Long-lived Ar-Hg plasma in the afterglow of a high-current pulsed discharge

Abstract

High-density (n > 1012 cm−3) argon-mercury plasma produced by a short (t ∼ 20 μs) high-power pulsed discharge in argon with an admixture of mercury vapor at a discharge current of ∼50 A, an argon pressure of ∼4 mm Hg, and a mercury vapor pressure of ∼10−3 mm Hg was studied using optical spectroscopy and radio physics methods. It is found that the lifetime of this plasma after the end of the discharge pulse is up to 10−2 s. It is shown that such an abnormally long lifetime of such an afterglow plasma, as compared to the plasma of an argon discharge without an admixture of mercury vapor, is related to the long residence time of atoms and ions of both argon and mercury in highly excited states due to chemi-ionization processes involving long-lived metastable argon ions. It is suggested that dissociative recombination of highly excited molecular ions of argon play an important role in the transfer of excitation to argon atoms and ions that are close to autoionization states.