ENDOR simulation software

HYSCORE single crystal spectra of irradiated /-alanine in Fig. 2.24(a) show an interaction with nuclei (/ = 1) that is too weak to be resolved in CW-ESR and ENDOR spectra. As for I = Vi the nuclear transitions are identified most conveniently by a contour map of the type shown in Fig. 2.24. Software for the data processing to obtain the map is usually provided with commercial instruments. The interpretation is, however, complicated by the quadrupole interaction of the nucleus. The procedure to analyse the data employed in [41] was analogous to that applied for measurements of hfc and nqc tensors by ENDOR (Section 2.2.22). The analysis was supported by simulations (Fig. 2.24(b)) which also accounted for the lines observed in the left quadrant due to the low nuclear frequency of " N at X-band. The results were interpreted as due to a deaminated radical, H3CCHCOO , weakly interacting with the released ammonia group. 

Abstract The analysis of ESR, ENDOR, and ESEEM data to extract the resonance parameters is treated. Free radicals in solution are mainly identified by their hyper-fine couplings (hfc). The analysis of ESR and ENDOR spectra by visual inspection and by computer simulation is discussed. The Schonland method to obtain the principal values and directions of the anisotropic g- and hfc- tensors from single crystal ESR and ENDOR data is presented. The modifications needed when 5 > A or / > A to obtain zero-field splitting ( i) or nuclear quadrupole coupling (nqc) tensors are considered. Examples of simulations to extract g-, hfc-, Tfs-, and n c-tensors from ESR and ENDOR spectra of disordered systems are presented. Simulation methods in pulsed ESR (1- and 2-dimensional ESEEM) studies are exemplified. Internet addresses for down-loading software for the simulation of ESR, ENDOR, and ESEEM spectra are provided. Software for the analysis of single crystal data by the Schonland method is also available. 

Table 3.3 Software for simulation of isotropic ESR and ENDOR spectra S = Vi)...

Several factors unique for ENDOR affect the intensities, i.e. magnetic relaxation, hyperfine enhancement, and angular selection. The two first effects also affect spectra of liquid and crystalline samples, while the third is typical for powder spectra of species with anisotropic g-values. Methods that take the two latter effects into account have been developed and are usually incorporated in software developed for the simulation of ENDOR spectra in the solid state. Simulations that take magnetic relaxation effects into account have been employed only to analyse ENDOR spectra in the liquid state [2]. It is possible that the commonly observed poor agreement between experimental and simulated intensities in the solid state is at least in part due to relaxation effects that are not taken into account in any software we are aware of. 

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