Some observations on small-size electrodeless discharge lamps for strontium used for Zeeman scanning of absorption line profiles in flames

Abstract

Microwave-excited electrodeless discharge lamps (EDL) for Sr were produced and a technique was developed for stabilizing the microwave power. Some characteristics of the EDL were investigated. The lamps were compared with a normal (= non-boosted) commercial hollow cathode lamp (HCL). Half-intensity widths of the Sr-line at 4607.33 Å were determined by interferometry for EDL and HCL sources under various operating conditions. Moreover, with both sources peak absorption measurements were carried out in a flame with Sr vapor; the results obtained by either technique were partially mutually consistent. Selected samples of EDL gave half-intensity widths of about 7–10 mÅ, independent of microwave power. The line width of the HCL increased from about 7 to 20 mÅ with increasing current up to 26 mÅ (= maximum rating). The radiance of the EDL's (at 50 W) was about the same as that of the HCL, when the latter was operated at 10 mA to give a comparable half-intensity width of 10 mÅ. At maximum microwave power the radiance of the EDL appeared to be 15–20 % of that of the HCL at maximum current, but the EDL line width remains only 7–10 mÅ, whereas that of the HCL line is about 20 mÅ and the HCL line is heavily self-reversed. EDL's with radiance values 10–100 × higher than that of the HCL at 25 mA were also produced; the high radiance value is obtained by increasing the Sr content in the EDL drastically. The profile of the EDL line has then a width of about 60 mÅ and the line is heavily self-reversed. Some tentative results on stability and life of the EDL's are reported.