Analyzing the results, it is likely that photolysis of IO - 3 to yield loss of oxygen is too slow to significantly alter NPF mechanisms at any plausible UV solar irradiance. For clusters, we see photolysis by O loss to increase at least linearly with addition of I 2 O 5 , and on a high-UV day, O loss from (I 2 O 5 ) 3 (IO - 3 ) and larger clusters could be expected to occur in a matter of minutes. In all cases, photolysis yielding I 2 O 5 is roughly an order of magnitude faster than loss of O. This process would simply compete with uptake of I 2 O 5 , while loss of O atoms will qualitatively change the chemistry of the nascent particle. These rates are of similar orders of magnitude to those presented for smaller iodine oxides, 66 suggesting that photochemistry in more complex mixed new particles is likely to continue to be relevant.