Mdssbauer emission spectroscopy

Fig. 5.4 In order to cover all possible transitions in the absorbing nucleus, the energy of the source radiation is modulated by using the Doppler effect. For 57Fe the required velocities fall in the range between — 1 and +1 cm s-1. In Mdssbauer emission spectroscopy, the sample under investigation is the source, and a single line absorber is used to scan the emission spectrum.

R. Grimm, P. Giitlich, E. Kankeleit, R. Link, Time and temperature dependence of aftereffects in [ Co(phen)3](C104)2-2H20 from time-differential Mdssbauer emission spectroscopy. J. Chem. Phys. 67, 5491 (1977)... 

The Mossbauer effect is the emission and resonant absorption of nuclear y-rays studied under conditions such that the nuclei have negligible recoil velocities when y-rays are emitted or absorbed. This is only achieved by working with solid samples in which the nuclei are held rigidly in a crystal lattice. The energy, and thus the frequency of the y-radiation involved, corresponds to the transition between the ground state and the short-lived excited state of the nuclide concerned. Table 2.4 lists properties of several nuclei which can be observed using Mdssbauer spectroscopy. 

Scherson, D.A., S.L. Gupta, C. Fierro, E.B. Yeager, M.E. Kordesch, J. Eldridge, R.W. Hoffman, and J. Blue (1983). Cobalt tetramethoxyphenyl porphyrin emission Mdssbauer spectroscopy and O2 reduction electrochemical studies. Electrochim. Acta 2%, 1205-1209. 

The nucleus of an isotope suitable for Mdssbauer spectroscopy must have an excited state of moderately low energy (less than about 200 keV) to permit the occurrence of recoilless emission and absorption, and the excited state must be accessible, preferably by the spontaneous decay of a parent isotope with a... 

However, the source, which is supposed to be a material doped with a Mdssbauer nuclide in its excited state caimot be prepared because the half-life is so short that the source would completely decay before one would start the experiment (for Fe, T1/2 10 s). Thus, one has to find a parent nuclide with a reasonably long half-life, which produces the excited Mossbauer level by nuclear decay. This has the consequence that in an emission experiment the dopant element may be different from the Mossbauer active one. In Fe Mdssbauer spectroscopy, this parent nuclide is Co, which decays by electron capture, Co(EC) Fe, with a half-life of 9 months. 

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