A one-temperature framework for the non-equilibrium dissociation of diatomic molecules, applied to H2 for giant-planet entry flows. Starting from the rovibrational master equations, the chemical source term in the QSS regime reduces to a function of the non-recombining dissociation rate constant kd,nr(Tt) alone; pre-QSS incubation effects are captured by one extra fitted rate term eta(Tt) derived from an eigenvalue analysis of the rate matrix. The model reproduces detailed master-equation simulations for third-bodies H2, H, and He, and an extensive review of shock-tube, discharge-flow-tube, and computational data yields new kd,nr/Keq fits per third-body valid from 200 to 20,000 K, superseding the widely used Leibowitz rates.
This work presents a detailed description of the thermochemical non-equilibrium dissociation of diatomic molecules, and applies this theory to the case of $\rm H_2$ dissociation. The master equations…