Heteronuclear Decoupling by Multiple Rotating Frame Technique

TL;DR

This paper introduces a multiple rotating frame technique for broadband heteronuclear decoupling in NMR, improving performance by adding modulations to reduce chemical shift dispersion effects.

Contribution

It presents a novel decoupling method that generalizes existing techniques and enhances their effectiveness through multiple modulations in the decoupling field.

Findings

Performance improves with more modulations

Known methods are special cases of this approach

Potential applications in solid-state NMR sequence design

Abstract

The paper describes the multiple rotating frame technique for designing modulated rf-fields, that perform broadband heteronuclear decoupling in solution NMR spectroscopy. The decoupling is understood by performing a sequence of coordinate transformations, each of which demodulates a component of the Rf-field to a static component, that progressively averages the chemical shift and dipolar interaction. We show that by increasing the number of modulations in the decoupling field, the ratio of dispersion in the chemical shift to the strength of the rf-field is successively reduced in progressive frames. The known decoupling methods like continuous wave decoupling, TPPM etc, are special cases of this method and their performance improves by adding additional modulations in the decoupling field. The technique is also expected to find use in designing decoupling pulse sequences in Solid State NMR spectroscopy and design of various excitation, inversion and mixing sequences.