Dynamic localization in spin systems

A dilute collection of spins, when driven coherently by crossed magnetic fi elds of arbitrary and controllable time dependences along the three Cartesi an directions, is shown to exhibit a striking phenomenon in which the azimu thal quantum number remains unchanged for certain resonant combinations of the field intensities and field frequencies. The formalism of dynamic local ization available for the area of charge transport in crystals is shown to provide an approximate but highly efficient analytic method for the study o f this phenomenon. The effect on scattering of probe particles is elucidate d.