Driftgeschwindigkeiten, Diffusionskoeffizienten und Temperaturen von Photoionen in Argon, Stickstoff und Sauerstoff / Drift velocities, diffusion coefficients and temperatures of photo-ions in argon, nitrogen and oxygen

Abstract

Abstract Groups of ions were produced by photoionisation of argon, nitrogen and oxygen in a drift chamber, using as the light source a repetitive spark discharge in combination with a uv monochromator. After their traversal of the drift region, the ions were detected in a mass spectrometer. An analysis of the temporal arrival profiles provided ionic drift velocities and diffusion coefficients as a function of gas pressure and electric field. For ions in their electronic and vibrational ground states, the measured drift velocities are in accord with previous data in the literature. At some wave lengths excited ions are produced in addition to ground state ions. Their drift velocities are larger on account of smaller charge transfer cross sections. Drift velocities and diffusion coefficients pro-vide ion temperatures as a function of the reduced field strength. Ion temperatures for argon ions correspond to the gas temperature. For nitrogen and oxygen ions the temperatures increase linearly with E/P and extrapolate at high fields to those given by Wannier's theory