Protocol: Lgcp  Sequence: lgcp.c  Apptype: solidseq1d

Description:

X Lee-Goldburg cross polarization (CP) between protons and X with a
choice of SPINAL or TPPM decoupling. Used for selective CP with
suppression of homonuclear dipolar interactions and for setup of Lee-
Goldburg HETCOR.

Setup:

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

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

Before running Lee-Goldburg CP use Tancpx to calibrate aHhx with a
known field strength.  This can be done by calibrating CP with aH90 =
aHhx and then determining pwH90.  The proton field strength is ?B1H =
1/(4.0*pwH90). Match the Hartmann Hahn condition by varying aXhx as
needed.  It is helpful to array aXhx and note the positions of the
intensity maxima.

Select the protocol Lgcp. Set ofHX = ?B1H/sqrt(2) and continue to use
aHhx from the previous step.  Note that ofHX = - ?B1H/sqrt(2) is
incorrect relative to the phase cycles of pwH90 and pwHtilt.

Recalibrate the proton excitation pulse pwH90 to the value usually used
for proton excitation if desired.

After recalibration of pwH90 set pwHtilt = pwH90*35.3/90.0.  Set Shape
= 'const' and Channel = 'from'. Match the Hartmann-Hahn condition by
varying aXhx as needed. It is helpful to array aXhx and note the
positions of the intensity maxima. You will note that the pattern is
shifted to higher amplitude because of the offset.   Choose one of the
maxima for CP.

Note: the CP module only allows an offset on the channel selected in
Channel.  Since this must be 'from' or protons, a ramped amplitude
cannot be applied to X.  It is possible to use a ramp on protons,
though that is not a usual practice for Lee-Goldburg CP.

Array the contact time tXhx for the Lee-Goldburg CP. You will find that
non-protonated X nuclei cross polarize weakly for all contact times and
that protonated nuclei polarize to their fullest extent with a short
contact time.

Lee-Goldburg CP cross polarization can only occur through an X-H
dipolar mechanism and X-H-H three spin CP is suppressed. A long contact
time however can increase the importance of long range X-H
interactions. This distinction is important when using Lee Goldburg CP
for Lee-Goldburg HETCOR. Spin diffusion is suppressed and long distance
X-H correlations can be recognized.

Note that signal to noise of Lgcp is about 50% of that of Tancpx.

Parameter Groups:

90H:  Module:  no
Sequence:  tancpx.c
Description:  Provides a 90-degree pulse on dec that can be used as a
              preparation pulse. Also used to store the dec calibration.
Parameters:  Channels Page
       aH90  - the amplitude of the pulse.
       pwH90 - the pulse length.

cpHX:  Module:  yes
Sequence:  tancpx.c
Description:  Implements constant, linear or tangent-ramped cross
              polarization from dec 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 dec 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 = 'dec' -  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 dec channel
              during acquisition.
Parameters: Sequence Page - the 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 dec channel during
             acquisition.
Parameters:  Sequence Page
       aHtppm - amplitude of the dec 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);

