Population dynamics of molecular hydrogen and formation of negative hydrogen ions in a magnetically confined low temperature plasma

Abstract

An attempt is made to unravel the influence of vibrational population distributions of molecular hydrogen in the electronic ground state on the formation of negative hydrogen ions in the volume of a magnetically confined low temperature plasma. The densities of rovibronically excited molecules are determined by laser-induced fluorescence spectroscopy and optical emission spectroscopy. Energy distributions of electrons are measured with a Langmuir probe and densities of negative ions are found by laser-induced photodetachment. A global model is presented that describes the stationary state of the molecular plasma. An overall view of the discharge is obtained on the basis of this model. This allows us to cross-check the obtained results for coherence. It also allows us to assess the relevance of specific processes and their dependences on the rovibronic molecular states and the discharge current. The influence of associative recombination of a hydrogen atom of the plasma bulk with a hydrogen atom adsorbed at the wall is discussed with respect to the influence of this process on the densities of other plasma particles, in particular the density of the negative ions.