The hollow cathode lamp (HCL) has been used for decades as a stable, intense source of narrow-line radiation. In recent years, there has been renewed interest in HCLs, or other glow discharge lamps, since they have been shown to be useful emission sources. Although the intensity produced by conventional HCLs is sufficient for many applications, there have been a number of efforts to design lamps with increased intensity spectra. Enhanced performance has been achieved with microwave or radio-frequency-boosted discharges, pulsed operation, furnace atomization, etc. Developments in glow discharge properties and applications have recently been reviewed and have been the subject of two special issues of Spectrochimica Acta.
T. M. Niemczyk, B. D. Thompson, and J. E. Angus, "Intensity Enhancements in Hollow Cathode Lamps Due-to the Addition of Nitrogen to the Fill Gas," Appl. Spectrosc. 48, 896-899 (1994)