On the importance of N4+ ions in the chemistry of a He-N microjet discharge

The microdischarges under atmospheric pressure do not require expensive vacuum equipment and therefore are potentially advantageous for industrial and biological applications. The experimental diagnostics options are however rather limited due to the small size of the microdischarges and numerical modeling is thus very useful for understanding of the processes taking place there. One of the examples frequently treated in the literature is a He-N microjet discharge driven by an RF voltage source. Most of the treatments in the literature do not include the N4+ cluster ions in their chemistry sets. We demonstrate, by modeling a He-N microjet discharge with a hybrid code which treats electrons kinetically and ions using a fluid description, that N4+ ions tend to be the dominant ion species in such a discharge even for small fractions of He. We also discuss several additional interesting features of the discharge.