoretical investigations employing dynamical calculations.
- Analysis of nonadiabatic coupling regions and conical intersections.
Main Results:
- Experimental data reveal detailed dynamical information about reactive and nonreactive decay channels.
- Theoretical studies identify conical intersections as key facilitators of the quenching process.
- Dynamical calculations for OH-H2 show good agreement with experimental results, confirming the importance of conical intersections.
Conclusions:
- The dynamical outcomes of OH A(2)Σ(+) quenching are strongly influenced by the system's evolution through conical intersections.
- Experimental and theoretical approaches provide complementary insights into radical-molecule collisions.
- The OH-H2 system serves as a valuable benchmark for understanding quenching dynamics governed by nonadiabatic effects.
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