A study of argon metastable generation in a hollow cathode arc

A study is made of the intense spectroscopic continuum obtained between 120 and 180 nm for an argon–helium mixture (15% He) deexcitation, the emission originating from a hollow cathode arc discharge operated at 2900 K and a calculated pressure of 20 kPa. The deexcitation of the excimers toward the repulsive fundamental level gives way to an ultraviolet (UV) continuum, which is a characteristic of the potential energy curve for these molecules and whose position in the wavelength scale depends on the temperature of the hollow cathode. This continuum is identified as the second Tanaka continuum.Absolute radiation measurements have been made with a gold coated photocathode in order to determine the excited rare gas molecules [Formula: see text] concentration, which is in the order of 7 × 1013 cm−3.Such concentrations are high and seem to be related to the generation means used (hollow cathode).The spectroscopic results obtained with the indicated specific argon–helium mixture imply a major contribution of a precursor of the type (He–Ar)+ for the [Formula: see text] metastable formation.