Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 10: Posters Wednesday (Cooling and Trapping, Electron Scattering and Recombination)

A 10.32: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT3

Stationary afterglow study of recombination of H₃⁺ ions with electrons — •Juraj Glosik, Radek Plasil, Viktoriya Poterya, Pavel Kudrna, Andriy Pysanenko, Milan Tichy, and Jan Rusz — Charles University Prague, Mathematics and Physics Faculty, Department of Electronics and Vacuum Physics, V Holesovickach 2, 180 00 Prague 8, Czech Republic

The rate coefficient of the recombination of H₃⁺ ions with electrons, α, has been measured at 270 K in stationary afterglow experiment. Strong dependence of an apparent recombination rate coefficient, α_eff, on the number density of added neutral H₂, n(H₂), was obtained. At high number densities, n(H₂) > 5×10¹² cm⁻³ the apparent rate of the recombination is approaching value α_eff ∼ 2×10⁻⁷ cm³s⁻¹. With decreasing n(H₂) down to 6×10¹⁰ cm⁻³ the observed recombination rate coefficient is decreasig down to α_{eff LIMIT} < 4×10⁻⁹ cm³s⁻¹. The obtained nearly linear dependence of α_eff on n(H₂) can indicate that the H₃⁺ ions are removed from the plasma in a three body process. We assume that in the first step of this process the highly excited H₃^* is formed in collision of H₃⁺ ions with electrons. The recombination process is completed by collison of H₃^* with present H₂ which prevents autoionisation of H₃^* back to ion and electron.

The actual, for interstellar space relevant, No-dqbinaryNo-dq recombination rate coefficient α < α_{eff LIMIT} = 4×10⁻⁹ cm³s⁻¹. This is in the agreement with theoretical predictions and recent astronomical observations.