380 7 Nuclear Physics – I
Nuclear resonance fluorescence
IfE 0 is the transition energy in an atom of massM, the resonance energyEγ=hν
is given by
Eγ=E 0 −E^2 γ/ 2 Mc^2 (7.52)The recoil energy
ER=E^2 γ/ 2 Mc^2 (7.53)The width of the energy levelΓis the full width at half maximum, Fig. 7.10.Γis
calculated from the mean life time by the uncertainty principle
Γ.τ= (7.54)Fig. 7.10Nuclear resonance
fluorescence
Compensation for the recoil energy loss
Source velocityv=E 0 /Mc (7.55)Mosbauer Effectis the recoilless emission and absorption of nuclear radiation
ΔEr/Er=v/c. (7.56)Radioactivity
Radioactivity is the spontaneous disintegration of an atomic nucleus. In natural
radioactivity, the decay may occur via alpha, beta or gamma emission. In artificial
radioactivity, neutron or proton may also be emitted.