Re: Temperature and radiation absorption
From: Paul Draper (pdraper_at_yahoo.com)
Date: 09/24/04
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Date: 24 Sep 2004 05:44:17 -0700
billybilly54321@hotmail-dot-com.no-spam.invalid (Doodedski) wrote in message news:<4153c433$1_2@127.0.0.1>...
>
> Second, can anyone explain to me how an atom can absorb a photon? It
> seems to me that if an electron absorbs a photon, it goes to a higher
> level of energy but must come right back down reemiting a photon? No
> additionnal energy is acquired by the atom. By which process is it
> possible for an atom (alone, in a cristal structure, in a gas...) to
> absorb a photon's energy and to keep it in the form of vibrational
> energy, kinetic energy... Oh, and what happens if the photon hits the
> nucleus?
> Thanks
The atom does re-emit but not necessarily the same photon at the same
energy. There are lots of ways for an excited atom in a lattice to
relax, because there are alternate coupling paths. A phonon released
to the lattice, for example. An atom in a molecule can also relax by
releasing energy to the bond states or to a vibrational state. The
photon can pass by a nucleus, but a low energy photon has a low
cross-section for absorption by the nucleus and so in most cases
wanders right on by.
PD
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