Re: Mossbauer effect and retarded interactions

Eugene Stefanovich wrote:

> If the recoil wave propagates in the crystal with a finite speed
> (e.g., the speed of light), then atoms closer to the emitting nucleus
> would shift earlier than the atoms further away. This means that
> some phonons are created. But there are no phonons in the Mossbauer
> effect. The entire crystal recoils as a whole.

Phonon number is a good quantum number only for stationary states of an
isolated crystal. The transition from one stationary crystal state
(before gamma emission) to another stationary crystal state (after
gamma emission) takes place over an unspecified amount of time. In
fact, this time is taken to be long enough for the nucleus + crystal
system to settle into a state that is well approximated by a tensor
product of stationary states of its constituents.
In other words, gamma emission is not an instantaneous event, but takes
certain amount of time. This time must be sufficient to propagate the
recoil to the whole (or at least a large part of the) crystal.

> > Do you have a reference?
>
> No, I haven's found any discussions of this idea. That's why I am
> asking you.

And the answer is no, the recoil does not happen instantaneously.

Igor

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