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.
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
1H
90
p2
d2
pw
13C
p2
d2
cp90
cp90
mix
at
Rotor