Is 3s to 2s transition for Hygrogen forbidden?

[SimonZ]

For hydrogen emission spectra from n = 3 to n = 2:


My question is: In the following transition which is (are) possible or impossible and why?

3s --> 2s, 3s --> 2p
3p --> 2s, 3p --> 2p,
3d --> 2s, 3d --> 2p,

 

[TMFKAN64]

Selection rules! If you have a copy of Griffiths' "Introduction to Quantum Mechanics", take a look at section 9.3.3.

 

[Nabeshin]

You need to have \Delta l = \pm 1 for any transition.

 

[ytuab]

The number of observed hydrogen spectrum lines is much fewer than theoretically expected.

Atomic physics by Max Born
In page 167, it is written as follows,

-------------------------------------------------------------------------
The case of hydrogen is peculiar in one respect. Experiment gives distinctly fewer terms than are specified in the term scheme of fig 9; for n=2 only two terms are found, for n=3 only three, and so on.
The theoretical calculation shows that here (by a mathematical coincidense, so to speak) two terms sometimes coincide, the reason beeing that the relativity and spin corrections partly compensate each other.

It is found that terms with the same inner quantum number j but different azimuthal quantum numbers l always strictly coincide.
----------------------------------------------------------
http://books.google.com/books?id=NmM-KujxMtoC&printsec=frontcover&dq=Max+Born&lr=

Hydrogen atom has only one electron. So is it relevant?

To search spectrum line, please see http://physics.nist.gov/PhysRefData/ASD/lines_form.html
and enter "H" into "Spectrum" part. "Observed wavelength" is observed line, and "Configurations" is theoretically permitted transition.

Even if we consider selection rules(due to spin 1 of photon), the observed spectrum lines are fewer than expected.

 

[Bob_for_short]

You need to have \Delta l = \pm 1 for any transition.

It is valid for one-photon transition. For many-photon transitions this is not true. Such processes occur, just with much smaller probability.

 

[Nabeshin]

It is valid for one-photon transition. For many-photon transitions this is not true. Such processes occur, just with much smaller probability.

Thank you for the correction :)

 

[Pythagorean]

Also, aren't selection rules broken by relativistic corrections?

I have a friend who's really into super conductors and he's showed me before where selection rules and gauge symmetry get broken up. Most of the experiments comes form the ESA:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVJ-4H57JRK-2&_user=6861066&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=960704834&_rerunOrigin=google&_acct=C000055858&_version=1&_urlVersion=0&_userid=6861066&md5=9454a1fb6b2b2da44f5ff095d6b70ccc

 

[PiratePhysicist]

The selection rules are not "broken" so much as supplemented when you introduce the corrections. For example, when you introduce fine and hyperfine structure corrections, you get more selection rules.

One thing to note about selection rules, what you are calling "selection rules" are "selection rules for a electric dipole transition", you can have higher order electric transitions and you can have magnetic transitions, which will follow different rules. Magnetic dipole, quadrupole, etc and electric quadrupole, etc transitions are orders of magnitude less likely to occur, and so are often ignored. So cases where you see them broken, they may just not be electric dipole transitions.