Energy levels of helium/equation

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Discussion Overview

The discussion revolves around the energy levels of helium and helium-like atoms, particularly in relation to the energy levels of hydrogen-like atoms. Participants explore the complexity of deriving equations that fit the observed spectrum of helium and the methods used to obtain these energy levels.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant presents the equation for energy levels of hydrogen-like atoms and questions the corresponding equation for helium or helium-like atoms, suggesting that helium's spectrum may resemble two hydrogen spectra superimposed.
  • Another participant asserts that exact solutions for helium-like systems are not possible, indicating that only two-body systems can be solved exactly.
  • A participant clarifies that they are not seeking a solution but rather an equation that fits the empirically observed spectrum.
  • There is a contention regarding the definition of a solution, with one participant suggesting that fitting an experimental spectrum might involve complex mathematical constructs, which could be impractical.
  • Another participant mentions that in practice, researchers typically refer to tables or charts for energy levels or utilize computer simulations, referencing the work of Gordon W. F. Drake for accurate calculations of helium.
  • It is noted that understanding Drake's calculations requires advanced knowledge of quantum mechanics.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of deriving an equation for helium's energy levels, with some suggesting that empirical fitting methods may not be practical. The discussion remains unresolved regarding the specific equations or models that could be used.

Contextual Notes

Limitations include the complexity of helium's energy levels compared to hydrogen-like atoms and the potential impracticality of fitting experimental spectra with simple equations.

granpa
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the equation for the energy levels of a hydrogen-like atom is:

e1fff0de782fe5dfb583088b40a82165.png


Note that aμ, is approximately equal to a0, (the Bohr radius). If the mass of the nucleus is infinite then μ = me, and aμ = a0

b17195a99c8dbe999ce3f8bc86a6e03a.png


but what is the equation for the energy levels of a helium or helium-like atom? I've heard that heliums spectrum is simply 2 hydrogen spectrums superimposed so it should be quite simple.
 
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as far as I know, you can't solve those system exactly. Only two-body systems can be
 
I'm not asking for a 'solution'. I'm asking what equation fits the empirically observed spectrum.
 
But that's what a solution is.
 
I'm not even going to touch that.
 
So what ARE you asking for then?
Are you asking if there is e.g. an interpolating polynomial (or more realistically; an expansion using some other bases; e.g. Lorentzians) that fits the shape of an experimental spectrum?

I doubt such a thing exist; it is of course possible to create but it would need to contain so many terms that it would be useless; it is much easier to look up the data in a table or just run a computer simulation.
 
In practice, as far as I know, people either look up the energy levels from a table or chart, OR they run computer simulations to calculate them.

For the simulations, you might do a search on Gordon W. F. Drake. He practically made a living from accurate calculations of helium, at least in the 1990's. Three references to his work are given here:

http://physics.nist.gov/PhysRefData/Handbook/Tables/heliumtable7.htm

EDIT: Understanding Drake's calculations in any detail pretty much requires grad-school level quantum mechanics.
 
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thank you. that was extremely helpful.
 

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