The Mossbauer Effect

The Mossbauer Effect is the physics foundation of the experiment considered here.  The Mossbauer Effect is significant in that it allows for high sensitivity measurements of energy deviations on the order of one part in 10^13.  Before a discussion of the experiment begins, it is important to understand what the Mossbauer Effect is.  

First consider resonance radiation.   Resonance radiation occurs when radiation from an 'emitter', a source emitting radiation through transition from state a to state b , is incident on an 'absorber' in state a, that will in turn be excited into state b by the incident radiation.   What about conservation of Energy??  Resonance radiation is not as ideal as it sounds.  When a nucleus emits a photon, it will recoil with some momentum in compliance with conservation laws.  Conservation of energy then gives us that the energy coming from the emitter must be equal to the transition radiation minus the recoil energy.  The absorber is also regulated by conservation laws.  It will have a recoil energy of it's own, and to transition to the final state it must have the full transition energy, no longer given by the emitter when you take into recoil energy into account.  

What happens if you have a very small Recoil Energy?  This is the question that Mossbauer asked.  If there was a way to have Resonance radiation with a very small recoil energy, therefore a very small linewidth...extremely sensitive measurements in energy differences would be possible.  Absorption of resonance would be confined to the strict criteria mentioned above...the energy spread would be tiny.  Measurements of small energy fluctuations would be possible.  

Mossbauer recognized that a crystal lattice can be excited with excitations called phonons.  Phonons have a given momentum and Energy with a minimum energy given by E=(Boltzman constant)(Debye Temperature).    (For more information about phonons CLICK HERE )  A phonon will not occur when the recoil energy (as determined by a free particle) is less than the minimum energy given above.  When this happens a gamma ray is emitted with an essentially recoiless emission.  

                                    THE EXPERIMENT

This experiment will measure the energy splitting of the 14.4keV state of Fe57 from the hyperfine structure effect.  Hyperfine structure is a direct result of the Zeeman Effect.  These are very small energy differences that were only speculated to exist in certain materials.  The Mossbauer effect enabled the measurement of these structures, and will enable you to measure them as well.  

In this experiment a Cobalt 57 source decays via electron capture into Fe57...resulting in a source dubbed FeCo.  FeCo is Ferromagnetic and is not sensitive to hyperfine splitting.  FeCo is used as the emitter in this experiment.  The absorber will vary.  You will test steel, nothing and Fe57.  The interesting result is what you see when you use Fe57 as the absorber.  Standing still, Fe57 will not absorb the 14.4keV energy from FeCo.  But if you create tiny shifts in energy, Fe57 will absorb from the FeCo source....as the tiny shifts in energies reach the levels of the hyperfine splitting.  

The energy shifts are provided by the Doppler shift .  Your Absorber will be attached to a moving device connected to a Constant Acceleration Drive that moves between 7mm/s and -7mm/s.  The Doppler shifted energy is small, and you will see absorption at 6 points within the 7mm/s to -7 mm/s range.  These peaks correspond to the split levels.  You will be able to determine B field, magnetic moment from these peaks...If you need help...ask Rob Jorstad .  I did!  Anyhow, you will want to keep in mind selection rules for these type of processes.  ( Selection Rules )

Links directly related to this Experiment:  (there is a wealth of knowledge out there regarding this/and variations of this experiment)

Interesting Links:

Non-Interesting Links:

THE BEST LINK DIRECTLY RELATED TO THIS EXPERIMENT IS:

THIS LINK