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[Phys-l] photoelectric effect & photon emission

I have a question regarding photon emission & quantum states.
When an electron absorbs energy and gets excited, when it transitions to a new /n/, does it actually exist in between these n values? Does it dis-appear while it is inbetween these n values? Does the wave function describing it simply change, so it doesn't end up with any trouble existing in between n=1 & n=2 (where it should Not be in terms of probabilities)?

I have this same question for when the excited electron 'falls' from n=2 to n=1. I understand that the energy is released by screaming out a photon. I do not quite get if the falling electron exists in some 1<n<2 state, if the wave function describing the electron has changed to cover for this, or what.

Thanks for any insight.

Paul Lulai
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From: on behalf of John Denker
Sent: Sun 4/27/2008 3:18 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] fermi energy and electrostatic potential

On 04/27/2008 12:41 PM, wrote:
I am having trouble with a "gut understanding" of why the fermi level
is constant across a junction between two materials.? It seems to
trump the electrostatic potential.

You need to account for the protons. There is a tradeoff
involving electron KE, electron-electron electrostatics,
and electron-proton electrostatics. Total energy "trumps"
electrostatic energy. Typically there is a higher density
of unshielded protons (in the form of ion cores) on one side
of the junction relative to the other. Also a higher KE on
one side relative to the other.

The KE terms in the equation of motion are often given too
little attention. Keep in mind the potential energy terms
are non-directional, in the sense of being spherically
symmetrical. All of the directionality we see in chemical
bonds (especially in organic molecules) comes from the
directionality of the _KE_ terms.

I have a mental picture of electrostatic potential as the surface of
water and if two containers filled with water are joined, perhaps by
a tube, water will move from one container to the other until the two
surfaces are at the same height.? Can I add a feature to this mental
picture to include fermi energy?

Let one arm of a U-tube be inside a capacitor. Charge up
the capacitor. The water will rise higher in that arm,
because water is a dielectric. Total energy "trumps"
gravitational potential energy.

Forum for Physics Educators