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Re: [Phys-L] Infinite square well experimental data?



On 12/28/2015 07:42 AM, Daniel V. Schroeder wrote:
For many years it has bugged me that we never show students any
experimental data to compare to the calculated energy levels of a
one-dimensional infinite square well. Does anyone know of such data?
Obviously the 1-D infinite well involves many idealizations that will
hold only approximately for actual physical systems, natural or
fabricated.

OK...

But the essential result, it seems to me, is a quantum
ladder of energy levels that get farther apart as you go up.

I don't see that as truly essential; that depends on an additional
assumption, namely energy proportional to k^2. For electromagnetism
including optics, and for sound, and for other massless excitations,
the energy only goes like |k| to the first power.

Can
anyone point me to an experimental energy level diagram that has this
property?

*) I get almost 8000 hits from
https://www.google.com/search?q=%22quantum+dot%22+%22square+well%22

*) Another example is /spin waves/ aka /magnons/ in a linear or
rectangular sample. Spin waves have a parabolic dispersion
relation, i.e. energy proportional to k^2.

*) In addition: If you will settle for a non-dispersive dispersion
relation, there are lots of relevant experiments. Start with PIRA
3D30.17, 3D30.19, 3D30.20, et cetera. More generally, I get almost
40,000 hits from
https://www.google.com/search?q=%22closed+tube%22+resonance

*) Continuing down that road: Electrical analogy is current in a
piece of coax open at both ends, or voltage in a piece of coax
shorted at both ends.

You won't see published numbers on this, because observations
agree with theory so closely that nobody would be interested.
However, real-world engineers depend on this, and if the theory
were not correct I guarantee you somebody would have notices.