Ion conversion in an argon afterglow

Abstract

A 9 GHz free-space microwave interferometer was used to measure the electron density decline over the range 10¹¹-10¹⁰ cm⁻³ in the afterglow of a pulsed argon discharge in a 127 cm diameter cylindrical tube (characteristic diffusion length Λ=246 cm). In the range 014-061 torr the results are interpreted in terms of the ion conversion mechanism Ar⁺+2Ar->Ar₂⁺+Ar. The conversion frequency, found to be 376_p0² s⁻¹ (p0 being the pressure reduced to 273°K), is compared with the available theoretical values. Owing to the high electron density and large-diameter discharge tube the present method is more suitable for the measurement of this parameter in argon than were previous microwave studies.