Laser induced fluorescence (LIF) from the (0, 0), (2, 0), (3, 0), and (2, 1) bands of the A 2 3 ← X 2 3 system of IO was detected. Using LIF detection of IO, the rate coefficients for I + O 3 → IO + O 2 (k 1 ) and IO + NO → I + NO 2 (k 2 ) reactions were measured between 240 and 370 K to be k 1 (T) = (2.3 ± 0.7) 10 - 1 1 exp[--(860 ± 100)/T] and k 2 (T) = (1.02 ± 0.31) 10 - 1 1 exp[(185 ± 70)/T] cm 3 molecule - 1 s - 1 .