Measurement of the Electron-Impact Broadening of Ionized Nitrogen and Carbon Resonance Lines in a High-Pressure Electric Shock Tube

Abstract

Profiles of the overlapping fine-structure components of C II and N II vacuum ultraviolet resonance lines emitted from optically thick shock-heated layers consisting mostly of helium were measured on a shot-to-shot basis, using a $T$-type electromagnetic shock tube as a source. Plasma conditions were determined from spectroscopic measurements in the visible region. The analysis was based on a radiative transfer model for the resonance multiplets, assuming superimposed Lorentzian profiles with known oscillator strengths and the existence of local thermodynamic equilibrium. The resulting damping constants are interpreted as due mainly to elastic electron collisions and agree within factors of ∼ 1.0 and ∼ 1.5, respectively, with predictions based on a semiempirical method.