WSOLIDS1: MAS: Spin-1/2 -- Spin-S (Diag.) [ Go Home ]

This squeezed picture shows an example for the succesful simulation of a MAS spectrum of a spin-1/2 nucleus that is coupled to a quadrupolar nucleus in a powder sample. It is the ¹³C MAS NMR spectrum of a chloroketosulfone, where carbon is coupled to Cl-35 and Cl-37, and the results have been published in:

K. Eichele, R. E. Wasylishen, J. S. Grossert, A. C. Olivieri:
The Influence of Chlorine-Carbon Dipolar and Indirect Spin-Spin Interactions on High-Resolution Carbon-13 NMR Spectra of Chloroketosulfones in the Solid State.
J. Phys. Chem. 1995, 99, 10110-10113.

Click on the picture to have a better look.

Background

The quadrupolar interaction at a quadrupolar nucleus causes its axis of quantization to be tilted away from the direction of the external magnetic field. This also modifies the spatial dependence of the dipolar interaction, so that magic-angle spinning is not able to suppress the heteronuclear dipolar coupling in the spectrum of the spin-1/2 nucleus, resulting in splittings and broadenings. Similar effects can be transmitted through the indirect spin-spin coupling. If the nuclear quadrupolar coupling constant is on the same order of magnitude as the Larmor frequency of the quadrupolar nucleus, the combined Zeeman-quadrupolar Hamiltonian must be diagonalized at each orientation and averaged over a rotor period to calculate a theoretical spectrum.

[ Go Home ] | last modified: 16.08.2001