Fig. 1: Coincident formation of HIO3 and HOI in the early stages of iodine oxidation.
From: The gas-phase formation mechanism of iodic acid as an atmospheric aerosol source
a–g, Time-resolved measurements of key iodine species (a,b,d show precursors to HIO3 (f) and HOI (g), and c and e show higher-oxide routes) are compared with model predictions after the start of I2 photolysis at green wavelengths within the CERN CLOUD chamber. Measured concentrations (grey lines) of HIO3 and HOI exceed 107 molecules per cm3 (molec cm−3) within minutes. Established gas-phase iodine chemistry (model base case, dashed blue lines) forms neither HIO3 nor HOI, contrary to the observations, and overestimates the concentrations of IOIO and I2O4. The extended model (solid red line), including reactions (R1) and (R2) and considering a longer thermal lifetime of IOIO, achieves good mass and temporal closure for HIO3, HOI, IOIO and I2O4.
