Bruker BioSpin Solid State NMR, User Manual

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Basic MQ-MAS
User Manual Version 002 BRUKER BIOSPIN 229 (327)
Figure 17.11.Slices and Simulations of the 18.8 T
17
O MQMAS of NaPO3.
Fitted parameters are A) Qcc
≈
7.7 MHz, h
≈
0.36, diso
≈
125 ppm and B) Qcc
≈
4.5 MHz, h
≈
0.16, diso
≈
87 ppm for the upper peak (sample courtesy of Alexan-
drine Flambard, LCPS, Univ. de Lille).
Spectra that are sheared can be evaluated graphically as follows, as shown in
Figure 17.12.
. In addition to the (red) isotropic chemical shift axis indicated as
“axis CS” with the slope (F2)/ (F1) = 1 there are two more lines drawn. The
(blue) axis indicated as “axis Qis” is the quadrupole induced shift axis with the
slope
(F2)/ (F1) = -17/10. This axis is identical for all different spins I and all
orders p of the MQMAS experiments. This axis can be shifted, retaining the same
slope, so that it intersects a spectral line in its centre of gravity. Through the inter-
section point of the Qis axis with the CS axis a third line can be drawn parallel to
the F2 axis. This is the dotted black line in
Figure 17.12.
. The shift value that is
read from the F1 axis at this position is the isotropic chemical shift of that particu-
lar site, and the Qis is then given by
(Eq. 17.2)
.
Δδ Δδ
Δδ Δδ