Massenspektrometrische Analyse der Hg2 + -Bildung in der positiven Säule der Hg-Ar-Niederdruckentladung / Mass-spectrometric Analysis of Hg2 + Formation in the Positive Column of the Mercury-Argon Low Pressure Discharge

Abstract

The ions effusing ambipolar out of the positive column of a mercury-argon low pressure dis­charge are analyzed in a quadrupol mass spectrometer. Besides the Hg+-ion we find the Hg2 +-ion molecule. The measured current ratio i(Hg2 +)/i(Hg+) in the mass spectrometer is proportional to the mercury vapour pressure pHg in the discharge. i(Hg2 +)/i(Hg+) lies between 10-2 at pHg = 10-3 Torr and 1 at pHg = 0.1 Torr. - At constant argon- and mercury pressures i(Hg2 +)/i(Hg+) is inversely proportional to the discharge current. - At constant discharge current and mercury vapour pressures the ratio i(Hg2 +)/i(Hg+) is nearly independent of the argon pressure. An analysis of our measurements with the help of balance equations for excited Hg-atoms in the resonance level (3P1) and in the metastable 3P0 and 3P2 levels is carried out. It turns out that the only relevant process leading to the Hg2 +*ion molecule is the reaction Hg*+ Hg*→ Hg2 ++e of Hg-atoms in the levels 3P0, 3P1 and 3P2. It can be shown that the Hornbeck-Molnar-process Hg**+Hg → Hg2 ++e and the reactions Hg++2Hg→Hg2 ++ Hg, Hg++Hg+Ar→Hg2 ++Ar play an unimportant role in the Hg2 +-ion formation.