Technique for Distinguishing and Determining the Origin of Photon Emissions from He⁺/Ar⁺ Plasmas

Abstract

Experimental studies of electron-ion recombination have traditionally been made in three ways: (1) the determination of recombination rate coefficients, some as a function of temperature, (2) the identification of ground state neutral products and (3) the detection of excited state products. Initial studies of (1) were made in stationary afterglows, predominantly by Biondi and co-workers1 and Smith and co-workers2 and were followed by investigations using the more versatile flowing afterglow.3 In parallel with the latter studies, emission spectroscopy was used primarily for detecting excited state products in ion- and metastable-neutral reactions,4–6 but with some studies in which excited products of recombination were detected. Studies were later made by Adams and co-workers7,8 and by Johnsen and co-workers9 to detect the ground state products of recombination, a more difficult problem but where substantial progress has been made. At the same time, determination of product distributions was also starting in storage rings.10,11 In this area, storage ring studies have been more numerous, due predominantly to the degree of effort put into the technique by a number of workers. Also, with this method, it is possible to inject a single ion species into the ring, and for heteronuclear ions to radiationally cool the vibrations.12 In the flowing afterglow, it is more complicated to create a single ion plasma, ensure that the ions are vibrationaly relaxed and to detect all of the products simultaneously.