Rudolf Mössbauer discovered in 1957 that transitions from an excited nuclear state occur with negligible nuclear recoil when the nucleus is embedded in a large crystal lattice because the entire lattice absorbs the recoil. A transition like that in 191Ir from the 129- keV excited state to the ground state has a lifetime of 1.9 x 10-10 s. (a) Determine the energy width of the decay. (b) Similarly, if the photon is absorbed by 191Ir embedded in a crystal, the recoil is negligible. However, even a slight motion of the absorber will lead to a Doppler shift suffi cient to destroy the resonance absorption. Calculate the speed necessary to shift the energy absorption by 5Γ, where Γ is the nuclear decay width. This effect is called the Mössbauer effect

Rudolf Mössbauer discovered in 1957 that transitions from an excited nuclear state occur with negligible nuclear recoil when the nucleus is embedded in a large crystal lattice because the entire lattice absorbs the recoil. A transition like that in 191Ir from the 129- keV excited state to the ground state has a lifetime of 1.9 x 10-10 s. (a) Determine the energy width of the decay. (b) Similarly, if the photon is absorbed by 191Ir embedded in a crystal, the recoil is negligible. However, even a slight motion of the absorber will lead to a Doppler shift suffi cient to destroy the resonance absorption. Calculate the speed necessary to shift the energy absorption by 5Γ, where Γ is the nuclear decay width. This effect is called the Mössbauer effect