Radiative Recombination of Chlorine Atoms in Shock Waves

The equilibrium emission behind shock waves in Cl2–Ar mixtures has been measured as a function of temperature, wavelength, and atom concentration. The emission spectrum has been recorded at 2200°K and the absolute rate of emission has been measured in two regions of the visible spectrum. The emission is found to behave in adequate accordance with a theory based on calculation of the equilibrium concentrations of molecules in excited states. However, it is necessary that the radiative lifetime of the 3Π0+u state be considerably shorter than previously thought. It appears to be a few microseconds, i.e., of the same order as the 1Π1u.