Model calculations of frequency-domain ESEEM spectra of disordered systems

Abstract

Model calculations were carried out for electron spin-echo envelope modulation (ESEEM), ENDOR, and pulsed ENDOR spectra of spin systems of one electron coupled with an 1 = 1 2 , I = 1 , or I = 3 2 nucleus. On the basis of these simulations, predictions are made of cases for which resolved powder patterns can be expected. In the I = 1 2 case it is demonstrated that in the ESEEM simulations a degradation of the powder lineshape occurs as compared to the ENDOR simulations. Nevertheless, the shape and the symmetry of the bands may give information about the relative sign of the isotropic and the anisotropic hyperfine interaction and may yield an estimate for the magnitude of the hyperfine interaction. In the I = 1 case, the pure quadrupole frequencies can be observed when the nuclear Zeeman interaction is approximately compensated by the isotropic hyperfine interaction in one M s manifold. This limitation is much more strict if I = 3 2 . For this nuclear spin the spectra are extremely complicated and virtually no information can be obtained if this “compensation restriction” is not fulfilled.