24 May 2023
 | 24 May 2023
Status: this preprint is currently under review for the journal MR.

Performance of cross-polarization experiment at conditions of radiofrequency field inhomogeneity and slow to ultrafast MAS

Andrej Šmelko, Jan Blahut, Bernd Reif, and Zdeněk Tošner

Abstract. In this manuscript, we provide an analytical description of the performance of the cross-polarization experiment, including linear ramp and adiabatic tangential sweep modifications, using effective Hamiltonians and simple rotations in 3D space. It is shown that radiofrequency field inhomogeneity induces a reduction of the transfer efficiency at increasing MAS frequencies for both the ramp and the adiabatic CP experiments. The effect depends on the ratio of the dipolar coupling constant and the sample rotation frequency. In particular, our simulations show that for small dipolar couplings (1 kHz) and ultrafast MAS (above 100 kHz) the transfer efficiency is below 40 % when extended contact times up to 20 ms are used and relaxation losses are ignored. New recoupling and magnetization transfer techniques that are designed explicitly to account for inhomogeneous RF fields are needed.

Andrej Šmelko et al.

Status: open (until 21 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on mr-2023-9', Tom Barbara, 24 May 2023 reply
    • AC1: 'Reply on CC1', Zdeněk Tošner, 28 May 2023 reply

Andrej Šmelko et al.

Andrej Šmelko et al.


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Short summary
We present a tutorial on the cross-polarization experiment, which has been the main method of magnetization transfer in solid-state NMR for decades. We explain the principles of its volume-selective performance in the presence of magic angle spinning and radiofrequency field inhomogeneity and the decrease of efficiency with increasing sample rotation frequency.