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I had to analyze the emission spectrum of a compact fluorescent lamp and find what elements are present in the lamp, based on the spectrum of spikes in wavelengths. Knowing that in our lamp there was mercury, why aren't all the spikes that are characteristic of mercury showing up in our spectrum and how can we know for sure that certain spikes are attributable to certain elements knowing there are so many possibilities?

Here is our spectrum if it helps : Emission spectrum of compact fluorescent lamp

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the emission lines you detect are only those that make it all the way through the phosphor coating on the inside of the CFL tube. Those phosphors are designed to absorb as much of the spectral output of the ionized mercury as possible and convert it into a mixture of red, green and blue light that your eye interprets as "white". Based on this it isn't surprising that you don't detect all the lines.

It may also be that in your case, the current flowing through the tube is not sufficient to excite all the lines that are possible.

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  • $\begingroup$ (+1) Yep! And my echellogram (2D spectrum) of my compact fluorescent lamp is shown here: astronomy.stackexchange.com/a/49116/45954. $\endgroup$
    – Ed V
    Commented Mar 27 at 23:11
  • $\begingroup$ And the glass would have a transmission response as well. $\endgroup$
    – Jon Custer
    Commented Mar 28 at 0:27

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