IAPS,

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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_at_latnet.lv
• Web http//www.atomic-physics.lv

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Electrodeless lamps   

• ? Bright radiators in the broad spectral range
  (VUV - IR)
• ? Filled with a gas or metal vaporbuffer gas
• No electrodes long working life
• Inductive coupled/ capacitatively coupled
• Hf, Rf Electromagnetic field excitation
• Different designs and types in dependence on
  application

 
 
 
 
 
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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
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Examples
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Spectral line profile is important

• 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)

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Example of atomic absorption spectrometry

• Narrow, not self-absorbed spectral line is
  neccessary -- gt
• to get high differential cross section
  of
• atomic absorption --gt
• low limits of
  detection

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• 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

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Line profile measurements
High-resolution scanning Fabry-Perrot
interferometer
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High-resolution scanning Zeeman spectrometer for
resonance lines
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Hg 253,7 nm

• Natural filling Hg 202
  isotope

In dependence on the Tcold spot
On the working regime
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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
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Hg202/Ar(2 Torr) experimental and modeled
profiles of 253.7 nm line, spherical discharge
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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
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Hg202/Ar capillary
Experiment
Reff 0,8 (dninstr 0,071 cm-1).
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Hg202/Ar (10 Torr) capillary, 253.7 nm line,
Tcold spot 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
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Hg202/Ar (2 Torr) capillary, 253.7 nm line,
Tcold spot 65oC
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Comparison- spherical and capillary
160 mA and T cold spot 25oC, pAr10 Torr
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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 i100 mA. Fitted
parameters wG0,032 cm-1 wL0,002 cm-1 R0,72,
kol1,8, n13, using the model of Cowan and Dieke
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Example of the line shape fitting of 546.1 nm Hg
line, i140 mA. Fitted parameters wG0,033 cm-1
wL0,002 cm-1 R0,8 kol35 with taking into
account the measured distributions.

• Experimental radial distributions of Hg
  404.7 nm line intensity, emitted from HF
  electrodeless lamp by two different discharge
  power values.

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Helium example

• 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.

Experimental radial distributions of He 587,6 nm
line intensity, emitted from helium HF
electrodeless lamp by two different discharge
power values.
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• Thank you for your attention!

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