Application of a Magnetic Field

Application of an external magnetic field alters the nature of some of the magnetic interactions in a RP and also leads to additional terms in the spin Hamiltonian through the electron Zeeman interaction. 

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According to (6.14), spin-spin relaxation may be fast only if the transition energies and are not too different. In some cases, the difference between the transition energies can be varied by the application of a magnetic field and one can then investigate at least qualitatively the validity of (6.14). One example is Fe(N03)3 9H2O [39 1], which has a monoclinic crystal stmcture with space... 

The electron spin resonance spectrum of a free radical or coordination complex with one unpaired electron is the simplest of all forms of spectroscopy. The degeneracy of the electron spin states characterized by the quantum number, ms = 1/2, is lifted by the application of a magnetic field, and transitions between the spin levels are induced by radiation of the appropriate frequency (Figure 1.1). If unpaired electrons in radicals were indistinguishable from free electrons, the only information content of an ESR spectrum would be the integrated intensity, proportional to the radical concentration. Fortunately, an unpaired electron interacts with its environment, and the details of ESR spectra depend on the nature of those interactions. The arrow in Figure 1.1 shows the transitions induced by 0.315 cm-1 radiation. 

Figure 2.94 The lifting of the degeneracy of the Ms = - 1/2, a, and Ms = + 1/2, (l, spin states on the application of a magnetic field of flux density 8. g is the dimensionless g-factor,...

For / = 0 there is obviously no first-order Zeeman splitting however, application of a magnetic field can result in second-order splitting. As such, it is necessary to evaluate the corresponding factor, which isg(j = 2 + 7,(2 + S). 

The application of a magnetic field to the wavefunctions obtained by the procedure described in the previous sections results in the complete removal of the degeneracy of the / multiplet, either pertaining to Kramers or non-Kramers ions, and yields a temperature-dependent population of the different 2/ + 1 components (Figure 1.2) Thus, at low temperatures, large deviations from the Curie law are observed. The effect of the magnetic field is described by the Zeeman Hamiltonian ... 

The need for improved background correction performance has generated considerable interest in applying the Zeeman effect, where the atomic spectral line is split into several polarised components by the application of a magnetic field. With a Zeeman effect instrument background correction is performed at, or very close to, the analyte wavelength without the need for auxiliary light sources. An additional benefit is that double-beam operation is achieved with a very simple optical system. 

By adding the values of 2J + 1 for the ten Russell-Saunders states listed above we see that there are in fact 36 states based upon the configuration 2p3p and that application of a magnetic field gives rise to 36 energy levels. 

Back effect they correspond to a total of 12 quantum states, so that the total for the configuration remains 36, as discussed for the Zeeman case, above. The application of a magnetic field of gradually increasing strength cannot lead to the destruction of quantum states or the formation of new ones, but only to the change in their energy values. 

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