Zero Filling in 1D 

NMR SPECTROSCOPY
(Xwinnmr for PC, version 3.5)

on 

DPX 200, DPX 300, DRX 500

and

Processing computers

Department of Chemistry
University of Oslo
January 2005.
Version I

2005.  © F. Rise and B. J. Wik

Log in and start xwinnmr.

1.	Click on File followed by search.  Select a disk for instance C:. Select one of your own spectra.

2.	Type wrd¿  this is the command for copying the dataset which is on screen to another disk (home or other place) for permanent storage and at the same time change the ownership of the files.  

Enter target data set NAME:				ZEROFILL¿	(use your own expname)
Enter target data set EXPNO:				2¿					(use the expno seen in the top part of the xwinnmr window).
Enter target data set PROCNO:			1¿					(use the procno seen in the top part of the xwinnmr window).
Enter target disk unit DU:					D:¿ 					(if you want to, you can choose M: and the dataset will go to your home directory)
Enter target user name USER:				uio user name¿ 	(your own user name)

3.	Use search to find the ZEROFILL dataset, then append and apply it to the xwinnmr window and efp to Fourier transform it. If the computer you are using does have another plotter attached than the one used under acquisition use edo (edit output) to select the new plotter.  The data set does regretfully remember the plotter name connected to the computer used to acquire the spectrum.  

4.	efp and apk the spectrum.  Expand a sensible part of the spectrum on the screen..

5.	Type eda to see acquisition parameters.  Look for the parameter TD.  eda parameters can only be changed before the experiments starts.  

6.	Type edp to see processing parameters.  Look for the parameter SI (size).  edp parameters can be changed after the experiment is finished.  

7.	The Re spectrum is presumably consisting of 16k data points.  If so the Im spectrum has 16k data points.  This parameter (data points) is called SI (size).  When SI=TD/2 no zero filling has taken place.  

8.	Use edc to increase the procno (processing numbers) for the following.  Change SI, either by typing SI in the xwinnmr window or by changing SI in the edp window.  Select SI to be 2k, 4k, 8k, 16k, 32k, 64k and 128k.  Do an efp for each individual SI and watch the result on the expanded part of the spectrum on the screen.  The expansion disappears for each efp.  Plot if you like with plot.  

9.	When SI = TD you have zero filled once, when SI = 2TD you have zero filled twice.  What have you done when SI = TD/4 or SI = TD/8?  Which part of the FID are you using?  Why are the spectra looking as they do with low SI?

10.	Zero filling is important in 2D NMR.  Another manual will be provided for this purpose.  An alternative to zero filling in both 1D and 2D is linear prediction which also will have its own manual.  

11.	Zero filling is important with wide sweep widths (wide ppm area).  The sweep width is connected to the acquisition time (AQ) in such a way that the wider the ppm area is the shorter is the AQ time for a given number of data points (TD).  If you do not increase the number of data points when increasing the SW (in hertz or ppm) the AQ drops down.  In certain cases the T1 relaxation is not over at the end of the AQ time.  This will give bad "wiggles" at the baseline of strong peaks.  Zero filling in combination with a WDW (window) function that takes the signal down to zero at the end of the FID (attenuates the signal) can make a bad looking (see above) spectrum better. 

12.	Change procno with edc.  Open edp.  Increase TD to a higher number.  Change LB (line broadening) from 0.3 Hz to 3 Hz.  Keep EM (exponential multiplication) as the wdw (window function).  A separate manual for window functions will appear shortly. 

13.	Efp the FID - watch the difference in appearance!!