When Mechanism II for ozone destruction operates with X = Cl and X’ = Br, the radicals ClO and BrO react together to reform atomic chlorine and bromine. A fraction of the latter process proceeds by the intermediate formation of BrCl, which does not decompose and restart the mechanism until dawn.
Deduce why all the bromine exists as BrCl at night, even though only a fraction of the ClO with BrO collisions yields this product.