The Magnetic Field Effects

Figure 1.1 Effect of interelectronic repulsion, spin-orbit coupling and magnetic field on the energy levels arising from a given 4fn configuration for a free-ion Ln3+. The magnetic field effect is estimated assuming a 1 T field.

Figure 1.2 Energetic structure of a Kramers lanthanide ion in a ligand field evidencing the effect of progressively weaker perturbation. The magnetic field effect is estimated assuming a 1T field.

If the external magnetic field applied to the specimen is H0i the resonance experiment measures the magnetic field effective at the nucleus,... 

Finally, performing multipole expansion of the terms representing the magnetic field effect, as shown in the deduction of Eq. (4.9), we obtain the terms iqu>j aP% and iQwj bpQ, which also have to be added to the righthand sides of (5.94) and (5.93). 

Auzinsh, M.P. (1987). Polarization of laser-excited fluorescence of diatomic molecules and the magnetic-field effect, Opt. Spectrosc. 

Figure 39 (a) Schematic representation of an experimental setup for measuring of three-dimensional anisotropy of the magnetic field effect on photoconductivity (C—crystal, M—mirror), (b) Orientation of the magnetic field B with respect to the crystal axes (a, b, c ). From Ref. 248. 

Figure 40 Three-dimensional anisotropy of the magnetic field effect on photoconduction of a 7 um-thick tetracene single crystal illuminated through a semitransparent gold evaporated anode (cf. Fig. 39a). (a) Relative increase of the photocurrent (iph) when a magnetic field B = 0.5T is rotated perpendicular to the a 6-plane for different orientations of the crystal

Figure 156 A comparison of the magnetic field effects on the EL (curves B and C) of tetracene crystals with (a) low and (b) high DEL component (crystals II and I, respectively, from Fig. 155a). The change of photoluminescence (PL) as a function of B is shown by the broken line (curves A). The effect was measured in two different wavelength regions A and B in the red edge and A and C in the short wavelength and emission maximum. No difference in the shape of field evolution of PL was observed. Reprinted from Ref. 287. Copyright 1975 with permission from Elsevier.

When the magnetic field is applied parallel to the c axis, H c, the symmetry changes from D4h to C4h. In this case the AJU mixes with the A, (Fig. 47), which opens up a new, E 6 polarized radiative channel from A(, to the Ag. Because of the relatively large energetic separation between A a and A u the magnetic field effects should be much weaker in C4h than in Qh, in agreement with the experimental results94). 

If we are to use the radical pair theory to explain the effects of micellization on the cage reaction probability as well as the magnetic field effect, it is mandatory that we be able to observe CIDNP in these systems. In addition, since CIDNP is sensitive to events on the time scale of the radical pair lifetime, detailed analysis of the CIDNP can often lead to mechanistic insight to the dynamics of the radical pair. Below we describe one such result. 

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