Numerical and theoretical analysis of multiquantum magic-angle spinning experiments

Abstract

Using a recent investigation of the Floquet’s theorem for magic-angle spinning nuclear magnetic resonance simulations (NMR), a procedure for computing multiquantum magic-angle spinning spectra is derived. The general formalism which is introduced here can be applied more generally to any solid-state NMR two-dimensional experiments. All interactions and their time dependency are considered during the pulses. Furthermore, for powder patterns, a formal average is possible on γ (the third component of the Euler angle describing the orientation of the crystallite) which leads to great simplifications and to an improved computing efficiency. As an application, the intensity of the spinning sidebands in the two-dimensional multiquantum magic-angle spinning spectrum is investigated. The recently reported appearance of numerous spinning sidebands in the multiquantum dimension is discussed. Such effects appear naturally in the present formalism which provides a theoretical framework for further investigations. Simulations of two-dimensional spectra are compared with experimental data.