Can You Predict the Line Spectrum of a Mixture of Two Elements?

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Discussion Overview

The discussion revolves around predicting the line spectrum of a mixture of two elements, specifically hydrogen and helium. Participants explore the implications of combining atomic spectra, the effects of interactions between species in the mixture, and the conditions under which these predictions hold true. The context includes theoretical considerations and practical applications in spectroscopy.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Homework-related

Main Points Raised

  • One participant questions whether the line spectrum of a mixture can be predicted by simply combining the lines from both elements.
  • Another participant suggests that fluorescence spectroscopy might be relevant and notes that the emission lines of individual elements can indicate relative compositions based on peak intensities.
  • A different participant raises the possibility that interactions between the species could shift energy levels, potentially leading to new absorption or emission lines, and emphasizes the complexity of preparing atomic hydrogen.
  • One participant mentions a class activity related to the topic and expresses confusion about the explanations provided, indicating a need for clearer examples.
  • A later reply clarifies that the mixture should be considered as H2 and He, arguing that interactions between molecules are negligible and that the spectral lines of both species will be observable under these conditions.

Areas of Agreement / Disagreement

Participants express differing views on the effects of interactions in the mixture and the nature of the spectral lines produced. There is no consensus on how to predict the line spectrum accurately, and the discussion remains unresolved regarding the specific conditions and implications of the mixture.

Contextual Notes

Participants note that the interactions between species depend on various experimental conditions, such as the method of preparation, pressure, and dynamics of the mixture. These factors introduce complexity that is not fully resolved in the discussion.

Who May Find This Useful

This discussion may be of interest to students and researchers in spectroscopy, atomic physics, and those exploring the behavior of mixtures in experimental settings.

Soaring Crane
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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?
Thanks.
 
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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.
 
Hello,
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.
 
The activity that will be done in class is similar to this one, except different elements will be used and a computer program:
http://www.smgaels.org/physics/home/lab/lab4/Spectral_Lines_Lab3.htm
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:
 
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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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