Characterization of Bromine and Chlorine Atomic Emission in a Reduced-Pressure Inductively Coupled (27 MHz) Helium Plasma

Abstract

A reduced-pressure 27 MHz inductively coupled plasma (ICP) sustained in helium at low powers (less than 300 W) has been investigated with regard to future application as a selective halogen detector for gas chromatography. The effects of applied power and bulk gas flow rate on neutral and monopositive ionic chlorine and bromine plasma species have been studied. Studies of the optical emission spectra of helium plasmas containing low-molecular-weight organohalogens show that the molecular fragments of the analyte give rise to little radiative background interference. Quantitative results for halogen atomic state populations show that the monopositive species exist in an effectively much hotter plasma environment than the neutral species. A listing of corrected spectral intensities for the most prominent halogen emissions observed from the rf helium plasma over the region 2500 to 7500 Å are given as an appendix.