Complementary optical diagnostic modelling of the argon positive column

The argon positive column has been investigated by means of a complementary diagnostic approach, which combines the CW laser collisionally induced fluorescence (LCIF) technique with kinetic models for the excited-state populations and emission line ratios. The conditions ranged from pressures of 0.30-8.0 Torr and currents of 1-10 mA, equivalent to reduced axial electric fields of 1.7-53 Td. Fitting theory to experimental observations of the Is densities and 2p-1s emission intensities allows determination of the electron temperatures relating to the high-energy electrons in the tail of the electron energy distribution function. The tail temperatures vary from 0.9 to 1.9 eV over the range of conditions investigated. Examination of CW LCIF for 1s(5)-2p(2) (696.5 nm) laser excitation along with the traditional optical absorption and emission techniques provides specific information on the collisional kinetics involving the metastable states.