Related Experiment Video
Updated: Jun 9, 2026
07:03
Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors
Published on: November 15, 2016
Conical Intersection Induced Valley-Ridge Inflection Drives Chemiluminescence in the SO2 Afterglow Reaction
Anjana Vijayan1, Mahesh Gudem1
1Department of Chemistry, Indian Institute of Technology Dharwad, Dharwad, Karnataka 580011, India.
The Journal of Physical Chemistry Letters
|June 8, 2026
Summary
This study reveals a novel chemiluminescence mechanism in the SO2 afterglow reaction, distinct from peroxide-based systems. A conical intersection-induced valley-ridge inflection directs the reaction to produce SO2 in different electronic states.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Computational Chemistry
Background:
- Chemiluminescence mechanisms are primarily understood through cyclic peroxide studies.
- A general mechanistic framework for chemiluminescence is lacking.
- The SO2 afterglow (SO + O) reaction produces SO2 in ground and excited electronic states.
Purpose of the Study:
- To investigate the chemiluminescence mechanism in the SO2 afterglow reaction.
- To elucidate the role of conical intersections and nonadiabatic effects.
- To establish a general mechanistic framework for chemiluminescence.
Main Methods:
- X-ray Multi-Configuration Self-Consistent Field with Second-Order Perturbation Theory (XMS-CASPT2) calculations.
- Nonadiabatic dynamics calculations.
- Analysis of conical intersection (CI) and valley-ridge inflection (VRI) topologies.
Main Results:
- A conical intersection-induced valley-ridge inflection (CI-VRI) was identified on the T1 surface.
- This CI-VRI pathway branches to produce SO2 in distinct electronic states, unlike conventional VRIs.
- Nonadiabatic effects significantly impact reaction dynamics around the CI-VRI, differing from previous observations in air afterglow.
Conclusions:
- The identified CI-VRI mechanism is fundamentally different from peroxide-based chemiluminescence.
- This mechanism may represent a common motif in gas-phase chemiluminescence.
- Understanding such mechanisms is crucial for developing general chemiluminescence theories.
Related Concept Videos
01:14Photoluminescence: Applications
Photoluminescence offers a wide range of applications due to its inherent sensitivity and selectivity. This technique allows for both direct and indirect analyses of the analyte. Direct quantitative analysis is possible when the analyte exhibits a favorable quantum yield for fluorescence or phosphorescence. However, an indirect analysis may be feasible if the analyte is not fluorescent or phosphorescent, or if the quantum yield is unfavorable. Indirect methods include reacting the analyte with...
01:23Photoluminescence: Fluorescence and Phosphorescence
Photoluminescence is a process where a molecule absorbs light energy and re-emits it in the form of light. This phenomenon occurs when a substance absorbs photons, promoting its electrons to higher energy level excited states, followed by a relaxation process in which the electrons return to their original ground state energy levels and emit light. Photoluminescence is widely observed in various materials, including semiconductors, and organic and inorganic compounds.
A pair of electrons in a...
A pair of electrons in a...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:26Variables Affecting Phosphorescence and Fluorescence
Fluorescence and phosphorescence are essential phenomena in fields like analytical chemistry, biological imaging, and materials science, where they detect molecular properties and visualize cellular structures. Understanding the variables that influence these luminescent behaviors is crucial for maximizing accuracy and efficiency in their applications. These variables can broadly be grouped into chemical structure, solvent properties, and external conditions, each playing a distinct role in...
01:27Inductive Effects on Chemical Shift: Overview
The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
01:05Total Internal Reflection Fluorescence Microscopy
Total internal reflection fluorescence microscopy or TIRF is an advanced microscopic technique used to visualize fluorophores in samples close to a solid surface with a higher refractive index, such as a glass coverslip. TIRF only allows fluorophores in proximity to the solid surface to be excited. When light from a medium with a lower refractive index (such as air) hits the glass coverslip at a critical angle, the light undergoes total internal reflection stead of passing through the glass.