Applications of automatic fittings to powder EPR spectra of free radicals,S>1/2, and coupled systems

Abstract

An automatic fitting procedure has been employed to analyze experimentally studied paramagnetic complexes in powder form by electron paramagnetic resonance (EPR). A least-squares fitting procedure utilizing analytical derivatives of the theoretically calculated spectrum with respect to the g-, zero-field, nuclear quadrupole, and hyperfine tensors was used to refine those parameters. An anisotropic line width could also be fitted. The theoretically calculated spectra were obtained by matrix diagonalization of a general spin Hamiltonian allowing also magnetical[y coupled systems to be analyzed. A VO 2~ S = 1/2 complex showing g and hyperfine anisotropic interactions and free radical systems featuring Aro I =~ 0 transitions due to the direct field effect or the presence of quadrupolar nuclei have been analyzed as well as NO s species on surfaces and radiation defects employed for EPR dosimetry. Analysis of systems with S > 1/2 and magnetically coupled species has also been attempted.

Applications of EPR and ENDOR Spectrum Simulations in Radiation Research

“…Adapted from [35] by permission of the American Chemical Society (2007) could also be reproduced by simulation (not shown) using the second order option in Easyspin [60]. Similar results were obtained in earlier work [35] with software described in [72,73]. The inner features differed significantly between the exact and approximate treatments, however, like for the spectra of ĊF 3 ( Fig.…”

Paramagnetic centers in detonation nanodiamonds studied by CW and pulse EPR

“…Simulation of the EPR-spectrum of the P1-center in nanodiamond was made by an automatic fitting method described in [29].…”

Automatic fitting procedures for EPR spectra of disordered systems: Matrix diagonalization and perturbation methods applied to fluorocarbon radicals

“…The exact method based on matrix diagonalization of the full spin Hamiltonian has been A k were calculated analytically with the help of the Hellmann/Feynman theorem (3) to reduce computation times as described in [10,16]. The Hamiltonian matrix elements are linear functions of the parameters A.…”

“…The derivative with respect to the linewidth for a Voigt function was obtained with the help of (7) . This enters as a factor in the expression for w S ∂ ∂ in the least-squares fit of the line-width w to experiment [10].…”

“…A graphical user interface has been implemented in the Xfit program described in previous reports [10,16]. The interface was written in Java using its graphic library.…”