1. Reference 14 shows that the vibrational relaxation rates become smaller at high post-shock temperatures than those predicted by the Landau-Teller equation. The Landau-Teller equation correctly describes the excitation of first vibrationally excited state (v = 1) from the ground state (v = 0). This (0-1)transition is the only significant excitation process occurring at low temperatures, that is, when the average translational energy of the gas molecules is of the order of the vibrational energy gap. In this case, the vibrational relaxation rate varies linearly with the temperaturedifference T - T, as described by the Landau-Teller equation. If the average translational energy is significantly higher than the vibrational energy gap, the Landau-Teller equation is obeyed only in the region immediately behind the shock wave where most of the molecules are still in their vibrational ground state. At finite distances away from the shock wave, many vibrational states become significantly excited so that collisions cause transitions of these states in both upward and downward directions. The rate of change of population of any of these excited vibrational states then becomes equal to a small difference between two large rates, that is, the difference
2. In Fig. 2, the calculated radiation spectrum is compared with the measured spectrum in the equilibrium region for the case of 0, = 1.498 x g/cm 3 (10 torr pressure) and u_ = 4.8 lon/sec. Both calculation and experiment were made at 200-8 intervals using monochromator with a wavelength bandwidth of 200 8 starting at 3100 H. As seen here, the measured data are reproduced by the calculation Fairly accurately, that is,within the accuracy of the measurement. This adds support to the method of computing radiation using the NEQAIR program, at least for known thermodynamic conditions.