Optimizing the ~(13)C-~(14)N REAPDOR NMR Experiment: A Theoretical and Experimental Study

摘要

The optimum ~(14)N pulse lengths in the ~(13)C-~(14)N rotationalecho adiabatic-passage double-resonance (REAPDOR) NMR experiment are determined from calculations and from experiments on samples of glycine and L-alanine. The REAPDOR experiment utilizes the adiabatic passages that ~(14)N spins make between the ~(14)N Zeeman energy levels during the application of a single, short ~(14)N radiofrequency pulse. Use of a short ~(14)N irradiation time of less than one-quarter of a rotor period ensures that the number of ~(14)N spins that undergo more than one passage is minimized. This simplifies calculations describing ~(13)C dipolar dephasing and provides better agreement between calculations and experiments. Recovery of the ~(13)C-~(14)N dipolar couplings and ~(14)N quadrupolar coupling constants and asymmetry parameters is described.