Molecule formation in plasma at surface

With diode laser spectroscopy and mass spectrometry the generation of new molecules is studied in two types of plasmas: an expanding thermal plasma at TU/e and a microwave discharge at INP. Molecules formed in argon plasmas with N, H, O and C containing molecules were measured in a two laboratory study. Flows, pressure and power were designed such that an appreciable portion of the admitted gases could be dissociated. The results are very similar: predominantly H$_{2}$, N$_{2}$, CO, H$_{2}$O and/or O$_{2}$ are formed and to a lesser extent, NO, HCN and NH$_{3}$, C$_{n}$H$_{m}$ and CO$_{2}$. Also H$_{2}$CO is observed. Surface generation is concluded for most of the observed molecules. The surface is passivated with radicals from the plasma and the abundances of specific precursor adsorbants as H, N, OH, NH$_{2}$, NO, CH$_{3}$ etc. is apparently important for the production of new molecules. Observation of excited species as H$_{2}$(r,v), N$_{2}$* and NO$_{2}$ (shuttle glow) near to surfaces at high fluxes of radicals forms a further support for the surface production mechanism.