Homonuclear dipolar recoupling of arbitrary pairs in multi-spin systems under magic angle spinning: A double-frequency-selective ZQ-SEASHORE experiment

摘要

We describe a useful method for measuring the internuclear distances within arbitrarily selected pairs of like nuclei in dipolar-coupled mull-spin systems. The method uses a combination of the zero-quantum shift-evolutionassisted selective homonuclear recoupling (ZQ-SEASHORE) technique developed by Hu and Tycko [J. Chem. Phys. 2009, 131, 045101] and double-frequency-selective radio-frequency pulse. The double-frequency-selective pulse inverts polarizations of two spins simultaneously, and thus applications of the method presented here are only limited by the spectral resolution, and not by the number of interacting spins. Our experiments demonstrate the validity of the method and present analytical expressions for the dephasing curve.