UXL203
TLC-26SEP89CD
19JUL91UD
90-Degree Pulse Width Determination
In order to determine the 90 degree pulse width, you must first run a simple experiment to
determine the 360 degree pulse width. It is important to allow enough time for the protons to relax
inbetween pulses. Setting D1 equal to 60 seconds should be enough time. Once the 360 degree null has
been established, divide the 360 degree value by four will give the 90 degree pulse width in microseconds.
The illustration below shows a series of signals for which a sine wave of intensities can be seen.
(Illustration taken from handout #032 "Determination of 90 degree and 360 degree Pulse Widths".)
SETTING UP THE EXPERIMENT:
To set up a 90-degree pulse width determination test on the XL200, you need to first setup the
experiment in JEXP4. Insert the 3% CHCl3 in d6-acetone sample into the probe. Lock, phase and shim on
the sample. Type SETUP(H,ACETON). Change NT=1 and take one acquisition to make sure the
receiver lights do not flash. Then, enter the following changes to the parameter table, LB=N, D1=60,
NP=8000, PW(1)=20, 25, 30, 35, 40, 45, 50, 55, 60. If you are not set up in EXP4, do so now by moving
the parameter table from EXP1 to EXP4. Type MP(1,4) and JEXP4. Check the array values by typing
DA1, they should be exactly what you entered above. Do an SU and a GO when ready. While you are
acquiring, you should notice the top of the screen will have: ACQUISITION:4 CT, 1 FID:1, and PROC:4
displayed. The number "4" indicates experiment 4, the number after " FID:" indicates the fid in the array
that is being processed or acquired. When the experiment has completed, the message EXP4 ACQUISTION
COMPLETE CT=1 is displayed. Type a WFT(ALL) to weight and fourier transform the fid's. Display the
array in the middle of the screen by entering VP=100. Phase the first spectrum in the array by typing
DS(1), and APH. Enter DSSH to display the spectra stacked horizontally. The diagram below shows a
proton 90 degree pulse width determination spectrum; the 360 degree null is between 40 to 45
microseconds. The 360 degree null is at 44 microseconds for proton on the XL200, so therefore, dividing
44 by 4 gives the 90 degree pulse width of 11 microseconds.
(Diagram of PW90 test taken on the XL200 Spectrometer)
Plot out the spectra using PL(ALL), include the parameter table PAP. List the PW array on the
printer by first entering DA1 to list the pulse width values on the screen and type BDUMP to print. Save
the file by using
SVF(DSK5.PW). To retrieve the file, type RT(DSK5.PW). To complete this experiment, insert the lab
sample and secure lock. Sign the log book and log off reslog.
Note: For additional information regarding 90-degree and 360 degree pulse width determination, see
handout #032 located in the blue bins in room 146 RAL.