Behavior of ro-vibrationally excited H2 molecules and H atoms in a plasma expansion

P.J.W. Vankan, D.C. Schram, R.A.H. Engeln

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

1 Citation (Scopus)

Abstract

The behavior in a supersonic plasma expansion of H atom and H2 molecules, both ground-state and ro-vibrationally excited, is studied using various laser spectroscopic techniques. The ground-state H2 molecules expand like a normal gas. The behavior of H atoms and H molecules, on the other hand, is considerably influenced, and to some extend even determined, by their reactivity. The H atoms diffuse out of the expansion due to surface association at the walls of the vacuum vessel. Moreover, by reducing the surface area of the nozzle by a factor of two, the amount of H atoms leaving the source is increased by one order of magnitude, due to a decreased surface association of H atoms in the nozzle. The evolution of the ro-vibrational distributions along the expansion axis shows the relaxation of the molecular hydrogen from the high temperature in the up-stream region to the low ambient temperature in the down-stream region. Whereas the vibrational distribution resembles a Boltzmann distribution, the rotational distribution is a non-equilibrium one, in which the high rotational levels (J > 7) are much more populated than what is expected from the low rotational levels (J
Original languageEnglish
Title of host publicationProceedings of the 24th International Symposium on Rarefied Gas Dynamics, 10-16 July 2004, Bari, Italy
Pages1013-1018
DOIs
Publication statusPublished - 2005

Publication series

NameAIP Conference Proceedings
Volume762
ISSN (Print)0094-243X

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