Simulation Zeeman term

For the simulation of ESR spectra one has to solve the spin Hamiltonian of Eq. (10). The easiest way to do this is to regard all the different terms in the spin Hamiltonian as small compared with the electron Zeeman interaction and to use perturbation theory of the first order. The Zeeman term can easily be solved within the eigensystem of the Sz operator (in the main axis system of the g-tensor or S 2=5 for isotropic cases), for instance in the isotropic case ... 

At 245 GHz and at low temperatures (< 50 K), the differences between the populations of triplet energy levels have a perceptible influence on the intensities of the Ams = 1 lines. These differences result essentially from the dominating electron Zeeman term. The outermost peaks in Fig. 4.24, corresponding to maximum zfs have an intensity ratio opposite to that in Fig. 4.15, and therefore D < 0, as confirmed by the spectral simulations in the figure. The value of J was not determined in this case, however. 

Software to simulate spectra of this type by exact methods and by treating the nuclear quadrupole-, the nuclear Zeeman- and the hyperfine terms as a joint small perturbation, are further discussed in Section 3.4.1.7. 

Advanced EMR methods may be used to conduct quantitative measurements of nuclear hyperfine interaction energies, and these data, in turn, may be used as a tool in molecular design because of their direct relation to the frontier orbitals. The Zeeman field dependence of hyperfine spectra enables one to greatly improve the quantitative analysis of hyperfine interaction and assign numeric values to the parametric terms of the spin Hamiltonian. Graphical methods of analysis have been demonstrated that reduce the associated error that comes from a multi-parameter fit of simulations based on an assumed model. The narrow lines inherent to ENDOR and ESEEM enable precise measures of peak position and high-resolution hyperfine analyses on even powder sample materials. In particular, ESEEM can be used to obtain very narrow lines that are distributed at very nearly the zero-field NQI transition frequencies because of a quantum beating process that is associated with... 

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