Setting up ¹³C CP/MAS experiments

Abstract

The 13C cross‐polarization (CP) technique combined with magic angle spinning (MAS) has become one of the more commonly performed solid‐state nuclear magnetic resonance (NMR) experiments. The basics of initially setting up the experiment are given and used to illustrate such NMR phenomena as rotational echoes, homogeneous and inhomogeneous interactions, continuous wave 1H decoupling, and coupling of quadrupolar 14N nuclei to 13C nuclei. The polarization transfer from the protons to the carbons is described briefly with the usual thermodynamic and quantum mechanical models. The setup and use of the experiment for routine analyses are discussed. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 37–49, 2004.

27Al NMR Studies of Aluminosilicate Glasses

“…The "magic angle" condition is readily arranged by monitoring the response of the rotational echoes from the STs of 79 Br (S ¼ 3/2) in a powder of KBr [150], preferably using a MAS rate around 5-10 kHz. This is performed by varying the position of the "stator" (which holds the rotor in position by flowing air or nitrogen gas), and thereby the inclination angle between the rotor axis and B 0 [150,151]. The periodic MAS modulation of the quadrupolar frequency makes rotational echoes forming at every multiple of the rotational period (nτ r ).…”

“…A subsequent fine tuning must zoom in the signal-portion ≳8 ms, usually requiring signal averaging of (typically) 32-128 signal transients to allow observation of the weakest rotational echoes. We refer to Taylor for additional information about the magic-angle setting [151]. 23 Na NMR on NaNO 3 is also suitable for locating β m ; while allowing for more accurate angle settings due to the higher quadrupolar coupling constant (C Q ¼ 337 kHz) compared with 79 Br in KBr (C Q % 100 kHz), the calibration is more time consuming owing to the slower T 1 relaxation relative to the KBr case, for which relaxation delays of %0.25 s is readily utilized, only being limited by rf-heating effects of the MAS probehead.…”

Tutorial on analytic theory for cross‐polarization in solid state NMR

“…This article aims to be a didactic, explicit development of the core results for cross-polarization in static and magic-angle spinning conditions. There are many treatments of CP in texts and articles, (1,(11)(12)(13)(14)(15)(16)(17) as well as an excellent set of papers on experimental aspects of CP/MAS (18,19). This article attempts to provide a tutorial of the theory to complement prior reports that will aid in learning solid-state NMR (SSNMR) theory or serve as a refresher.…”

29Si NMR Chemical Shift Tensor and Electronic Structure of 7-Silanorbornadienes

“…Solid-state 29 Si{ 1 H} static and cross-polarization (CP) magic angle spinning (MAS) [27,28] measurements for compounds anti-4a, b were carried out on a Bruker spectrometer at an external magnetic field of 9.4T (i.e., a 29 Si resonance frequency of 79.5 MHz) using a standard Bruker 4 mm double-resonance H-X MAS probe. The CP spectra were recorded with a cross-polarization time of 2 ms, and composite pulse 1 H decoupling was applied during the acquisition.…”