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Topic: width of absorption lines  (Read 1810 times)

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Offline nigel433

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width of absorption lines
« on: October 24, 2010, 03:10:03 PM »
We are told that the absorption of EM radiation by an atom, resulting
in an electron jumping from one state to another, is very precise and
exact - in terms of the energy absorbed, and the frequency "deleted".

My question is HOW precise? If the phrase "exact energy match" is taken
literally then there will never be ANY noticeable energy taken out (for the
same reasoning as in mathematics, which implies that a precisely define
line has no width at all and therefore contributes ZERO area in an integration).

In other words "lines" in the absorption spectrum will be too narrow to see.
But of course actual absorption spectra do show up.

How come?

Offline Borek

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Re: width of absorption lines
« Reply #1 on: October 24, 2010, 04:30:20 PM »
Heisenberg and Doppler.
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Offline nigel433

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Re: width of absorption lines
« Reply #2 on: October 25, 2010, 09:12:55 AM »
ok :

- so the "Heisenberg" answer is that the energy jump is NOT completely sharp.

- "Doppler" seems to refer to shifts of observed spectra; not what I was considering,
   however.

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