A spectral study of charge transfer and Penning processes for Cu, Zn, Ag, and Cd in a glow discharge

The occurrence of charge transfer and Penning process in glow discharge atomic emission sources can have a profound effect on the specific and overall spectral emission line characteristics of analyte species in these sources. A detailed spectral illustration of several of these effects is presented in this study for Cu, Zn, Ag and Cd with a particular focus on the ionic emission characteristics (i.e. II lines) of these elements. Charge transfer and Penning processes in glow discharge devices are driven by ionic and metastable species generated from the filler gas. Comparison of spectra obtained utilizing different filler gases is particularly effective for revealing the unique and specific excitation pathways for the analyte ions. Detailed high resolution spectra are presented and compared for Cu and Zn (brass) with Ar, Ne or He filler gases and for Ag and Cd with Ar or He as the filler gas illustrating several charge transfer and Penning processes. Unambiguous identification of spectral lines for specific transitions was facilitated by the acquisition of all spectral data utilizing a UV–visible Fourier transform spectrometer. This spectrometer provided complete and continuous coverage of the spectral region from 200 to 650 nm and allowed spectral lines to be identified with an accuracy of 1–2 pm.