Chemical shift powder spectra enhanced by multiple-contact cross-polarization under slow magic-angle spinning.

Jésus Raya, Barbara Perrone, Jérôme Hirschinger

Index: J. Magn. Reson. 227 , 93-102, (2013)

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Abstract

A simple multiple-contact cross-polarization (CP) scheme is applied to a powder sample of ferrocene and β-calcium formate under static and magic-angle spinning (MAS) conditions. The method is described analytically through the density matrix formalism. We show that multiple equilibrations-re-equilibrations with the proton spin bath improves the polarization transfer efficiency at short contact times and provides higher signal enhancements than state-of-the art techniques such as adiabatic passage through the Hartmann-Hahn condition CP (APHH-CP) when MAS is applied. The resulting chemical shift powder spectra then are identical to the ones obtained by using ROtor-Directed Exchange of Orientations CP (APHH-RODEO-CP) with intensity gains of a factor 1.1-1.3.Copyright © 2012 Elsevier Inc. All rights reserved.