25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

Amplitude-Modulated High-Power XiX Decoupling

Not scheduled
4h
Harnack House and Henry Ford Building

Harnack House and Henry Ford Building

Board: 74
Poster Posters

Speaker

Mr Matías Chávez (ETH Zürich )

Description

Phase-alternating decoupling (XiX) [1,2] is one of the simplest and efficient high-power decoupling methods in solid-state NMR for faster MAS frequencies. It consists of two pulses of equal length but with a phase difference of 180°. We present variations of this heteronuclear decoupling sequences with improved performance based on numerical calculations of the second-order cross terms [3]. By changing either the amplitude or the length of one of the two pulses, the effective nutation angle of the basic two-pulse element of XiX is changed from 0 to 180°. Such a modification leads to narrower lines compared to the standard high-power XiX scheme. We show experimentally that the two options to implement the effective 180° flip angle, either by amplitude or by pulse-length variation, lead to similar results and significantly longer T2' times compared to standard XiX. For both sequences the optimum parameters can be calculated from experimental settings with simple analytical expressions, resulting in a decoupling scheme, which is easy to set up.

[1] P. Tekely, P. Palmas, D. Canet, Effect of Proton Spin Exchange on the Residual 13C MAS NMR Linewidths. Phase-Modulated Irradiation for Efficient Heteronuclear Decoupling in Rapidly Rotating Solids, J. Magn. Reson. Ser. A. 107 (1994) 129–133.
[2] A. Detken, E.H. Hardy, M. Ernst, B.H. Meier, Simple and efficient decoupling in magic-angle spinning solid-state NMR: the XiX scheme, Chem. Phys. Lett. 356 (2002) 298–304.
[3] K.O. Tan, V. Agarwal, B.H. Meier, M. Ernst, A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance, J. Chem. Phys. 145 (2016) 094201. doi:10.1063/1.4961909.

Primary authors

Mr Matías Chávez (ETH Zürich ) Mr Matías Chávez (ETH Zürich ) Mr Johannes Hellwagner (ETH Zürich) Mr Alexander Malär (ETH Zürich) Dr Vipin Agarwal Prof. Beat Meier Prof. Matthias Ernst

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