The reaction of OH with NO₂ and the deactivation of O(¹D) by CO

NO 2 was photolyzed with 2288 Å radiation at 300° and 423°K in the presence of H 2 O, CO, and in some cases excess He. The photolysis produces O( 1 D ) atoms which react with H 2 O to give HO radicals or are deactivated by CO to O( 3 P ) atoms The ratio k 5 / k 3 is temperature dependent, being 0.33 at 300°K and 0.60 at 423°K. From these two points, the Arrhenius expression is estimated to be k 5 / k 3 = 2.6 exp(−1200/ RT ) where R is in cal/mole – °K. The OH radical is either removed by NO 2 or reacts with CO The ratio k 2 / k α is 0.019 at 300°K and 0.027 at 423°K, and the ratio k 2 / k 0 is 1.65 × 10 −5 M at 300°K and 2.84 × 10 −5 M at 423°K, with H 2 O as the chaperone gas, where k α = k 1 in the high‐pressure limit and k 0 [M] = k 1 in the low‐pressure limit. When combined with the value of k 2 = 4.2 × 10 8 exp(−1100/ RT ) M −1 sec −1 , k α = 6.3 × 10 9 exp (−340/ RT ) M −1 sec −1 and k 0 = 4.0 × 10 12 M −2 sec −1 , independent of temperature for H 2 O as the chaperone gas. He is about 1/8 as efficient as H 2 O.