T₁ relaxation times may be determined by using a two pulse experiment in which the delay time (tau) between the two pulses is varied. There is a macro that you can use for T₁ determination. First collect a typical 1D spectrum.
Enter
dot1
This activates the macro for T₁ determination. The macro will prompt you to enter a minimum expected value for T₁ in seconds, a maximum expected T₁ value in seconds and an experiment time in hours. For small molecules try 1, 10 and 0.5 for these values respectively. An array of values for the time between the pulses is generated and displayed in the bottom window. Find the highest array index value (i).
Set p1 to a 180⁰ pulse width, set pw to a 90⁰ pulse width. If necessary see 90⁰ Pulse Width Determination. Enter
go
Once the acquisition is complete, enter
wft ds(highest array index value)
Adjust the spectrum phase so that the peaks are symmetric and all the spectral intensity is above the baseline, then zoom in on a peak of interest. Enter
wft dssh
The peak intensity should be negative in the first few spectra, small in the middle spectra of the group and positive in the last few spectra. If this is not the case then one or more pulse widths and/or delay values may have been misset.
To get the value for T₁, zoom in on the peaks of interest and enter
dpf dll
This labels the lines of the peak at the bottom of the screen and assigns an index number starting with 1 to each line. Enter
fp(index#, index#,...)
to tell the software which spectra to use for the T₁ measurement or
fp
to use all spectra. Then enter
t1
to get a read-out of the T₁ values and associated error for each line at the bottom of the screen. To print this data, enter
printon t1 printoff
A graphical display of each line can be obtained by entering
expl
To print this graph, type
pexpl page
Save the experiment as you would a normal proton spectrum.