The Mssbauer effect was discovered using the decay of the 0.12939 MeV second excited state of 191

The Mössbauer effect was discovered using the decay of the 0.12939 MeV second excited state of ¹⁹¹Ir. The lifetime of this isomer is 0.13 ns.

(a) Compute the width Г of this level.

(b) Compute the recoil energy of a free ¹⁹¹Ir atom that emits the 0.12939 MeV photon.

(c) Resonant (recoilless) absorption occurs when ¹⁹¹Ir is bound into a lattice. If a Doppler shift equal to Г destroys the resonance absorption, show that the Doppler velocity v necessary is given by

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