Protocol: Hetcorsamlgcp2d_1  Sequence: hetcorsamlgcp2d_1.c  Apptype: solidseq1d

Description:

    H to X HETCOR using SAMn during F1 followed by a Lee-Goldburg CP and
    acquisition on X with TPPM or SPINAL decoupling.

    Apply a frequency offset to pwH90(1), samnH and pwH90(2) to offset F1
    SAM without disturbing CP or decoupling on resonance. tHmix is optional 
    spin-diffusion mixing period. 

    SAM provides F1 precession about Zed.  pwH90(3) and a tiltH pulse with 
    amplitude aH90 allow an offset, Lee-Goldburg CP.  

    SAM is recommended for Spinner Speeds above 25 kHz where synchronization 
    conditions may affect FSLG or PMLG. 

Additional Software:

reset_hetcorsamlgcp2d_1 - This macro uses the calibrated values of pwH90 
and aH90 to calculate the intial parameters for the samH waveform.  This 
macro is run from the protocol.

Setup:

Load a calibrated data set and select the protocol Hetcorsamlgcp2d_1. For a
new nucleus calibrate CP with Onepul and Tancpx and then set up Lee
Goldburg CP with Lgcp. Then select the protocol Hetcorsamlgcp2d_1.

Select the desired decoupling method, TPPM or SPINAL. The manual file
onepul describes calibration of decoupling.

Lee-Goldburg CP and decoupling should use an optimum dof value, calibrated
for CP. 

The macro reset_hetcorsamlgcp2d_1 is run from the Hetcorsamlgcp2d_1 
protocol.  This macro performs the next 4 steps.

1. Set aHsam = aH90.  Set pwHtilt = pwH90*35.3/90.0.  aH90 automatically
determines the tilt-pulse amplitude. 
2. Set pwHsam = 1.0/srate.  pwHfslg is rounded to a qHsam*100 ns 
grid and srate is adjusted to accommodate the change. 
3. Set qHsam = 3 if it is not set - leave values alone if qHsam > 3.
Note that qHsam will affect the exact rounded value of pwHsam and srate.
4. Set nHsam = 1 if nHsam < 1. nHsam is the number of SAM cycles in the 
F1 period and it will be reset by the sequence for each F1 increment. 
4. Set sw1 = srate to provide synchronized data collection in F1. 

The value of aHsam is independent of pwHsam. See the discussion of scalesw1. 

Set pwX180 = 0.0 to *not* place an X refocusing pulse in the middle of the
F1 delay.  Most HETCOR's are run without a refocussing pulse.  A
refocusing pulse is only desirable if the X-H J-coupling is limiting
proton resolution.  MAS is adequate to remove the X-H dipolar
interaction.   If a refocusing pulse is desired then the spin rate must
be synchronized with the F1 dwell so that the refocusing pulse falls at
a multiple of the rotor period

For pwH90 (More page) and samnH, set the parameter with  the "of"
prefix in the range -1000 to -5000.  Note that the value of "of" is 
applied to the first two 90 degree pulses and the SAM. The F1 spectrum 
will be to the left of the center and SAM resolution will be the best 
with this offset if phase transient is present.  There may be a center
spike in F1. Be sure all lines are to the left of the spike.

Collect a 2D dataset and process with wft2da.  Adjust ni to accommodate
greater or lesser proton resolution of the sample in F1.

HETCOR is very sensitive to phase transient on the proton channel
(though SAM may be less sensitive than FSLG. Side effects of a large
transient are a short T2 and an offset of the spectrum in F1.  It is
recommended that one spend significant effort to remove phase transient
for HETCOR.  The procedure for phase-transient removal is in the manual
file tunerp.

A good sample for a HETCOR setup is natural abundance glycine. A quick
HETCOR can be ni = 64, nt = 4, d1 = 1 and ss = 4.  Hetcorsamlgcp2d_1 works
best with spin rate above 15 kHz.  Calibrate the pwH90 = 2.5 us to do
100 kHz SAM during F1 if the probe has the appropriate specification. The 
best field strength is a function of both decoupling linewidth and scale. 
Choose the best value by trial. With a good result one will see a 
substantial splitting in the two upfield methylene lines - from 20% to 
the baseline depending upon the probe and calibration. In a Solenoid 
probe HETCOR can be improved by constricting sample to 50% of the coil 
width.

The indirect axis of HETCOR is scaled by the value scalesw1. Best value 
will depend on aHsam (the field strength) and will usually be 1.0 to 1.2
scalesw1 - 1/MPscale , where MPscale is the published values 0.8 to 1.0. 
It will be necessary to adjust scalesw1 to obtain the correct ppm scale.
A rough calibration with glycine is obtained by putting two cursors on 
the two methylene lines of glycine. On the command line type scalesw1 =
dfrq/delta.  In general, set two lines with a known ppm difference Dppm
and set scalesw1 = Dppm*dfrq/delta where Dppm is the shift difference.

To reference F1 of a scaled HETCOR spectrum put a cursor on the peak
with a known ppm value and type rl1(ppm*dfrq/scalesw1). Note that
HETCOR spectra are displayed with axis ='pd' and refsource = 'dfrq'.

Parameter  Groups:

90H:  Module:  yes - the offset is used for the first two pwH90 pulses.
Sequence:  hetcorsamlgcp2d_1.c
Description:  Provides a 90-degree pulse on dec that can be used
              as a preparation pulse.
Parameters:  Channels Page
       aH90  - the amplitude of the pulse.
       pwH90 - the pulse length.
       ofH90 - offset of pwH90 pulses (1) and (2). 
       chH90 = 'dec' must be set (not shown).

Implementation:  SHAPE p1 = getpulse("90H", 0.0,0.0,1,0);
                 SHAPE p2 = getpulse("90H", sh.phAccum,sh.phInt,2,0);
Underscore function: _shape(p1,ph1H90);  _shape(p2,ph2H90);
      ph1H90 and ph2H90 are the overall phase tables of the pulses. 

Note: the starting phase of SHAPE p2 is updated for each F1 increment
      using update_shape().  

Note: pwH90 (3) is used directly in a decrgpulse() statement with 
      phase ph3H90 and offset determined by dof. 

pwHtilt: an individaul parameter set to 35.3*pwH90/90.0. The tiltH 
      pulse uses the amplitude aH90. 

samH:  Module:  yes
Sequence:  hetcorsamlgcp2d_1.c
Description:  Implements SAMn decoupling on H where the qHsam = 'n',
              the number of cosine cycles per rotor period.       
Parameters:  Sequence Page
       aHsam - amplitude of SAM on dec. 
       pwHsam - 1 rotor period, set srate = 1.0e6/pwHsam. 
       qHsam - cosine cycles per period pwHsam. 
       nHsam* - periods of pwHsam represented in the waveform. 
       ofHsam - overall frequency offset.
       chHsam = 'dec' must be set (not shown).
Implementation: MPSEQ sh = getsamn("samH",0,p1.par.phAccum,p1.par.phInt,1,0);
Underscore functions: _MPSEQ functions.

Note: The starting phase of MPSEQ sh is updated for each F1 increment
      using update_mpseq().  

Note:* nHsam is updated by the pulse sequence and is the number of 
       periods of pwHsam in the F1 period. 

cpHX:  Module:  yes
Sequence:  tancpxyr.c
Description:  Implements constant, linear or tangent-ramped cross
              polarization from dec2 to obs.
Parameters:  Sequence Page
       shHX - 'c', constant, 'l', linear and 't', tangent shape on
               the channel designated with chHX.
       chHX - the variable-amplitude channel, 'fr' from or 'to', to.
       aHhx - median amplitude of the dec2 channel.
       aXhx - median amplitude of the obs channel.
       bHX -  +/- tangent curvature (>0 to 1.0e5).
       dHX -  amplitude width of the ramp. A negative width sets a
              ramp that starts high and decreases in amplitude.
       tHX -  contact time
       ofHX - overall offset on the variable channel
       frHX = 'dec2' -  channel with the initial polarization (must
              be set - not shown).
       toHX = 'obs' -  channel with the final polarization (must be
              set - not shown).
Implementation:  CP hx = getcp("HX",0.0,0.0,0,1);
Underscore functions: _cp_(hx, phHhx, phXhx);

Hseq:  Module:  yes
Sequence:  tancpx.c
Description:  Chooses SPINAL or TPPM decoupling on the dec2 channel
              during acquisition.
Parameters:  Sequence Page - Hspinal and Htppm groups overlap.
       Hseq - chooses the decoupling sequence, TPPM or SPINAL.
Implementation:  DSEQ dec = getdseq("H");  The router implements
              getspinal() or gettppm().
Underscore functions: _dseqon(dec); runs _tppm(); or _spinal();
              _dseqoff(dec); runs decprgoff();

Hspinal:  Module:  yes
Sequence:  tancpx.c
Description:  Implements SPINAL decoupling on the dec channel during
              acquisition.
Parameters:  Sequence Page
       aHspinal - amplitude of the dec channel.
       pwHspinal - approximate 180-degree flip angle on resonance.
       phHspinal - +/- small angle phase. SPINAL64 is implemented
              with phases = +/- 1.0, +/- 1.5 and +/-2.0 times phHspinal.
       chHspinal = 'dec' must be set (not shown).
Implementation: SPINAL dec = getspinal("H"); or DSEQ dec = getdseq("H");
Underscore functions: _spinal(dec); and decprgoff(); or _dseqon(dec);
              and _dseqoff(dec);

Htppm:  Module:  yes
Sequence:  tancpx.c
Description:  Implements TPPM decoupling on the dec2 channel during
              acquisition.
Parameters:  Sequence Page
       aHtppm - amplitude of the dec2 channel.
       pwHtppm - approximate 180-degree flip angle on resonance.
       phHtppm - +/- small angle phase. TPPM is implemented
              with phases = +/- 1.0 times phHtppm for alternating pulses.
       chHtppm = 'dec' must be set (not shown).
Implementation: TPPM dec = gettppm("H"); or DSEQ dec = getdseq("H");
Underscore functions: _tppmon(dec); and decprgoff(); or _dseqon(dec);
              and _dseqoff(dec);

