Fitting static CSA spectrum...

 Example :  31P spectrum fitted with CSA static model  

CSA Parameters :
  • principal values are sorted |d33-diso|>|d11-diso|>|d22-diso|
  • diso is the isotropic chemical shift 1/3 (d33+d22+d11)
  • dCS is the axiality of the CSA tensor (d33-diso)
  • etaCS is the anisotropy of the CSA tensor etaCS=(d22-d11)/(d33-diso)
Definitions in agreement with Simpson (Aarhus) M.Bak, J.T.Rasmussen, N.C.Nielsen J. Magn. Reson. 147 296-330 (2000)  

It is assumed that you know how to fit Gaussian/Lorentzian lines to a spectrum

There exist several possible strategies... the following describes a possible one.

From a CSA MAS :

  1. Just change the model from CSA MAS to CSA static

  2. Click

From scratch :

  1. Initiate a fit

  2. Add a line

  3.  Changte the mode to CSA Static

  4. Enter CSA parameters or Drag the line on screen (you can adjust amplitude, position and axiality of the tensor.

  5. Click

Step 2 : Optimize the parameters

  1. Click the [Parameters] button to call the [Model Parameters full list] dialog and add a star at the right of the spinning rate to allow its optimization, quit the dialog box.

  2. Click the [Optimize] button to optimize the current solution optimizing Amp/Pos/Width of the ref line, Amp only for the spinning sidebands, and spinning rate.

  3. Save your work, just in case [Menu/Decomposition/Save Fit] or [Menu/Decomposition/Save As Fit]

Line Parameters (Bold parameters are selected for automatic optimization):
: height of the maximum of the N=0 line
    Position : Isotropic Position of the N=0 line (in Hertz, ppm or point depending on the current unit) positions of the spinning sidebands are given by their numbers, the position of the reference line and the spinning rate.
    dCS : the axiality of the CSA tensor (in Hertz, ppm or point depending on the current unit)
    etaCS :  the assymetry paramter of the CSA tensor.