Electron Spin Resonance Line Shapes in Partially Oriented Systems

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Abstract
The relaxation theory for paramagnetic molecules dissolved in liquid crystals, having the same elongated shape of the solvent molecules so as to act as probes of their dynamical behavior, has been revised. The diffusion equation is solved as a series expansion of Wigner rotation matrix elements, employing a simplified orientating potential, and the solution is used to evaluate the effects of the molecular fluctuations on the electron spin resonance line shapes. The irreducible components of the dipole and g interaction tensors relax with a spectrum of characteristic times, which are functions of an alignment parameter and cause any contribution to the linewidth to vanish in the limit of complete ordering.