Collinear UV-mid-IR cross-validation updates HO(2) self-reaction kinetics and implications for tropospheric HO(x) and H(2)O(2).

Updated HO(2) self-reaction kinetics are approximately 50% faster under humid conditions and up to twice as fast in the upper troposphere, impacting atmospheric models.

• Why it matters: Accurate understanding of HO(2) reactions is crucial because they influence the formation of hydrogen peroxide and radical chemistry, affecting air quality and climate models.
• What they did: Using collinear photolysis-probe spectroscopy with UV and mid-IR absorption, the study measured HO(2) reaction rates across relevant atmospheric conditions, revealing higher rate coefficients than current standards.
• The result: Incorporating these revised kinetics into models reduces near-surface HO(2) by up to 12% and increases H(2)O(2) by up to 28%, with significant implications for understanding tropospheric radical chemistry.