Partial Mossbauer effect—Why not?

[jimgraber]

A photon can be absorbed by a crystal. The recoil is absorbed by either a single atom (ordinary absorption) or by the entire crystal (Mossbauer effect) Why do we not observe absorption by two or three atoms at the small end or by one half or one third of the crystal at the high end?
TIA.
Jim Graber

 

[genneth]

Gamma radiation involves kicking out a photon, so by conservation of momentum some momentum has to be imparted to the thing that emitted it. However, in a crystal, momentum can be absorbed into lattice vibrations as phonons. The latter are quantised in energy and momentum, so there is a possibility of no phonons being excited. If you were to manage to excite one or two phonons I guess that would correspond to your case of partial Mossbauer effect? The only problem is that phonons carry *much* more momentum than photons, so even one or two may cause sufficient broadening for the effect to be described as effectively having disappeared.