Density and production of NH and NH 2 in an Ar-NH 3 expanding plasma jet

Abstract

The densities of NH and N H2 radicals in an Ar-N H3 plasma jet created by the expanding thermal plasma source were investigated for various source-operating conditions such as plasma current and N H3 flow. The radicals were measured by cavity ringdown absorption spectroscopy using the (0,0) band of the A Π3 ← X ∑-3 transition for NH and the (0,9,0)-(0,0,0) band of the à A12 ← X̃ B12 transition for N H2. For NH, a kinetic gas temperature and rotational temperature of 1750±100 and 1920±100 K were found, respectively. The measurements revealed typical densities of 2.5× 1012 cm-3 for the NH radical and 3.5× 1012 cm-3 for the N H2 radical. From the combination of the data with ion density and N H3 consumption measurements in the plasma as well as from a simple one-dimensional plug down model, the key production reactions for NH and N H2 are discussed. © 2005 American Institute of Physics.