PUMPING OF HIGHLY VIBRATIONALLY EXCITED MOLECULES IN A HYDROGEN FLOW-THROUGH A CESIUM-HYDROGEN DISCHARGE

There is a considerable interest in the creation of vibrationally exci ted H-2 molecules because of their application to H- ion volume-plasma sources, plasma chemistry etc. It has been shown that a tow-voltage d ischarge in a Cs-H-2 mixture might be used as an effective source of v ibrationally excited H-2 molecules. In this paper it is shown that the vibrational distribution function (VDF) of H-2 molecules may be signi ficantly improved if vibrational excitation occurs in a moving flux of H-2 molecules penetrating through the discharge. The following theore tical model is considered. Hydrogen flux flows in a flat channel and p asses successively through two sections. Section I is a discharge sect ion, where low-voltage Cs-H-2 discharge occurs and vibrationally excit ed H-2 molecules are created. In section II, the excited hydrogen flow s in a plane channel, with cold walls. Because of the large value of t he mean vibrational energy of a H-2 molecule, a significant intensific ation of the H-2 high vibrational level population takes place in sect ion II. This intensification is of the order of 10(3)-10(4) for severa l vibrational levels. The increase of the vibrational level population occurs due to the diffusion of vibrational quanta, by v-v exchange, u p to high vibrational levels. The VDF, obtained at the exit of section II, is significantly improved for the purposes of H- generation by me ans of dissociative attachment.