Adventures in ozoneland: down the rabbit-hole

Area of Science:

• Atmospheric Chemistry
• Chemical Kinetics
• Spectroscopy

Background:

• The Stabilized Criegee Intermediate (SCI) plays a crucial role in atmospheric oxidation processes.
• Understanding the reaction pathways and intermediates in alkene-ozone systems is vital for atmospheric modeling.
• Previous studies have focused on identifying and characterizing transient species in these reactions.

Purpose of the Study:

• To investigate the pressure dependence of product yields in alkene + ozone systems.
• To elucidate the reaction mechanism involving primary ozonides, SCI, and vinyl hydroperoxide (VHP).
• To gain fundamental insights into collisional energy transfer in chemically activated systems.

Main Methods:

• Conducting complementary experiments to measure product yields (e.g., OH radicals, ozonides) at varying pressures.
• Analyzing reaction sequences involving different alkene carbon numbers and system pressures.
• Utilizing spectroscopic techniques to identify and characterize reaction intermediates.

Main Results:

• Observed a succession of weakly bound intermediates: primary ozonide, SCI, and VHP.
• Identified VHP as a significant bottleneck in the reaction coordinate.
• Narrowed the experimental conditions for direct SCI observation based on alkene carbon number and pressure.

Conclusions:

• The study provides strong evidence for VHP as a rate-limiting step.
• Findings advance the fundamental understanding of energy transfer in complex chemical systems.
• Results directly inform atmospheric chemistry, including HO(x) radical formation and secondary organic aerosol production.