Measurement of recoil-free fractions in studies of the Mössbauer effect
Abstract
This paper discusses the techniques of measurement of recoil-free fractions ƒ of resonance gamma rays. A theoretical analysis extends the validity of the resonance dip area method, to permit relative ƒ measurements to be made on emission lines of arbitrary shape. The method is also applicable to relative ƒ' measurements on thin absorbers. Some forms of instrumental broadening do not affect the result. A discussion on background intensity measurements includes some techniques for making precise background corrections. Absolute ƒ measurements are discussed in terms of a very wide absorption line, which can be considered to approach the ideal of a "black" resonance absorber. A mixture of fluoroferrates, having a composite line width of more than 1.4 mm/sec, has been developed. The preparation of nearly black absorbers by compounding the mixture with iron enriched in Fe 57, is described in a detailed recipe. The absorbers are so nearly ideal that many ƒ measurements can be made simply, comparing intensities transmitted by a stationary absorber with the corrected intensity transmitted at high Doppler shifts. These absorbers have been used to measure the ƒ of 14.4 keV gamma rays of Fe 57 in Cu, Pt, and Be hosts at room temperature. The results are ƒ( Cu) = 0.175 ± 0.021, ƒ( Pt) = 0.736 ± 0.023 ; ƒ( Be ∥ to c axis) = 0.805 ± 0.028; ƒ( Be ⊥ to c axis) = 0.809 ± 0.028 . Relative ƒ measurements, made with a potassium ferrocyanide absorber, are in agreement with the ratios of the absolute ƒ values.
- Publication:
-
Nuclear Instruments and Methods
- Pub Date:
- April 1964
- DOI:
- 10.1016/0029-554X(64)90132-6
- Bibcode:
- 1964NucIM..27...29H