The continuous emission of an argon arc

The continuous emission of a wall-stabilised argon arc at atmospheric pressure was investigated at the wavelengths 255-700 nm. The electron density (7*10 22 -1.7*10 23 m -3 ) was obtained from laser interferometric measurements of the plasma refractivities at 632.8 and 1152.3 nm. Continuum xi factors were determined with a probable error of +or-8.5% on average. Agreement to within 15% was found up to 460 nm between the present experimental continuum data and published theoretical and experimental results. At longer wavelengths the experimental xi factors are noticeably dependent on temperature and are, in general, larger than theoretical values.