Thermal dissociation of diatomic molecules

The establishment of equilibrium in the chemical reaction X2+M ⇄ ⇄ 2X+M is examined. All possible transitions between the vibrational levels and the continuous spectrum are considered. Taking account of two relaxation times, an expression is obtained for the concentration of the X atoms and the chemical reaction rate as a function of time. The conditions under which the dependence of the chemical reaction rate on time acquires an exponential nature are determined. An expression free from the requirement that the initial concentrations of X-atoms and X2 molecules should be close to their equilibrium values is obtained for the rate constant.