Pressure Broadening of Multiply Ionized Carbon Lines

Abstract

Abstract In a helium plasma with carbon impurity, the pressure broadened profiles of seven C III and two C IV lines have been measured. The plasma which was produced by magnetic compression had typically an electron density of 4 · 1017 cm-3, a temperature of 60 000°K, and a life time of about 0.1 μs. Electron densities have been deduced from the width of the He II λ= 3203 Å line. If ΔEii′ ≪ kT {ΔEii′ = energy difference between perturbed level i and perturbing level i′) the classical straight line non-adiabatic theory gives values being in good agreement (error < ± 25%) with measured widths for six lines. For two lines the deviations are larger. For the C IV resonance line (λ = 1550 Å) with ΔEii′ >k T, the profile can be explained by hyperbolic path, adiabatic collision theory. The semiempirical Gaunt-factor approximation gives a rough estimate of the width, but normally the values obtained are too low.