Light related activities at High resolution and light source technology laboratory, Institute of Atomic Physics and Spectroscopy, Riga

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Light related activitiesat High resolution and
light source technology laboratory,Institute of
Atomic Physics and Spectroscopy, Riga
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• Institute of Atomic Physics and Spectroscopy

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Laboratory is a part of the Institute of Atomic
Physics and Spectroscopy

• Members
• Dr. Atis Skudra (head)
• Dr. Imants Bersons
• Dr. Gita Revalde
• Eng. Juris Silinš
• PhD students
• Natalja Zorina,
• Egils Bogans,
• Zanda Gavare,
• Mr. Martinš Berzinš

• Collaboration partners
• Institute of Theoretical and Applied Mechanics,
  Novosibirsk, Russia
• CPAT, Toulouse, France
• Institute of Non-thermal plasma physics,
  Greifswald, Germany
• University of St.Petersburg, Russia
• Tomsk State University, Russia
• University of Mainz, Germany
• Moscow Kurchatovs Institute, Russia

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Research fields

• Low-pressure discharge plasma studies, mainly,
  inductive/capacitatively coupled
• High frequency electrodeless discharge lamp
  technology and manufacturing
• Plasma/wall interaction
• Working life studies
• Radiation stability
• High-resolution emission spectroscopy, time and
  spatially resolved
• Spectral line shapes (resolution approx. 0.05
  cm-1) (VUV-IR)
• Spectral line intensities - absolute and relative
  (VUV-IR) in dependence on working conditions,
  pressure etc
• Ion trap spectroscopy
• Atomic absorption spectroscopy
• Zeeman spectroscopy
• Daylight measurements
• Mercury concentration detection in the
  environment
• Theoretical studies of the Ridberg atom
  interaction with half-cycle pulses

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Atomic absorption and self-absorption method
Plasma source
Unit volume

• The light from the unit volume can be absorbed by
  the rest of the plasma source

• One can obtain the optical density by changing
  the length of the plasma source

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1. Method using a mirror
A the relative absorption Ia , Ib the
intensity of the plasma sources a and b r the
reflection coefficient of the mirror l1, l2 the
lengths of the plasma sources a and b
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2. Method using a spectral light source

• The precision of the method can be improved by
  placing the line spectra light source instead of
  the mirror.

A the relative absorption IL the intensity
of the lamp (plasma is off) IP the intensity of
the plasma (lamp is off) ILP the intensity of
the plasma and lamp

• In this experimental work the high-frequency
  electrodeless discharge lamp (HFEDL) have been
  used

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Determined concentrations for level s5 using both
methods
p 0.5 mbar, P 2.26 kW Gas flow 200 sccm Ar/
H2 mixture (Ar 10..100)

• The concentrations for the metastable level s5
  determined with two methods coincide within the
  experimental error.

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Hg/Ar low pressure inductive coupled plasmas
The intensity of the resonance line 253.7nm
versus the cold spot temperature. Dashed line
numerical calculation, points experimental
data..
N. Denisova , G.Revalde, A. Skudra, G.Zissis,
High-frequency electrodeless lamps in an
argon-mercury mixture, J.Phys.D.Appl.Phys. 38,
2005, 3275-3284.
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Electrodeless discharge lamps

• Bright radiators in the broad spectral range
  (VUV - IR)
• Filled with gas or metal vaporbuffer gas like
  Sn, Cd, Hg, Zn, Pb, As, Sb, Bi, Fe, Tl, In, Se,
  Te, Rb, Cs, I2, H2, He, Ne, Ar, Kr, Xe,
  Dy,Tu(first samples) as well as combined Hg-Cd,
  Hg-Zn, Hg-Cd-Zn, Se-Te etc (also isotope
  fillings, as example Hg202) etc.
• 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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Line shape studies
Spectral line shape measurements and modelling,
to control self-absorption and to get important
plasma parameters (such as gas temperature, lower
state density, etc)
Zeeman spectrometer
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Theoretical approach

• Observed spectral line profile
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  (1)
• where f (x) - real profile, f(x) -
  instrumental function,
• ? (x) - function characterizing random
  errors.
• 2 methods to find the real spectral line shape
• Line shape modeling non-linear multi-parameter
  fitting of the model profile to an experimental
  spectral line profile by varying unknown
  parameters
• Solving the inverse task using Tikhonovs
  regularization method

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Modelling

• Model includes the basic factors causing the
  spectral line broadening in HF discharge
  Doppler, natural, collision.. These effects are
  accounted by means of the Voigt profile.
• Multiple overlapping lines are generated
  including hyperfine splitting and isotope shifts.
  
• Self-absorption (one beam approximation)
• The resulting profile is a convolution of the
  manifold of self-absorbed profiles and the
  instrument function.
• The resulting profile is fitted to the
  experimental lines by means of a non-linear
  multi-parameter fitting procedure.
• Typically the following parameters are fitted
  atom temperature, collisional broadening, optical
  density, light source inhomogenity, width of the
  instrument function.

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Solving the inverse problem by Tikhonovs method
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Mercury 185 and 254 nm line examples in
dependence on the Tcold spot (0oC-100oC)
Modelling
Ar/Hg 202 (99.8 ) 253,7 nm line

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185 nm resonance line
Reconstructed shapes
i200 mA
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Hg 253.7 nm line intensity time dependance
Plasma/wall interaction
Working life studies
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Blackening of the walls of the vessel in the
capillary lamp
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12 nm z-range
X, Y range 3 mm
Images of the vessel surfaces obtained by AFM a)
without plasma treatment b) after plasma
treatment
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Regular daylight study 3 years experience
Relative daylight at 1200 during 2004
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Spectral changes
Daylight in the winter and summer
Wavelength, nm
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Mercury concentration detection in air in real
time with 2 ng precision
GPS

• Rigas city example

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Mercury concentration measurements in the
criminalistics
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Mercury rest in cartridge cases after the shot
Hg concentration
Time after the shot
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Thank you for attention!