Darmstadt 2008 – scientific programme
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P: Fachverband Plasmaphysik
P II: Poster: Niedertemperaturplasmen, Plasmatechnologie
P II.25: Poster
Tuesday, March 11, 2008, 11:00–13:00, Poster C3
Population Inversion of Excited Hydrogen Atoms in a Recombining Hydrogen Plasma Jet — •Onno Gabriel, Suleiman Elhamali, Jeroen van den Dungen, Daan Schram, and Richard Engeln — Department of Applied Physics, Plasma & Materials Processing, Technische Universiteit Eindhoven, Postbus 513, 5600 MB Eindhoven, The Netherlands
The densities of hydrogen ions and atoms in an expanding thermal hydrogen plasma jet can be strongly increased by applying an axial magnetic field. This well known technique of confinement is used for the generation of large ion flows. Our research is focused on hydrogen plasma-surface interactions, for which we use the magnetized plasma jet as an atom source. Under certain plasma conditions an interesting feature is visible: The emission of the plasma jet, dominated by Hα lines at the first centimeters, changes to the blue spectral region due to higher Balmer lines (n > 4). Moreover, these higher electronic states of H atoms become stronger populated than the lower states. A possible reaction route resulting in the formation of these high excited hydrogen atoms is via mutual recombination of positive and negative ions. The latter are formed by dissociative attachment of electrons with rovibrationally-excited hydrogen molecules, which we measured spatially and internal state resolved by laser induced fluorescence in the VUV. TALIF on ground state hydrogen atoms completes the picture. These measurements indicate the high degree of excitation of these expanding plasmas, and the possible importance of rovibrational-excited molecules and negative ion formation.