Equilibrium density of H- in a low pressure hydrogen plasma

The equilibrium density of hydrogen negative ions in a hydrogen low pressure plasma was calculated taking into account the various known production and destruction processes. It is shown that in most plasma conditions the contribution of dissociative recombination to H- production is essential. Due to this process higher H- densities are calculated than those obtained when dissociative electron attachment only is considered. However the calculated densities are approximately 100 times lower than the experimental values found in low pressure hydrogen plasmas. This discrepancy suggests that the dominant negative ion formation process in hydrogen plasma has not yet been identified