Light scattering from Ne, Ar, and Xe arcs

A procedure is described whereby nonresonant polarized and depolarized Rayleigh, electronic Raman, and Thomson scattering are used as a diagnostic tool for high-pressure nonhomogeneous plasmas. The method is applied to 0.1–3 atm Ne, Ar, and Xe arcs, with currents not exceeding 3 A. Polarized Rayleigh scattering is dominant in these cases. Radial gas temperature and density distributions, an axis electron density, and upper limits of excited state and electron densities are obtained. The temperature range covered extends from about 350 K (near the wall) up to 4500 K (at the axis of a 2-A 3-atm Ne arc). A comparison with spectroscopically obtained temperatures is shown to yield interesting information on the deviations from local thermodynamic equilibrium.