Hyperfine magnetic

Figure 10. Distribution of the hyperfine magnetic fields on trivalent Fe-57 obtained by the Hesse-Rubartsch analysis of the spectra shown in Figure 3.

Fig. 26. Temperature dependence of the hyperfine magnetic field and of the longitudinal relaxation parameter in NpSns. The J = 1/2 Brillouin curve for the temperature dependence of is shown. (Gal et al, )...

More complex spectra are usually obtained. Quadrupole splitting results in two peaks equal in intensity to a first approximation. The amount of splitting is an important parameter, with larger splits occurring for Fe(II) compounds than for Fe(III) compounds. Hyperfine magnetic splitting results in a symmetrical six-peak spectrum with a variation in position and in spread related to the chemical state of the compound. Many superimposed combinations of these as well as broadened peaks and other perturbations are observed when complex materials are examined. 

Fig. 4.7. Dlustiation of (he Zeonan and nuclear hyperfine magnetic interactions.

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.

From the foregoing description of the origins of the internal magnetic field, it might be assumed that all compounds containing unpaired valence electrons would show a hyperfine magnetic splitting effect. There is, however,... 

Mbssbauer spectra are characterized by the following parameters isomer shift (IS), quadrupole splitting (QS) and hyperfine magnetic splitting // rr-... 

Although hyperfine magnetic splitting appears mainly in partially degraded [90] or inhomogeneously doped [91] samples of conducting polymer, its determination may reveal intrinsic contamination of the system or non-uniform distribution of the dopant. 

Under these conditions nucleus X will sense an average hyperfine magnetic field which is not zero because of the Boltzmann distribution of electron spins. The effect of this on the chemical shift of X, which is dependent upon ai and the time average of the z component of the electron spin, is discussed in sect. 4.25.1. 

The magnetic splitting dm is related to the hyperfine magnetic interaction (see Sect. 25.1.5.3). 

The determination of peak intensities becomes a more complicated issue in the case of combined hyperfine magnetic dipole and electric quadrupole interactions (for the case of Fe see, e.g., Kundig (1967) and Housley et al. (1969)), or when the Mossbauer transition has a mixed (most often Ml + E2) multipole character (for the case of Ru see, e.g., Foyt et al. (1975)). Further factors influencing the relative peak intensities will be discussed in O Sect. 25.2.7.5. 

Fig. 4.6. Schematic diagram to show (i) the hyperfine magnetic field (Bht) parallel to Fxx (ii) the hyperfine magnetic field (Bhf) parallel to Fyy...

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