Quick method for analysis of anisotropic ESR spectra of particles with a g factor having rhombic symmetry in partially ordered and unordered systems

The exact integral expression describing the form of the anisotropic ESR spectrum of particles with a g factor having rhombic symmetry and a spin S=1/2 has been expanded into a rapidly converging series. This has made it possible to formulate simple rules for the quick analysis of experimental spectra in the case of individual absorption lines with Gaussian and Lorentzian shapes and to determine the corrections associated with the approximate nature of the approach. The rules obtained are universal, i.e., they are equally valid for the ESR spectra of both unordered and partially ordered systems. They can be used to determine the components of the g factor, the width of an individual absorption line, and the orientational distribution functions of the particles in a sample from spectra with sufficient accuracy. The applicability of the expressions obtained has been demonstrated by comparing them with exact computer-simulated ESR spectra.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 738–742, November–December, 1988.