Electron spin dephasing model for molecular reorientation: exact solutions

Electron spin coherence decay was recently applied to the molecular reorientation of spin probes. We employed the approximation of Van ʹt Hof and Schmidt [C.A. Van ʹt Hof and J. Schmidt, Chem. Phys. Letters 36 (1975) 460]. The approximation was not strictly applicable at low reorientation rates. We found the exact solutions to the coupled differential equations governing the magnetization. The real and imaginary parts of the characteristic matrix yield rate constants and resonance frequency shifts, respectively. The predicted temperature dependence of the coherence decay rates gives a narrower peak and is in better agreement with experiment.