Energy and momentum transfer to the lattice

The vibrational energy of the lattice as a whole can only change by discrete amounts 0, ho, etc. If ho) then either zero or tim units of 

Mossbauer y-ray energies (Ey) Chemical binding and lattice energies Fiee-atom recoil energies (Eg) 

Lattice vibration phonon energies Heisenberg natural linewidths (C,) 

It is important to emphasise that y-ray energies cannot be measured with this accuracy on an absolute scale indeed these energies are seldom known to better than 1 part in 10. In order to use the precision of the Heisenberg width, it is customary to use as a reference a radioactive source in which all the emitting atoms have an identical chemical environment. This is then compared to an absorbing chemical matrix of the same element and only the minute difference between the two transition energies is measured. The means whereby this is accomplished will be discussed shortly. 

The third of these possibilities is eliminated by the high chemical binding energy and the fourth has been shown to be minute because of the large mass 

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