SIMPSON coding examples

SIMPSON Tutorial #3: Cross polarization

by Thomas Vosegaard

This exercise investigates the coherence transfer from 1H to 13C using cross polarization. We will not look at the real spectrum, but only investigate the build-up of signal on 13C.

  1. Look at the input file, beware that the par section contains two lines reading: 'start_operator I2x' and 'detect_operator I1p'. Run the simulation and observe the build-up (3_CP,1.fid)
  2. Change the rf field strength on the 13C channel. This is controlled by the line 'variable rfC 50000' in the par section of the input file. By changing this value you move away from Hartmann-Hahn match.
  3. Change back rfC. All simulations so far have been performed on a single crystal. Change the crystal file to rep168 and observe the resulting fid (3_CP,2.fid)

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spinsys {
  channels 13C 1H
  nuclei 13C 1H
  dipole 1 2 -1500 0 0 0
}

par {
  crystal_file     alpha0beta0
  variable rfC     50000
  variable rfH     50000
  variable tsw     10
  variable index   1

  sw               1e6/tsw
  np               512
  proton_frequency 400e6
  start_operator   I2x
  detect_operator  I1p
  method           direct
  gamma_angles     1
  spin_rate        0
  verbose          1101
}

proc pulseq {} {
  global par
  
  acq_block {
    pulse $par(tsw) $par(rfC) x $par(rfH) x
  }
}

proc main {} {
  global par
  
  set f [fsimpson]
  fsave $f $par(name),$par(index).fid
}
Files:3_CP,1.fid  preview
3_CP,2.fid  preview
3_CP.in
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