6.9 XPOLXMOD1—Waveform Modulated Cross-Polarization
01-999162-00 C0402
VNMR 6.1C User Guide: Solid-State NMR
96
For VNMR 5.1 and later
crossp
scales the proton waveform and
tpwrm
scales the X
waveform. The macros
xmodramp
and
xmodcos
create their respective
.DEC
files.
They also serve as a prototype for the creation of custom waveforms.
Parameters
XPOLXMOD1 and XPOLHMOD1make use of the UNITYplus and
UNITY
INOVA
parameters
tpwr
,
tpwrm
,
dpwr
,
cppwr
,
dipolr
,
crossp
,
dblvl2
,
pw
and
cntct
.
See
for a description of these parameters. All other functions (i.e.
toss
, etc) of
XPOLAR1 are also present.
pattern
is a string with the name of the
.DEC
file used for modulation.
pwpuls
is the amplitude of the linear modulator during only the initial proton pulse of
XPOLHMOD1.
crossp
is the amplitude of the proton linear modulator during cross polarization and this
value scales the waveform for XPOLHMOD1.
tpwrm
is the amplitude of the X linear modulator during cross polarization and this value
scales the waveform for XPOLXMOD1.
Waveforms
Two macros are provided to calculate commonly used waveforms, a cosine function and a
ramp. For general waveforms to be used for cross polarization, a duration of 1.0 in the first
column must be 0.2 microseconds.
dmf
and
dres
are not used to control the cross
polarization waveform. You can also set programmed decoupling during acquisition by the
usual procedure using
dmf
and
dres
.
xmodcos(frac,per,amp)
creates a waveform with the following function:
amp*(1.0 - frac/2.0 + (frac/2.0)*cos(t/per))
where
t
is time. The resulting
.DEC
file has the form
xmodcos_frac_per_amp.DEC
where
frac
is x10000 and
per
is in microseconds. The defaults are
per=1/srate
(the
value needed for reference 1) and
amp=1023
.
xmodramp(frac,per,amp)
creates a waveform with the following function:
amp*(1.0 - frac/2.0 + (frac/2.0)*(1.0 - 4.0*t/per))
for
0.0 < t < per/2.0
and
amp*(1.0 - frac/2.0 + (frac/2.0)*(-1.0 + 4.0*t/per))
for per/2.0 < t < per
The resulting
.DEC
file has the form
xmodramp_frac_per_amp.DEC
where
frac
is
x10000 and
per
is in microseconds. The defaults are
per=1/srate
and
amp=1023
.
amp
is the amplitude of the waveform,
amp=1023
. VNMR 5.1 and later software provide
scaling of
amp
with the value of
crossp
or
tpwrm
. For earlier versions, set
amp
to its
fixed value during the pulse sequence (<1023), where
amp=1023
is a full amplitude of the
linear modulator.
frac
is the fraction of modulated intensity, a value between 0 and 1.0.
per
is the period of cosine modulation for 0 to 2
π
radians. For a ramp, the slope is negative
(
1-4t/per
) for
t=0
to
per/2
and positive (
1+4t/per
) for
t=per/2
to
per
. Set
per
relative to
cntct
to obtain a specific shape or ramp during the contact time.
