Office of Research

Center for NMR Spectroscopy

T1 Determination

Once you have accurately calibrated the 90 degree pulse of the methyl iodide sample it is instructive to determine the T1 relaxation time constant. Since the sample is doped with Cr(AcAc)2 this won't take long.

1) Begin by removing the pw array by typing on the command line pw=(your experimentally determined 90 degree pulsewidth), ie. pw=9.3 The obs pulse box should now show only the value of what you put in and should not be pink!

2) Click on the Sequence Tab which brings up a window as shown:

Begin by clicking on the 1) Setup T1 button which will prompt you to enter the minimum T1 expected, the maximum T1 expected and how long you want to run the experiment for. For this sample numbers like T1 min = 0.05, T1 max = 0.8 and time = 0.1 hours give good data.

This dialog sets up an arrayed delay d2 between a 180 degree pulse and a 90 degree pulse as shown :

2) Click the Acq & Obs tab and click on the green Start button to begin collecting the data.
3) Once the data has been collected click the Process T1 button to process the data.
4) Select a peak for which you want the T1 to be determined by clicking the Select View button and expanding around the peak of interest.
5) Set the peak picking threshold with the Set Threshold button.
6) Pres the Analyze T1 button to perform the exponential fitting process which determines the T1
7) Print out the resulting T1 and repeat the process with other peaks.

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