Lab D4: The Mossbauer Effect

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In this experiment you can observe the Mossbauer effect, a very accurate (one part in 1017!) measurement of the energy of a nuclear gamma ray. This measurement is carried out by using motion of the source to sweep the gamma-ray energy via the relativistic redshift. A gas proportional counter is used to detect the gamma ray and a multi-channel scaler to record the data.

Prerequisite experiment:

Lab B1: Ionizing Radiation Safety.

Lab B4: The Gamma-Ray Spectrometer.


References

  • Absorption of g-rays in matter: R.A. Dunlap, Experimental Physics (Oxford, 1988), pg. 285
  • See Dunlap for the theory of the gas proportional counter and the theory of alpha, beta, and gamma decay, and the photoelectric effect, the Compton effect, and pair production (Ch. 11).
  • Standard sodium-iodide spectra - look at the Scintillation Spectrometry Gamma-Ray Spectrum Catalogue in the lab.
  • Data on 60Co and other isotopes: see chart on the wall, and Table of Radioactive Isotopes (a large book), by Browne and Firestone.
  • For operation of the MCA, see its manual, Series II Personal Computer Analyzer, Operation and Instruction Manual.

Radiation Safety

 

Before doing this experiment, you should do the radiation-safety experiment, to familiarize yourself with the survey meter and the personnel dosimeter.

 

   The 57Co source is an open (non-encapsulated) source.  Do not put your fingers directly on the 57Co.  Keep it in its lead pig when not in use.

      Use the green survey meter (Technical Associates model PUG 1AB, with P-11 probe) to monitor radiation levels in the lab, and wear one of the XETEX model 415A personal dosimeters while in the lab. Record the dosimeter reading at the start of the lab period and at the end. Usual laboratory safety practices should be observed (e.g., no eating in the lab, wash your hands afterwards).

Figure 3.  Nuclear properties of iron-57, from , from Lederer, C.M., J.M. Hollander, and I. Perlman, Table of Isotopes, Sixth Edition (1967), 190.

 

 

Figure 2.  Energy-level scheme for iron-57, from Lederer, C.M., J.M. Hollander, and I. Perlman, Table of Isotopes, Sixth Edition (1967), 191.

 

Figure 4.  table I from Stevens, John G., John C. Travis and James R. DeVoe, Analytical  Chemistry 44, 384 (1972).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6.  Velocity standards.  Source unknown.

 

Figure 5.  Isomer shifts.  Source unknown.