Mossbauer light source

In this chapter, we present the principles of conventional Mossbauer spectrometers with radioactive isotopes as the light source Mossbauer experiments with synchrotron radiation are discussed in Chap. 9 including technical principles. Since complete spectrometers, suitable for virtually all the common isotopes, have been commercially available for many years, we refrain from presenting technical details like electronic circuits. We are concerned here with the functional components of a spectrometer, their interaction and synchronization, the different operation modes and proper tuning of the instrument. We discuss the properties of radioactive y-sources to understand the requirements of an efficient y-counting system, and finally we deal with sample preparation and the optimization of Mossbauer absorbers. For further reading on spectrometers and their technical details, we refer to the review articles [1-3]. 

Tsun-Kong) Sham received his PhD in Chemistry from the University of Western Ontario for the studies of Mossbauer spectroscopy. He was on the staff of the Chemistry Department at Brookhaven National Laboratory for ten years before returning to the University of Western Ontario in 1988 and is presently a Professor in Chemistry and the Scientific Director of the Canadian Synchrotron Radiation Facility at the Synchrotron Radiation Center, University of Wisconsin-Madison. He has been involved in synchrotron research since 1975, is a scientific member of the SRI-CAT at the Advanced Photon Source and a Senior Scientific Consultant for the Canadian Light Source (University of Saskatchewan, Saskatoon, Canada). 

The Mars Pathfinder rover carried an Alpha Proton X-ray Spectrometer (APXS), and the two Mars Exploration Rovers (MER - Spirit and Opportunity) carried Alpha Particle X-ray Spectrometers (also called APXS, but in this case more precise versions of the Pathfinder instrument, though without the ability to monitor protons for light element analyses). These instruments contained radioactive curium sources (Fig. 13.16) whose decay produced a-particles, which irradiated target rocks and soils. The resulting characteristic X-rays provided measurements of major and minor element abundances. The MER rovers also carried Mossbauer spectrometers, which yielded information on iron oxidation state. 

The particular dependence /r( ) is of no interest but it should be noted that the centre of gravity of this distribution is shifted by the amount r relative to the transition energy in the source. r = E HMc is the recoil energy imparted to an isolated nucleus of mass M (where c = vacuum speed of light). The energy distribution of the Mossbauer y-quanta ] E) may be considered as Lorentzian ( ) with the full half-width T such that T = Owing to the normalization conditions, /m( ) be written as... 

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