The REDOR transform: direct calculation of internuclear couplings from dipolar-dephasing NMR data

Rotational-echo double-resonance (REDOR) is a dipolar-dephasing NMR technique that provides measurement of dipolar couplings between nuclei in solids, and therefore allows calculation of internuclear distances. Time-domain REDOR dephasing signals do not oscillate in a periodic manner, and the analysis of frequency- and time-domain signals is complicated when discrete or continuous distributions of couplings are present. We introduce a new analytic transform method, analogous to a Fourier transform, that produces resonances at the dipolar coupling frequencies present in the REDOR signal. Computer simulations are used to demonstrate and explore details of the REDOR transform.