VUV-Photoionisation Chamber for the Characterization of Ion-Substrate Interactions at Atmospheric Pressure*

The strong interaction between cold atmospheric pressure plasmas and biological substrates is, besides the reactive oxygen and nitrogen species, also based on additive or synergistic effects of these reactive species with charged species, photons, and electric fields. In contrast to photons or electric fields, the study of the isolated effect of ions with biological substrates is more challenging as their solely production under atmospheric pressure is not trivial. To prove the expected enhanced effect of ions due to their charge and internal energy, knowledge about the ion composition and absolute ion fluxes to the substrate is needed.

To study the isolated interaction of ions with substrates, an experimental setup has been developed in which photoionized ions are directed towards the biological substrate. The ions are generated in a helium atmosphere with a small admixture of Ar, O₂ or other gaseous species by VUV radiation of the helium excimer emission (60-100nm) generated by a helium driven atmospheric pressure plasma. Mass spectra and relative ion fluxes along the substrate position are measured by ion mass spectrometry. Combined with spatial resolved current measurements, the absolute ion flux can be determined.