An Investigation of the Positive Column of a Cd–Ne Glow Discharge. I: Steady State

An investigation of cadmium-neon plasma in cylindrical axially homogeneouspositive column of a dc glow discharge at low and intermediate pressure ispresented. Electron impact excitation cross sections, heavy-particlecollision rate coefficients, and radiative decay rates for Cd–Nemixture have been assembled from the literature and summarized. Aself-consistent collisional-radiative model based on numerical solution ofthe electron Boltzmann equation coupled with a system of particle balanceequations for the electrons, excited atoms and ions, as well as the electronenergy balance equation, is developed. By this model, the electron energydistribution function, mean energy, electron density, electron mobility, anddiffusion coefficient, populations of Cd and Ne excited states and theapplied dc electric field are calculated. The populations of the excitedCd(5p3P0,1,2) atoms are measured using opticalabsorption spectroscopy. From these measurements the effective lifetime ofthe resonance state Cd(5p3P1) and the diffusioncoefficients of both metastable states Cd(5p3P0) andCd(5p3P2) are determined. The electron density isderived by probes measurements. The influence of the Cd vapor pressure anddischarge current on the main plasma characteristics is studied. Modelpredictions compare favorably with measured electron density and populationsof excited states in a wide range of discharge conditions.