The percentage error in the depletion delay is within 15% for the entire range of temperature of interest to hypersonic applications. Altogether, the reference O 2 mole fractions and those predicted using SurQCT closely agree. The same can also be stated for the energy evolutions in Fig. , which show excellent accuracy also in the QSS regions (i.e., the small plateaus). To accurately describe non-equilibrium phenomena in a chemically reacting system, it is also essential to predict the StS population distribution with high fidelity. For this purpose, a comparison is made for the QSS population distribution at two translational temperatures, 8, 000 and 20, 000 K (Fig. ). The figure also reports the errors in the logarithm of the population plotted over the diatomic potential. These last quantities are computed as: