Heteronuclear dipolar recoupling in multiple-spin system under fast magic-angle spinning

We show that the C-REDOR sequence can be modified according to the framework of rotary-REDOR to realize heteronuclear recoupling in multiple-spin systems. Because of the inherent favorable properties of C-REDOR with respect to rf inhomogeneity, our approach is anticipated to find useful applications in biological research. Furthermore, active rotor synchronization of the windowless C-REDOR is implemented by an ad hoc shortening of the pulse elements. Numerical simulations and experiments measured for [U-13C,15N]-l-alanine are used to validate our approach.