Spectral intensities as a function of Hg content and measurement position in fluorescent light tubes

Summary form only given. Spectra were recorded from a fluorescent light tube under a number of experimental conditions and using different spectroscopic techniques. The motivation of the work was to use spectroscopic techniques for plasma diagnostics purposes. The spectrometers used were a high resolution echelle based instrument and a Fourier transform spectrometer in Lund and a low-resolution instrument in Toulouse. The interest in the low resolution instrument is that it is attached to a temperature controlled bath. The data obtained in Lund was at much higher resolution but not temperature controlled. Spectra were also recorded at a number of positions along the tube. Some of the results can be summarized as follows: (a) spectral lines from ionized Hg decay much faster as a function of temperature than lines from Hg I. This is in some ways unexpected as: (b) the percentage of excited noble gas atoms increases as the lamp temperate, i.e. Hg atom content, goes down, which would appear to indicate that; (c) the electron energy increases as the Hg content (lamp temperature) goes down; (d) From the intensities of noble gas lines as a function of distance from the filament it would appear that the electron temperature is higher close to the filament. One would imagine that the concentration of excited Hg⁺ would benefit from a higher electron energy distribution or a higher content of excited noble gas atoms (Penning ionization/excitation). Hence one may expect the Hg⁺ excited concentration to follow that of excited Hg, but such is not the case. Some of the above mentioned conclusions, e.g. (c) and (d) are known in the literature from other experimental studies. The other points are the subject of further studies using a combination of high spectral resolution, controlled temperature and time resolved methods