Calculation of the Electron Spin Resonance Line Shape of Randomly Oriented Molecules in a Triplet State. I. The Δm=2 Transition with a Constant Linewidth

Abstract

The electron spin resonance line shape for the Δm=2 transition of randomly oriented aromatic molecules in a triplet state is analyzed. This is an extension of the treatment of van der Waals and de Groot to molecules having less than ternary symmetry. In the present paper the spectrum of a molecule is approximated by a Gaussian function of constant width and the electron g tensor is assumed to be isotropic. The various stages of the calculation have been fitted into a computer program, using as input data the principal values of the electron spin-spin coupling tensor. The calculations show that a characteristic structure may be present in the spectrum. The experimental spectra of naphthalene and its deuterated homologue present in effect enough of this structure to make it possible to determine the absolute values of the two constants characterizing the electron spin—spin interaction.