Characterization of a capillary dielectric barrier plasma jet for use as a soft ionization source by optical emission and ion mobility spectrometry

Abstract

This paper presents the characterization of a source for soft ionization of organic molecules. This source is based on a plasma jet established at the end of a capillary dielectric barrier discharge at atmospheric pressure. He, Ne and Ar as pure gas or with different concentrations of N 2 are used as buffer gas for the plasma jet. Spectroscopic emission measurements are carried out along the plasma jet in and outside the capillary. The intensity variation of N 2 + lines, for example emission at 391.4 and 427.8 nm, can be associated with the protonation process which is the basis for the soft ionization. The mechanism of the N 2 + production outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated. The response signal of the ions in a nitrogen atmosphere was measured with an ion mobility spectrometer (IMS).