Protocol: Tancpxfslg  Sequence: tancpxfslg.c  Apptype: solidseq1d

Description: 

Constant, linear or tangent-ramped cross polarization (CP) between 
protons and X followed by FSLG decoupling during acqusition.  Used to 
evaluate FSLG decoupling for use in HETCOR. Tancpxfslg automatically 
sets up FSLG based upon calibrated values of aH90 and pwH90, using the 
macro reset_fslg. 

Additional Software

reset_fslg - This macro uses the calibrated values of pwH90 and aH90 to 
calculate the initial parameters for the fslgH waveform. reset_fslg is 
run from the protocol. 

Setup: 

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

Select Tancpxfslg.  The macro reset_fslg is run from the Tancpxfslg 
protocol.  This macro performs the next 2 steps.

1. Set aHfslg = aH90.  Set pwHfslg = sqrt(2/3)*4.0*pwH90.  The value of 
pwHfslg is rounded to a 100 ns grid and the value of aHfslg is adjusted 
slightly to accomodate the change. 

2. Set ofdHfslg = -1.0/(sqrt(3)*pwHfslg*1e-6)).  Note that ofdHfslg = 
1.0/(sqrt(3)*pwHfslg*1e-6)) is also correct.

Assuming that the decoupler is intitially on resonance, set it to about 
a value about 4000 Hz to lower frequency.  Type: dof = dof - 4000.0 in 
the dec offset entry box on the channels page. FSLG works poorly on 
resonance due to phase transient. See the instructions for Tunerp to 
minimize phase transient. 

Obtain a spectrum of glycine with Tancpxfslg. The methylene 13C should 
split into a 13C-1H dipolar sideband pattern. Each line should be a 
distorted triplet. FSLG decoupling works best for spin rates of 8 to 14 
kHz. 
 
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);  

fslgH:  Module:  yes 
Sequence:  tancpxfslg.c      
Description:  Implements "frequency switched Lee Goldburg", FSLG, 
              homonuclear decoupling on the dec channel.
Parameters:  Sequence Page
       aHfslg - amplitude of the FSLG dec pulses.
       pwHfslg - 360-degree flip on dec, off resonance (the length of 
              each of the two FSLG pulses).  
       nHfslg - FSLG cycles represented in the .DEC file. 
       ofdHfslg - +/- frequency offset of alternating pulses, a 
              negative value indicates that the first pulse has 
              negative offset. 
       ofHfslg - overall frequency offset.
       chHfslg = 'dec' must be set (not shown). 
Implementation: MPSEQ fslg = getfslg("fslgH",0,0.0,0.0,0,1); 
Underscore functions: _MPSEQ functions.   
