Mossbauer spectrum magnetic dipole splitting

Fig. 4.9 Magnetic dipole splitting (nuclear Zeeman effect) in pe and resultant Mossbauer spectrum (schematic). The mean energy of the nuclear states is shifted by the electric monopole interaction which gives rise to the isomer shift 5. Afi. g = Sg/tN and A M,e = refer to the...

We have learned from the preceding chapters that the chemical and physical state of a Mossbauer atom in any kind of solid material can be characterized by way of the hyperfine interactions which manifest themselves in the Mossbauer spectrum by the isomer shift and, where relevant, electric quadrupole and/or magnetic dipole splitting of the resonance lines. On the basis of all the parameters obtainable from a Mossbauer spectrum, it is, in most cases, possible to identify unambiguously one or more chemical species of a given Mossbauer atom occurring in the same material. This - usually called phase analysis by Mossbauer spectroscopy - is nondestructive and widely used in various kinds of physicochemical smdies, for example, the studies of... 

In the course of Mossbauer measurement, the energy of gamma quanta is ordinarily modulated by a mechanical movement of the source relative to the absorber. The spectrum is essentially a plot of Mossbauer transition count rates as a function of velocity of the source relative to the absorber. If no resonance occurs, the spectrum would be a horizontal line with no variations while resonance occurs, there would be a decrease in the intensity at certain velocity values as shown in Figure 5.4. In interpreting the spectrum the Mossbauer parameters can be obtained, i.e. the isomer shift, the electric quadruple splitting, and the magnetic dipole splitting. 

Fig. 4.13 Combined magnetic hyperfine interaction for Fe with strong electric quadrupole interaction. Top left, electric quadrupole splitting of the ground (g) and excited state (e). Top right first-order perturbation by magnetic dipole interaction arising from a weak field along the main component > 0 of the EFG fq = 0). Bottom the resultant Mossbauer spectrum is shown for a single-crystal type measurement with B fixed perpendicular to the y-rays and B oriented along...

Figure 1. Hyperfine interactions for Fe nuclei, showing the nuclear energy level diagram for (a) an unperturbed nucleus (b) electric monopole interaction (isomer shift) (c) electric quadrupole interaction (quadrupole splitting) and (d) magnetic dipole interaction (hyperfine magnetic splitting). Each interaction is shown individually, accompanied by the resulting Mossbauer spectrum.

Since the Mossbauer transition in Fe is of the magnetic dipole type (M ). there are only transitions between nuclear sublevels with A/nj = 0, 1 and A/= +1. This selection rule yields only six transitions between the two ground state sublevels (/= 1/2) and the four excited state sublevels (7=3/2). Figure 9 illustrates the splitting of the nuclear levels, the allowed transitions, and the resulting Fe Mossbauer spectrum, a sextet due to the magnetic hyperfine interaction. 

Fig. 2.6 Typical Fe Mossbauer spectrum resulting from magnetic dipole interaction. The energies of the ground and excited state splitting can be determined as depicted in the figure and described in the text...

Figure 5.2 The influence of magnetic interaction with respect to the excited nuclear state of Fe. (From Schiinemann and Winkler. ) The influence of magnetic interaction with respect to the excited nuclear state of Fe. The latter splits into four sublevels. The selection rule for magnetic dipole (Ml) transitions (AI = 1 and AMi = 0, 1) yields the observed six-line pattern, (a) The Mossbauer spectrum of a metaUic iron foil, (b) The Mossbauer spectrum of the iron carrier protein ferritin. 2000 lOP Publishing Ltd.

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