Harmonics

[swansont]

What I was getting at was that I probably either misheard him or misinterpreted what he said. He could have just said that more transitions than 1-2' date=' 2-3, 4-3, etc are possible. To be honest, it was so long ago that I can't remember exactly what was said.

 

Can you explain more in depth the rules with 2 photons, and the situatations under which these are valid? And what's the weak nuclear interatction mixing the 2s and 2p states? I know what 2s and 2p are, just what's the weak nuclear interaction? Is it just the weak force (like the strong force, but the weak force; not just a weak force... You get the idea)?[/quote']

 

If you get 2 photons interacting at essentially the same time, it's possible for their combined energy to cause an excitation (and also to get a photon of the combined energy to be emitted) Since each carries 1 unit of angular momentum, they can add to zero, or to two units. So you get different excitations than for a single photon.

 

The weak interaction is indeed the weak nuclear force, which is really the electroweak interaction. The 1S-2S transition in Hydrogen is one that has been studied to learn about parity nonconservation (PNC), which can happen when the weak force gets involved (and also any of the ground state S levels with the first excited S state for the hydrogen-like alkali atoms). IIRC it's because in the s-states, the electron spends part of it's time within the nuclear radius, so there is a small shift in the energy, and there is coupling between the 2S and 2P states.

[calbiterol]

Now look at the hydrogen atom. In first approximation its energy levels are given by:

 

[math]E_n=\frac{-13.6eV}{n^2}[/math]

 

How did you get this? I see the value in the CRC Handbook of Chemistry and Physics under x-ray atomic energy levels for hydrogen' date=' and it is approximately equal to 13.6. Is this a coincidence, or is this the figure? Will this apply to all elements? Also, where does the negative come from?

 

Alternatively, would nitrogen's approximation be given by [math']E_n=\frac{-401.6eV}{n^2}[/math]?

[swansont]

The hydrogen energy levels can be derived by quantizing the angular momentum and assuming circular orbits, and recognizing that the energy is sum of the kinetic energy and electrostatic potential energy (which is negative). This is the Bohr model, and while it's physically wrong, it does predict hydrogen-like levels properly. But once you add other electrons and their interactions, you're out of luck (unless you can find ways of simplifying those effects, like the screening of a filled shell for alkali atoms)

 

Or you can solve the Schroedinger equation for hydrogen.

[calbiterol]

What is the Schroedinger equation?