Kinetic measurements on the system: 2NO 2 = N 2 O 4 at (224 ± 2) K using time‐resolved infrared laser absorption

Direct kinetic measurements have been made on the reaction: 2NO 2 = N 2 O 4 . Equilibrium mixtures of NO 2 and N 2 O 4 at (224 ± 2) K were perturbed by flash photolysis of a fraction of the N 2 O 4 . The rate of relaxation back to equilibrium was monitored by observing the transmittance of the 14P(11) line from a cw CO laser selected to coincide with the v 9 band of N 2 O 4 . Measurements were made in the presence of 350–750 torr of He, N 2 , or CF 4 . Within this limited pressure range, the kinetics were consistent with third‐order behavior with the following rate constants (cm 3 molecule −1 s −1 ): k 0 = (2.4 ± 0.5) × 10 −34 [He]; (1.0 ± 0.1) × 10 −33 [N 2 ]; (1.8 ± 0.3) × 10 −33 [CF 4 ].