Magnetic hyperfine splittings

Fig. 3.4 Calibration spectrum of metallic iron and magnetic hyperfine splitting of the nuclear levels. The values of the hyperfine splitting in a-iron are = 1.677 mm >2 = 6.167mms >3 = 10.657 mm s. The center of the calibration spectrum is defined as velocity zero left). The isomer shift of a specific sample with respect to metallic iron is indicated as 5 (right)...

The magnetic hyperfine splitting allows the determination of the effective magnetic field acting on the nucleus, which may be a superposition of an applied... 

The temperature dependence of the magnetic hyperfine splitting in spectra of interacting nanoparticles may be described by a mean field model [75-77]. In this model it is assumed that the magnetic energy of a particle, p, with volume V and magnetic anisotropy constant K, and which interacts with its neighbor particles, q, can be written... 

Magnetic hyperfine splitting in Ru Mossbauer spectra was observed in the 1960s by Kistner [110, 143] for an absorber of 2.3 at% ruthenium dissolved in metallic iron. The spectra obtained with an unpolarized absorber (a) and with polarized absorbers, i.e., magnetization parallel to incident y-rays (b), and magnetization perpendicular to incident y-rays (c) are shown in Fig. 7.35. The stick spectra on top... 

Au in iron metal Magnetic hyperfine splitting of Au, nuclear moment of 77.3 keV state, IH l of supertransferred field at Au... 

Figure 3.29 Magnetic hyperfine splittings of the nuclear ground state assuming AEq = 0. (Adapted from Figure 2 of reference 24.)...

The magnetic hyperfine splitting, the Zeeman effect, arises from the interaction between the nuclear magnetic dipole moment and the magnetic field H at the nucleus. This interaction gives rise to six transitions the separation between the peaks in the spectrum is proportional to the magnetic field at the nucleus. 

A second form of storage iron is haemosiderin (Weir et al., 1984). This is deposited in humans as a response to the condition of iron overload. Haemosiderin forms as insoluble granules with electron dense cores surrounded by a protein shell. It exists in two forms primary haemosiderin is the result of iron overload due to excessive adsorption of iron in the gut, whereas the secondary form is caused by the numerous blood transfusions which are used to treat thallassaemia (a form of anaemia). Electron diffraction indicated that the iron core in primary haemosiderin is a 3-line ferrihydrite with magnetic hyperfine splitting only below 4 K and, in the secondary form, consists of poorly ordered goethite. As goethite is less soluble in ammonium oxalate buffer solution (pH 3) it has a lower intrinsic toxicity (Mann et al., 1988). 

Qualitatively, there are two conditions that must be met in order to observe a distinct magnetic hyperfine splitting. First, the magnetic splitting must be larger than the linewidth Tn of the y-ray energy distribution, i.e.,... 

In order to examine in which cases the different Mossbauer parameters can be observed, we will in this section make use of parameters R (which will be defined below) where i = 1,2, and 3 refers to the isomer shift, quad-rupole splitting, and magnetic hyperfine splitting, respectively. 

Iron-supported-on-MgO catalysts behave in some ways differently from the above catalyst systems. That is, while the catalytic activity of these metallic-iron particles for the atmospheric-pressure ammonia synthesis depends markedly on particle size in the range 1.5-10 nm (206), the Mossbauer parameters (isomer shift, quadrupole splitting, and magnetic hyperfine splitting) are independent of iron particle size in this range (97). This thus rules out an electronic effect in the interpretation of the effect of particle... 

Beff interacts with the magnetic moment of the nucleus, /< = —g P BI, yielding the magnetic hyperfine splitting of the nuclear ground and excited states that we infer from the Mossbauer spectrum by measuring the transition energies. 

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