Studies of reactions of importance in the stratosphere. VI. Temperature dependence of the reactions O+NO2→NO+O2 and O+ClO→Cl+O2

Abstract

Articles you may be interested inStudies of reactions of importance in the stratosphere. V. Rate constants for the reactions O+NO2→NO+O2 and O+ClO→Cl+O2 at 298 K J. Chem. Phys. 81, 3922 (1984); 10.1063/1.448185 Studies of reactions of importance in the stratosphere. IV. Rate constant for the reaction Cl+HOCl→HCl+ClO over the temperature range 243-365 K J. Chem. Phys. 74, 545 (1981); 10.1063/1.440807The temperature dependence of the NO-O chemiluminous recombination. The RMC mechanismThe reactions of two free radicals, nitrogen dioxide and chlorine monoxide, with oxygen atoms, 0 + N0 2 -NO + O 2 and 0 + CI~1 + O 2 , have been investigated in a fast flow system over the temperature range 220-387 K, at a total pressure of 2.3 Torr. Reaction rates were measured under psuedo-first-order conditions with either CIO or N0 2 in large excess and the decay of oxygen atoms monitored by adding nitric oxide at the end of the flow tube and detecting the 0 + NO + M chemiluminescence. The reactions are of interest, because they are thought to be the rate determining steps in two catalytic chains which destroy odd oxygen (0 and 0 3 ) in the stratosphere. Measurements of the rate constants over the stated temperature interval yielded the Arrhenius expressions ko+ N0 2 = (6.58 ± 0.52) X 10-12 ~p[ (142 ± 23)/ T] and k O + C10 = (2.61 ± 0.60) X 10-11 exp[(97 ± 64)/T]. Thus, both reactions display small negative activation energies. In addition, experiments showed no pressure effect on the reaction rate in the range 2.3-5.3 Torr and at a temperature of 230 K. Addition of a partial pressure of 1 Torr of oxygen also had no effect on the rate constant at 230 K, suggesting that CIO • O 2 formation is of little or no significance under stratospheric conditions.

Rate constants of the reactions of O(3P) atoms with Br2 and NO2 over the temperature range 220‐950 K

“…Figure summarizes the results of temperature‐dependent measurements of the rate constant of reaction . Westenberg and deHaas have measured the reaction rate constant at T = 297‐543 K in a fast‐flow reactor combined with electron spin resonance spectroscopy.…”

“…Besides the atmospheric importance, the reaction is often used in laboratory studies as a titration reaction of oxygen atoms and is included in NO 2 submechanism of kinetic models for combustion systems . Hence, it is not surprising that kinetics of the reaction has been studied very extensively in the past . Currently, the rate constant of the O + NO 2 reaction, k 1 , can be considered as well established in the temperature range T = 220‐425 K .…”

Dynamics of the O + ClO Reaction: Reactive and Vibrational Relaxation Processes

“…Replacing the sampling procedure in eq 6 for a set of N integrated trajectories, the QCT thermal rate constant can be calculated by (12) where b max is the maximum impact parameter, and P k = N k /N is the probability of populating the kth channel. Statistically, 68% of associated error is then given by Δk(T) = k(T)[(N − N k )/ (NN k )] 1/2 , where N k , in the above expressions, is the number of trajectories leading to the kth molecular arrangement.…”

An experimental and theoretical study of the reaction of ethynyl radicals with nitrogen dioxide (HC≡C+NO2)

“…The term k 7 Ј is however a function of ͓NO 2 ͔, but since k 7 is well established over the temperature range of our experiments [63][64][65][66][67][68] and since ͓NO 2 ͔ is known from flow calibrations, it may be readily calculated.…”