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Dimol Emission of Oxygen Made Possible by Repulsive Interaction
Attila Tajti1, György Lendvay2, Péter G Szalay1
1ELTE Eötvös Loránd University, Laboratory of Theoretical Chemistry, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary.
The Journal of Physical Chemistry Letters
|July 6, 2017
Summary
Collision-induced emission explains the red light from singlet molecular oxygen. This process occurs "on-the-fly" during molecular collisions, accessing repulsive interactions that enhance light emission.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Quantum Mechanics
Background:
- Chemiluminescence involves light emission from chemical reactions.
- Singlet molecular oxygen (O2(a1Δg)) produces a characteristic red light.
- Previous theories suggested weak van der Waals interactions for O2(a1Δg) dimers.
Purpose of the Study:
- To investigate the mechanism of red light emission from singlet molecular oxygen.
- To explain the discrepancy between theoretical predictions and experimental observations of O2(a1Δg) emission.
- To determine the role of intermolecular interactions in collision-induced emission.
Main Methods:
- High-level ab initio calculations of the O2(a1Δg)-O2(a1Δg) potential energy surface and oscillator strength.
- Development of a semiclassical model to evaluate the contribution of molecular orientations.
- Comparison of theoretical predictions with experimental data for emission peak position and rate coefficients.
Main Results:
- Oscillator strength increases significantly at short intermolecular separations on the repulsive part of the potential energy surface.
- Collision-induced emission, occurring "on-the-fly", is proposed as the primary mechanism.
- The model accurately predicts the emission peak position and reasonably estimates the rate coefficient.
Conclusions:
- The peculiar red light emission from singlet molecular oxygen is attributed to collision-induced processes.
- Short-range repulsive interactions during collisions are crucial for enhancing oscillator strength.
- This study provides a theoretical framework consistent with experimental observations of O2 chemiluminescence.
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