Revisiting atmospheric sulfur chemistry: Acid-catalyzed pathways do not control H(2)SO(4) formation.

Acid-catalyzed SO3 hydration kinetics is controlled by a preceding loose transition state forming the precursor complex, and revised kinetics yields no significant impact on simulated atmospheric H2SO4 concentrations.

• Why it matters: Limited kinetics data has left sulfuric acid formation pathways poorly resolved, affecting understanding of new particle formation and radiatively important aerosol processes.
• What they did: Coupled-cluster calculations and reaction rate theory quantified acid-catalyzed SO3 hydration, then the revised kinetics were incorporated into the GEOS-Chem global chemistry transport model.
• The result: The study reverses the view that acid catalysis dominates SO3 hydration, instead supporting that water catalysis dominates, and shows no significant impact of acid-catalyzed SO3 hydration on simulated H2SO4.