Abstract
The spatial distributions of metastable densities and optical emissions were measured in the cathode region of He glow discharge over the current density range 0.15-2.2mA/cm2 at 12 Torr. In the negative glow, the light is emitted not only by the cause of direct excitation but also by recombination of atomic and molecular ions. The metastable atom densities were measured by absorbtion method, and the two sort of metastable atom, He (21S) and He (23S), distribute in quite different manner. In the cathode region, it is difficult to determine the absolute production rate of metastable atoms theoretically, but it is more easy to determine the relative distribution shapes of them from the atomic line distributions. Therefore, using the spatial distributions of relative production rate, the measured density distributions and the known rate constants of destruction of metastable atoms, the absolute production rates of metastables can be estimated. The ratio of two production rates agrees well with the result from Monte Carlo simulation.
