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THE MÖSSBAUER EFFECT

Ram Avinery  
Instructor of the Mossbauer experiment

 

Room: Nano Center 35

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Contents:

  1. Introduction
  2. Topics of the experiment
  3. How to prepare for the experiment?
  4. The experimental schedule
  5. Literature
  6. Links

 

Introduction:

Nuclear physicists have a strong and understandable tendency to ignore the chemical binding of the atoms whose nuclei they investigate. This is based on the fundamentally sound perception that the energies involved in nuclear reactions are so much larger than the energies of chemical binding that the atom may well be thought of as a free atom when analyzing nuclear events. Conversely, nuclear properties, such as the mass and the ground-state moments, are of little interest to chemists or solid-state physicists.


 

Occasionally discoveries are made which bridge between these disciplines and make contributions in both fields - Perturbed angular correlations and positron annihilation in solids fall into this category. A case of particular interest is the recoil- free emission and resonant absorption of nuclear gamma rays in solids, which were discovered by Rudolf L. Mossbauer during his graduate work at Heidelberg in 1957. 

In 1958 Mossbauer published his PhD thesis discovery that a small fraction of nuclei held in a solid crystalline structure exhibit sharp-line absorption and emission spectra characteristic of no recoil. The spectral line widths have almost exactly the value predicted from the lifetimes of the states, rather than the much larger widths characteristic of when the nuclei can recoil individually. It's as if the entire massive solid structure of the crystal recoils, rather than an individual nucleus. The nuclei are strongly coupled to the crystal structure, rather than simply being locally constrained. In the case of the 14.4 KeV transition of Fe57, the resolution (line energy)/(line width) is the order of 1ªe10, a resolution only attainable by atomic beams, hydrogen masers, or trapped ions. This transition can therefore be used as an exceedingly sharp probe to investigate internal crystalline fields, and magnetic dipole and electric quadruple moments of nuclei. It has also been used to detect gravitational red shifts in the laboratory. 

Doing the experiment is a good way to learn about nuclear physics, energy levels and radiation, and condensed matterphysics.
 

 

Topics of the experiment:

  • Emission of Gamma Rays by Nuclei, Resonant absorption, Mossbauer Effect.
  • Interaction of charged particles and photons with matter.
  • Techniques and equipment used in Nuclear Physics experiments.
  • Use of the Mossbauer Effect in the study of hyperfine structure.
  • Measurement of the internal fields in various different materials.

 

How to prepare for the experiment?

  1. Read the relevant literature: 
    1. Mossbauer spectroscopy / N.N. Greenwood , T.C. Gibb : 1st chapter, 2nd chapter, 3rd chapter.
    2. Principles of Mossbauer Spectroscopy / T. C. Gibb
    3. Melissions: Experiments in modern physics
    4. The Mossbauer experiment instructions
  2. Study the experimental equipment
    1. Scintillation detectors. 
    2. Multiple channel analyzer / Single channel analyzer
    3. Pre-Amplifier and Amplifier.
    4. Function Generator.
    5. Motor and Controller.
    6. Photomultiplier and High voltage power supply.
  1. Learn the experiment's schedule.
  2. Make sure yourself that you understand the experimental technique.
  3. Answer the preparation questions. (in the experiment's instructions)
  4. Learn the safety rules to work with radioactive materials.

 

 

The experimental schedule:

  1. Written exam - Approximately one hour.
  2. Learning the experimental apparatus. Configuration of the MCA program.
  3. Learning the analyzing programs.
  4. Setting the energy window.
  5. Measurement of Fe57 energy spectrum patterns.
  6. Measurement of Fe57 absorption spectrum for different absorbers.
  7. Calibration of the velocity scale.

 

Literature:

1.  Mossbauer spectroscopy / N.N. Greenwood , T.C. Gibb (1, 2.1, 2.3, 2.7, 3-3.7)

2.  Principles of Mossbauer Spectroscopy / T. C. Gibb

3.  Melissions: Experiments in modern physics

4.  C. E. Violet, D. N. Pipkorn: J. Applied Physics Volume 42, Issue 11, pp. 4339-4342

5.  D.C. Kistner, A.W. Sunyer: Phys. Rev. Lett. 4, 22a (1960).

6.  The Mossbauer experiment at Harvard University

7.  Detectors & Instruments for Nuclear Spectroscopy / EG&G ORTEC 

8.  Table of Isotopes

 

 

Links:

  1. MIX - Topics related to Mossbauer spectroscopy
  2. CHP - Mossbauer Spectroscopy 
  3. Taking a Mossbauer Measurement 
  4. Cosmic Rays: Scintillators and Phototubes 
  5. MINOS Scintillator Images 
  6. Scintillator Counters 
  7. Scintillator X-ray Detectors 
  8. Mossbauer Effect Reference Database

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