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Line Spectrum of Mixtures

  1. Oct 29, 2005 #1
    I understand that there are atomic spectra for the elements, but how do you predict the line spectrum of a mixture of 2 elements like a H-He mixture? Must you combine the lines from both elements?
  2. jcsd
  3. Oct 29, 2005 #2
    Are you talking about something like fluorescence spectroscopy?
    If I understood what you're asking correct I think one should get the the emission lines of the invidual elements and the intensities of the peaks tell you the relative compositions.
  4. Oct 30, 2005 #3
    That wolud be only in the case that there aren´t any interactions between both of the species in the mixture. Probably the energy levels of the species would became shifted by the presence of each other.

    There also can be energy transfers between different states of the species. That would lead to new lines of absorption or emmision. Although I can´t tell you nothing about the case you´re talking about (H, He).
    Preparation and study of atomic H is not easy. Interactions between them would depend on the conditions of the experiment: method of preparation of atomic H, pressure and expansion dynamics (rate of collisions), composition of the mixture.
  5. Oct 30, 2005 #4
    The activity that will be done in class is similar to this one, except different elements will be used and a computer program:
    But one of the prediction questions with the H-He is the same (#5).
    I hope these examples might make my inquiry crystal-clear.
    Also, I'm a bit lost on your explanations with the peaks since I'm a beginner. :blushing:
    Last edited by a moderator: Apr 21, 2017
  6. Oct 30, 2005 #5


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    altered-gravity : There's no atomic H in this situation.

    Soaring crane : You should have said the mixture was H2-He. The interaction between molecules here is really small and can be neglected to first order. A mixture of two species will show (under these conditions) the spectral lines of both species. Are you able to answer Q3 in this lab ? Unless you can, the lab is essentially pointless.
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