Zero Filling in 2D 

NMR SPECTROSCOPY
(Xwinnmr on PC, version 3.5)

on 

DPX 200, DPX 300, and DRX 500

Department of Chemistry
University of Oslo
March 2005.

2005.  © F. Rise, B.J. Wik

Log in and start xwinnmr.

1.	Select a 2D dataset with search, for instance a COSY spectrum.  

2.	If you do not own the dataset, make a copy for yourself with the wrd command. 
	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:	EXPERIMENTNAME¿		(use your own expname)
Enter target data set EXPNO:	1¿ (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:	M:¿ (the dataset will go to your home directory on another computer for permanent storage, use D: if you don’t need a permanent copy).
Enter target user name USER:	uio user name¿ 	(your own uio user name).

3. 	Use search again to find the dataset which now is owned by you, then append and apply it 
	to the xwinnmr window and xfb to Fourier transform it in both directions. You can not work 
	properly with a dataset not owned by your self.   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.	Scale the spectrum on the screen with appropriate buttons on the left part of the xwinnmr 
	window, *2 or /2.  Observe that the peaks in the spectrum most probably are "longer" in one 
	dimension  (F1, u1, w1, t1 axis) than the other axis (F2, u2, w2, t2).  The resolution is better 
	in the observed dimension (F2) than the dimension originating from the variable delay (F1) 
	inside the pulse sequence.  

5.	Type eda to see acquisition parameters.  Look for the parameter TD in the F2 dimension - this number if often 1024.  Look then for the TD number in the F1 dimension.  This parameter is often 128.  The lower number in the F1 dimension relative to the F2 dimension is the reason for the elongated peaks in the F1 dimension.  Increasing the TD in F1 dimension drastically 	increases the experiment time.  Eda parameters can only be changed before the experiments starts.  

6.	Type edp to see processing parameters.  Look for the parameter SI (size) in both F1 and F2 
dimension.(size).  edp parameters can be changed after the experiment is finished.  
This is the basis for manipulating the data and making the spectrum look better by ZERO 
FILLING.  With SI (F2) 512 and SI (F1) 64 no zero filling is performed.  Zero filling in the F2 dimension has little effect on the appearance of the spectrum.  Zero filling once or twice does not harm though.  SI (F2) at 1024 and SI (F1) at 128 one zero filling is performed in both dimensions.  With SI (F2) at 1024 and SI (F1) at 256 one zero filling is performed in the F2 dimension and a double zero filling is performed in the other dimension.  Try out different combinations to see how the spectrum changes.  Use increasing numbers in procno (set in edc) for each processing. Plot all the different spectra.

7.	If you are confused with the fact that SI=TD/2 when no zero filling is performed please 
remember that the FID of a 1D spectrum has the double number of points compared to the real part of a 1D spectrum.   

8.	Try also to change WDW between SINE, QSINE, EM and GM.  WDW is the so called 
window function which will give different parts of the FIDs different importance.  A separate manual for WDW will come out shortly.