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Spectrum Calibration

  1. Feb 20, 2017 #1

    I need some help to calibrate argon spectrum.

    I have a MicroLab Spectrometer (Model 141) to obtain spectral images of argon plasma. To calibrate the spectral images, I need a reference of known wavelength.

    Usually, a discharge tube is used to obtain the reference spectrum. However, I cannot procure it now due to budget issues.

    Another method is to is to fill a vial with chemical of known absorption/transmittance wavelength, and place it in the spectrometer. The wavelength at which the liquid absorbs or transmits light can be used as a references to calibrate the unknown spectrum.

    Can you suggest any chemical that absorbs or transmits light in the visible range (400 to 700 nm)?

    I could only think of chlorophyll. Maximum absorption at 430 & 662 nm for chlorophyll a and 453 & 642 nm for cholorophyll b.

    Thank you
    Last edited: Feb 20, 2017
  2. jcsd
  3. Feb 20, 2017 #2


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    You can get gas discharge tubes for a few dollars. I don't know your budget, but it will be hard to get anything cheaper than that. Better ones cost more, but that is always the case.

    Optical filters can have very narrow transmission or absorption windows. Sodium, rubidium, ... in flames produce narrow lines.
  4. Feb 20, 2017 #3
    Thanks for the reply. The project budget will be approved in March, until then no "official" purchases can be made. So, I was looking for cheap alternatives.
  5. Feb 20, 2017 #4


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    A few dollars looks quite cheap, and you might be able to use it at home afterwards if you buy it yourself.
  6. Feb 20, 2017 #5


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    How about Xe lamps? They have a sharp emission peak at 467 nm.

    If you are looking for chemicals, try known lanthanides salts. Excite it with UV (around 375 nm) and most of the time you will see their emission. Terbium or Europium salts show sharp emission peak at around 545 nm and 612 nm, respectively. Terbium is a little bit costly, but Europium nitrate cost around $60 per gram.

    I have Europium nitrate at hand. If you want, I can give you the spectrum.

    Better yet, you can also try Fluorescent lamps. They contain Eu3+ doped Y2O3 that emits in 610 nm or something.
  7. Feb 21, 2017 #6
  8. Feb 21, 2017 #7


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    Fluorescent lamps also show the lines of mercury.
  9. Feb 21, 2017 #8


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    Well of course, they are low vapor mercury lamp.
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