Spin Hamiltonian case studies

The method presented here for evaluating energy levels from the spin Hamiltonian and then determining the allowed transitions is quite general and can be applied to more complex systems by using the appropriate spin Hamiltonian. Of particular interest in surface studies are molecules for which the g values, as well as the hyperfine coupling constants, are not isotropic. These cases will be discussed in the next two sections. 

The d3 configuration has been extensively studied, particularly in the case of Cr(III) compounds. In general, the results can be fitted to the spin Hamiltonian... 

In an ESR study of the interaction of oxovanadium(IV) cupferronate with basic organic solvents, it has been shown that the coordination of basic solvent molecules leads to the destruction of the dimeric nature of the complex molecules.109 Parameters of the spin Hamiltonian of the ESR spectra of the adducts thus formed in 15 cases have been correlated with the basicity of the organic solvents. By contrast, VO(cupferronate)2 retains its diamagnetic dimeric form in the frozen solution of non-coordinating solvents such as chloroform, carbon tetrachloride, cyclohexane or benzene. 

Magnetic resonance studies have been performed in a number of different materials. In most cases the pressure dependence of the spin-Hamiltonian crystal-field parameters have... 

We will study only one simple case the triangular lattice formed by two-site segments with the one electron per segment. Omitting cumbersome calculations, which are similar to the above one, we obtain the following effective spin Hamiltonians ... 

As in the case of Section III.A, we are now in a position to evaluate the ESR spectrum of a copper complex in solution. As an illustrative example we consider the case where the copper ion occupies a molecular site with axial synunetry. The magnetic parameters characterizing the spin Hamiltonian of the metal ion under study are of the same order of magnitude as those drawn from the literature for the CuCl 2-morpholine complex. ... 

The best studied example for this case is encountered in the bis(diisopropyIdithiocarbamato)iron(lll) chloride [721. Here the spin Hamiltonian... 

EPR is used extensively to detect, identify and follow the fate of radicals involved in polymerization or polymer degradation processes. It is also used extensively to characterize polymeric materials in terms of their morphology, heterogeneity, structural transformations, chain dynamics, and so on [2-5]. For this purpose, one can take advantage of the stable paramagnetic centers present in material to be examined (e.g., residual post-polymerization radicals, or TMIs used as catalytic centers or stabilizers). In most cases, however, external spin probes are added, including spin-labeled macromolecules (see Sections 23.2.1.5 and 23.2.2.1) [6]. The sensitivity and high content of structural information contained in the spin Hamiltonian parameters allow to obtain valuable - and often unique - data on the studied systems [7]. 

General studies on the EPR of copper-exchanged zeolites and on the interpretation of the spectra of nitrogen-containing compounds adsorbed on the same systems have been published by Carl and Larsen. A computational fitting procedure to obtain Cu + spin-Hamiltonian parameters in the case of the simultaneous presence of similar species and of relevant g and A strains is proposed. ... 

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