Chapter 6. Solid-State NMR Experiments
89
VNMR 6.1C User Guide: Solid-State NMR 01-999162-00 C0402
phase=2 sets the phase of pwx 90° to the contact pulse and is necessary for measurement
of pwx. Setting phase=1 sets the two phases the same, and all array members of a pwx
array have the same intensity.
6.4 XNOESYSYNC—Rotor Sync Solids Sequence for Exchange
The XNOESYSYNC sequence is the CP/MAS equivalent of a NOESY, but with the first
90
° pulse replaced with cross-polarization. Unlike normal NOESY, the mixing time can be
rotor synchronized. In the solid state, exchange can occur via the spinning sidebands unless
the mixing time is synchronized to the rotor period. When this is done, cross peaks appear
when self or chemical exchange occurs. Figure 36 is a diagram of the sequence.
Macro
The xnoesysync macro sets up parameters for the XNOESYSYNC pulse sequence.
Parameters
pw is the
1
H 90° pulse, in microseconds, for cross-polarization.
p2 is the contact time, in microseconds.
d2 is the evolution time, in seconds.
dm is set to 'nny' for no proton decoupling during the mixing time, or dm is set to 'nyy'
for proton decoupling during the mixing time.
level1 controls decoupler power during cross-polarization.
level1f controls fine decoupler power during cross-polarization.
level2 controls decoupler power during acquisition.
level2f controls fine decoupler power during acquisition time.
phase is 0 for P type, phase is 1 for N type, or phase is 1,2 for phase sensitive. The
Veeman experiment requires phase=0.
Figure 36. XNOESYSYNC Pulse Sequence
1
H
90 p2
d2
pw
13
C
p2
d2
cp90 cp90
mix at
Rotor
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