A free sationary `Ir^(191)` nucleus with excitation energy `E=129 keV` passes to the ground state, emitting a gamma quantum. Calculate the fractional change of gamma quanta energy due to recoil of the nucleus.

Explanation

With recoil neglected, the `gamma` quantum will have `129keV` enrgy. To a first approximation, its momenturm will be `129keV//c` and the energy of recoil will be
`((0.129)^(2))/(2xx191xx931)MeV= 4.18xx10^(-8)MeV`
In the next approximation we therefore write `E_(gamma)overset~-.129-8.2xx10^(-8)MeV`
Therefore `(deltaE)/(E_(gamma))=3.63xx10^(-7)`