Spectral diffusion of saturation and rotational motions

When the rotational correlation time is slower than 10 second, the spectra become insensitive to motion, resembling powder spectra. However, since the spin-lattice 

Spectral diffusion of saturation can be detected in various ways, including electron-electron double resonance (ELDOR), effects on adiabatic rapid passage spectra, saturation recovery, and CW saturation. Of these, ELDOR is by far the most attractive in principle, because the effect is observed directly. Unfortunately, the requisite equipment is not widely available. We look forward to increased use of ELDOR, particularly time-resolved ELDOR, to study special motions of slowly diffusing spin labels. 

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