We present an off-resonance carbon R-1 rho NMR experiment utilizing weak radiofrequency fields and selective polarization transfers for quantifying chemical-exchange processes in nucleic acids. The experiment extends the range of accessible time scales to similar to 10 ms, and its time-saving feature makes it possible to thoroughly map out dispersion profiles and conduct measurements at natural abundance. The experiment unveiled microsecond-to-millisecond exchange dynamics in a uniformly labeled A-site rRNA and in unlabeled, damaged DNA that would otherwise be difficult to characterize by conventional methods.