Calibrating Argon Spectrum with MicroLab Spectrometer Model 141

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Discussion Overview

The discussion revolves around methods for calibrating the argon spectrum using a MicroLab Spectrometer Model 141. Participants explore alternative reference sources for spectral calibration in the absence of a gas discharge tube, focusing on chemical substances and other light sources that exhibit known absorption or emission wavelengths.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Jagadeesh seeks suggestions for chemicals that absorb or transmit light in the visible range (400 to 700 nm) for spectral calibration, mentioning chlorophyll as a potential option.
  • One participant suggests that gas discharge tubes are inexpensive and effective for calibration, while also noting that optical filters can provide narrow transmission or absorption windows.
  • Another participant reiterates the affordability of gas discharge tubes and suggests that they could be used at home after purchase.
  • A different participant proposes using xenon lamps, which have a sharp emission peak at 467 nm, and mentions lanthanide salts, specifically terbium and europium, which emit at specific wavelengths when excited with UV light.
  • Jagadeesh expresses uncertainty about the availability of lanthanide salts locally and considers fluorescent lamps, which have known emission lines from mercury and europium.
  • Participants note that fluorescent lamps also exhibit lines from mercury, indicating their potential as a reference source.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best calibration method, with multiple competing views on the use of gas discharge tubes, lanthanide salts, and fluorescent lamps remaining present throughout the discussion.

Contextual Notes

Participants mention budget constraints affecting the ability to procure certain equipment, which may limit the options available for calibration. There is also uncertainty regarding the local availability of suggested chemicals.

Who May Find This Useful

This discussion may be useful for individuals interested in spectroscopy, calibration methods, and alternative light sources for spectral analysis, particularly in educational or budget-constrained settings.

jagadeeshr
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Hi,

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.
http://www1.biologie.uni-hamburg.de/b-online/e24/3.htm

Thank you
Jagadeesh
 
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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.
 
mfb said:
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.

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.
 
A few dollars looks quite cheap, and you might be able to use it at home afterwards if you buy it yourself.
 
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.
 
Fluorescent lamps also show the lines of mercury.
 
Well of course, they are low vapor mercury lamp.