Relative intensity changing with temperature?

[AdrianH]

I am trying to determine the temperature in a discharge lamp. I have the spectrum of that lamp and Nist Atomic Spectra Database. I don't have the pressure in the lamp (can I determine that too? How?). The spectrum that I have has a low resolution (of about 0.3 nm). Can this be done?
1) One method that I know is to compare 2 distinct lines that represent the transitions from one energy level to two fairly different energy levels or transitions from two different levels to a single level (am I wrong?).
2) Checking the broadening and the self-absorbtion of a line (assuming that the pressure is sufficient), but I don't know much about this. Can someone explain this technique or point me to the literature (would the resolution be enough for this?)

(sorry for my english, I'm romanian)

 

[Andy Resnick]

The problem is that discharge lamps don't have a blackbody spectrum (or even a close approximation), so determining a thermodynamic temperature is problematic.

There are numerous ways to assign a temperature based on the relationship between your lamp output and that of a blackbody radiator (effective temperature, etc.)

The broading of the line could probably give you a pressure measurement- look up "homogeneous line broadening", but I would be surprised if the number was significantly different than the manufacturer spec.

 

[astrokreng]

I can provide some insights on your query. The relative intensity of a spectrum can indeed change with temperature, as temperature affects the energy levels of atoms and molecules, leading to changes in their emission and absorption spectra. In order to determine the temperature in a discharge lamp, you can use the Nist Atomic Spectra Database to compare the observed spectrum with known spectra at different temperatures. This can help you identify the temperature at which the observed spectrum matches with the known spectrum.

To determine the pressure in the lamp, you can use the broadening and self-absorption techniques. Broadening refers to the widening of spectral lines due to collisions between atoms or molecules at different pressures. Self-absorption, on the other hand, occurs when the atoms or molecules in the lamp absorb the radiation they emit, leading to a decrease in the intensity of the spectral lines. By analyzing the broadening and self-absorption of the spectral lines, you can estimate the pressure in the lamp.

The resolution of 0.3 nm may not be sufficient for accurate analysis of broadening and self-absorption effects. You may need a higher resolution spectrum to accurately determine the pressure in the lamp. As for comparing two distinct lines, it can be a useful method to estimate the temperature, but it may not be as accurate as using the Nist Atomic Spectra Database.

I hope this helps answer your questions and provides some guidance for your research. If you need more specific information, I would suggest consulting relevant literature on atomic and molecular spectroscopy. Best of luck with your research!