ESR Rigid-Lattice Line Shape in a System of Two Interacting Spins

Abstract

A theory is developed to describe the rigid‐lattice line shape of an electron spin resonance signal which is influenced by dipolar coupling to a second spin. The polarization lifetime T 1 of the dipolar field is assumed short. Computer generated plots are presented. Broadening, peak shifts, and amplitude changes are noted. Under certain conditions no observable broadening is predicted, merely an apparent decrease in spectrum amplitude. Experimental results for a nitroxide radical interacting with a paramagnetic ion are compared with theoretical curves. The results allow calculation of the distance between the two spins. Values for the directional angles of the second spin in the g tensor coordinate system of the observed spin are also calculated.