Generation of sodium and copper atoms in the gas phase by microwave-induced plasma afterglows

Abstract

A fast-flow reactor technique is described by which metal atoms in the gas phase can be produced in the afterglow of microwave-induced plasmas in hydrogen–helium or –argon mixtures. A metal compound MX brought into the gas phase by thermal sublimation can be converted rapidly in the afterglow to form metal atoms M which are detected by atomic absorption spectroscopy. Various parameters which influence the observed metal absorbance have been investigated such as the afterglow composition, the temperature and the axial distance in the flow reactor. Conditions are established for generating the relatively volatile sodium (3 ²S) and the non-volatile copper (4 ²S) atoms in the temperature range 300–800 K. For copper atoms a diffusion coefficient at 300 K and 10 Torr of 47.1 and 23.6 cm² s^–1 is derived in helium and argon, respectively. This system could become an interesting new source of metal atoms for kinetic studies of metal atom–gas reactions in the temperature range 300–800 K.