Magnetic dipole splitting

Figure 2A. Schematic diagram of Mossbauer parameters isomer shift (6), quadrupole splitting (AEq) and magnetic dipole splitting of the nuclear energy states of 57pe leading to various hyperfine splitting in Mossbauer spectra.

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...

In [49, 76], the line intensities for electric quadrupole and Zeeman (magnetic dipole) splitting and including the anisotropy of the /-factor are also given for / = 2 <-> 7g = 0 transitions (even-even isotopes, e.g., in the rare earth region or in W, Os). 

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... 

Energy-level scheme and resultant spectra for the combined hyperfine interactions with a strong magnetic field. Part (a) represents the nuclear ground and excited states without hyperfine interactions, (b) with isomer shift, (c) the pure magnetic dipole splitting of ground and excited states, and (d) with additional line shifts due to first-order electric... 

Magnetic dipole interaction Magnetic dipole moment ii 0 (I>0) H 0 Nuclear states I > split into 21 - - 1 substates I, mj > with mi = -b I, +1-1,. .., —I => Magnetic dipole splitting AEm... 

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. 

Magnetic dipole splitting provides information eoneeming spin interaction processes. Information can be derived with referenee to the electron configuration, magnetic relaxation, magnetic moment, spin value, magnetic transition... 

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...

In experiments with magnetic fields between 13 and 55 mT (130-550 G) applied to the single crystal source, the authors of [58] observed magnetic dipole interaction in addition to electric quadmpole splitting in a reduced spectrum (Fig. 7.22) [58]. They determined the magnetic moment of the excited 1/2 state to be U(l/2 ) = +(0.58 0.03))In-... 

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. 

Fig. 7.4 Top Nuclear energy levels of Fe as shifted by electrical monopole (left), or as split by electrical quadrupole (center) or by magnetic dipole interaction (right), schematized for hematite at room temperature (5 > 0 vs. a-Fe, EQ < 0, Bhf 0). Bottom Schematic Mossbauer spectra corresponding to the energy levels schematized on top (J. FriedI, unpubl.).

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