The gas-phase reaction between O3 and HO radical: a theoretical study

Area of Science:

• Atmospheric Chemistry
• Quantum Chemistry
• Chemical Kinetics

Background:

• The reaction between ozone and hydroxyl radicals is a key process in atmospheric chemistry.
• This reaction plays a significant role in stratospheric ozone destruction.
• Understanding this reaction mechanism is vital for accurate atmospheric modeling.

Purpose of the Study:

• To theoretically investigate the reaction mechanism between ozone and hydroxyl radical.
• To compute the energy profile and reaction barriers for the formation of HO4.
• To predict the rate constant for the reaction using theoretical methods.

Main Methods:

• Theoretical study employing quantum chemical calculations.
• Identification of pre-reactive complex (C1) and transition states (TS1, TS2).
• Application of Variational Transition State Theory (VTST) for kinetic analysis.

Main Results:

• The reaction was computed to be exothermic (42.72 kcal mol(-1)).
• Low energy barriers for TS1 (1.80 kcal mol(-1)) and TS2 (2.26 kcal mol(-1)) at 0 K were determined.
• Predicted rate constant at 298 K (7.37 x 10(-14) cm3 molecule(-1) s(-1)) closely matches experimental values.

Conclusions:

• The theoretical model accurately describes the ozone-hydroxyl radical reaction pathway.
• Calculated energetics and kinetics align well with experimental data.
• This work provides valuable insights into stratospheric ozone depletion mechanisms.