Spectroscopic characterization of low power argon microwave induced plasma

The spatial distributions of radiation densities emitted by various components (major, minor and traces) of atmospheric low power (100 W) argon microwave induced plasma (MIP), generated by a resonant TM010 cavity, were determined. The analytes (Ca, V and Zn) were introduced into the plasma in the form of aqueous solutions applying pneumatic nebulization. The obtained distributions were characterized by the value and the position of the maximum of radiation on the axis of the axially symmetric discharge of filament type. The distance of the maximum above the plasma torch depends on physical characteristics of the element. The influence of potassium on spatial radiation densities of all the mentioned species was investigated. The radial distributions of electron number density (1–9×1014 cm−3) were determined from the Stark broadening of the Hβ line. From the experimentally determined ratio of ionic to atomic spectral line intensity of Ca and electron number density, the radial distributions of the non-equilibrium factor, the degree of ionization of Ca and ionization temperatures of Ca, Tion(Ca), and of Ar, Tion(Ar), were determined. The values of Tion(Ar) are ranging from 6700 to 7600 K and of Tion(Ca) from 4000 to 5600 K in the plasma region from 1.6 to 3.4 mm in axial and up to 0.3 mm in radial direction. The obtained results compared with apparent temperature data from literature confirm that this plasma is not in state of local thermodynamic equilibrium (LTE).