Modelling of spectral line shapes in electrodeless discharge lamps

1. Modelling of spectral line shapes in electrodeless discharge lamps G. Revalde1, N. Denisova2,A.Skudra1 1 High-resolution spectroscopy and light source technology laboratory, Institute of Atomic Physics and Spectroscopy, University of Latvia 2 Institute of Theoretical and Applied Mechanics, Novosibirsk, Russia E-mail: gitar@latnet.lv Web: http://www.atomic-physics.lv IAPS, University of Latvia

2. Electrodeless lamps:    • Bright radiators in the broad spectral range (VUV - IR); •  Filled with a gas or metal vapor+buffer gas; • No electrodes – long working life • Inductive coupled/ capacitatively coupled; • Hf, Rf Electromagnetic field excitation; • Different designs and types in dependence on application IAPS, University of Latvia

3. Our experience and technology:   manufacturing of electrodeless lamps containing such elements as Sn, Cd, Hg, Zn, Pb, As, Sb, Bi, Fe, Tl, In, Se, Te, Rb, Cs, I2, H2, He, Ne, Ar, Kr, Xe as well as combined Hg-Cd, Hg-Zn, Hg-Cd-Zn, Se-Te etc (also isotope fillings, as example Hg202) etc. for different applications IAPS, University of Latvia

4. Examples IAPS, University of Latvia

5. to control self-absorption or radiation trapping for design consideration of low pressure lamps for lighting application - resonance radiation of Hg at 185 nm and 254 nm in all cases when narrow spectral line is necessary – for atomic absorption, optical pumping, quantum standards, for spectral reference to get important plasma parameters (such as gas temperature, lower state density, collisional broadening) Spectral line profile is important IAPS, University of Latvia

6. Narrow, not self-absorbed spectral line is neccessary -- > to get high differential cross section of atomic absorption --> low limits of detection Example of atomic absorption spectrometry IAPS, University of Latvia

7. But with self-absorption dependent on working regime filling pressure, filling content lamp geometry excitation geometry Possibilty to avoid the self-absorption – optimisation of all parameters IAPS, University of Latvia

8. Vacuum chamber Amplifier Lens Lens Fabry – Perrot interferometer Lamp Computer Photomultiplier Capillary Capillary Monochromator Power supply Lineprofile measurements High-resolution scanning Fabry-Perrot interferometer IAPS, University of Latvia

9. High-resolution scanning Zeeman spectrometer for resonance lines IAPS, University of Latvia

10. Natural filling Hg 202 isotope Hg 253,7 nm In dependence on the Tcold spot On the working regime IAPS, University of Latvia

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15. Examples of experimental and modeled profiles Zeeman spectrometer Fabry-Perrot spectrometer Necessity to take into account the instrument function, also by a small FWHM value of instrument profile due to the influence on the self-reversal IAPS, University of Latvia

16. Hg202/Ar(2 Torr) experimental and modeled profiles of 253.7 nm line, spherical discharge IAPS, University of Latvia

17. Example, Hg 202(99.8 %) 253,7 nm line 160 mA, Tc.spot.=72oC 50 mA, Tc.spot.=72oC Distribution of the intensitites other isotopic components (0.2 %) also fitted IAPS, University of Latvia

18. Hg202/Ar capillary Experiment Reff = 0,8% (dninstr =0,071 cm-1). IAPS, University of Latvia

19. Hg202/Ar (10 Torr) capillary, 253.7 nm line, Tcoldspot= 25oC The total experimental spectral line FWHM as a function of the HF generator current The estimated temperature of the emitting atoms The estimated optical density in the line center IAPS, University of Latvia

20. Hg202/Ar (2 Torr) capillary, 253.7 nm line, Tcoldspot= 65oC IAPS, University of Latvia

21. Comparison- spherical and capillary 160 mA and T cold spot =25oC, pAr=10 Torr IAPS, University of Latvia

22. Hg visible triplett Experimental 404.7 nm line shapes in dependence on the HF generator current for a HF isotope electrodeless lamp Example of the line shape fitting of Hg 404.7 nm line, HF generator current i=100 mA. Fitted parameters wG=0,032 cm-1; wL=0,002 cm-1; R=0,72, kol=1,8, n=13, using the model of Cowan and Dieke IAPS, University of Latvia

23. Experimental radial distributions of Hg404.7 nm line intensity, emitted from HF electrodeless lamp by two different discharge power values. Example of the line shape fitting of 546.1 nm Hg line, i=140 mA. Fitted parameters wG=0,033 cm-1; wL=0,002 cm-1; R=0,8; kol=35; with taking into account the measured distributions. IAPS, University of Latvia

24. Optical density in the line center in dependence on the HF generator current estimated for 501,6 nm and 567,8 nm lines in the helium electrodeless discharge using the model of uniformly excited source. Helium example Experimental radial distributions of He587,6 nm line intensity, emitted from helium HF electrodeless lamp by two different discharge power values. IAPS, University of Latvia

25. Thank you for your attention! IAPS, University of Latvia

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