ABSTRACT
The anisotropy or directionality of the interactions between the various magnetic moments in a molecular system containing an unpaired electron, and an external magnetic field is a dominant characteristic of biological electron spin resonance spectroscopy (ESR). In most cases, the nature of the ESR spectra derived from paramagnetic biological systems is very dependent on the relative orientations of the field and orbital motion of the electron. The electron spin echo differs, however, in effect, a relaxation measurement; that is, it represents the modulation of the decay of the xy component of the electron spin magnetization following the spin packet’s absorption of microwave energy. The number of superhyperfine lines depends on the number and spin quantum number of the nuclei that are coupled to the unpaired electrons. The separation of the transitions represents the hyperfine coupling, and can result from any combination of contact and dipolar interactions.
