In the Mossbauer effect, a radioactive nucleus in the crystal lattice
emits a photon. Normally, such an emmission should be
accompanied by recoil: the nucleus jerks back causing creation of the
phonon (sound) wave propagating outside in all directions.
That's not what happens in rare cases when the Mossbauer effect
works. In these cases, the emitted photon gets coupled to the
so-called "zero-phonon" vibrational mode of the crystal. This is
simply the mode in which all atoms in the crystal move together
in one direction. No lattice vibrations (phonons) are created.
In these cases the recoil momentum is spread evenly (and
instantaneously) between all atoms in the crystal lattice.
Again. Nothing is spread instantaneously. The recoil momentum could
be distributed among all the atoms very fast, but never
instantaneously.
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.
Do you have a reference?
No, I haven's found any discussions of this idea. That's why I am
asking you.
