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Hahn Echo Program
for RadioProcessor and
OverviewThe Hahn-Echo experiment applies a 90 degree pulse, waits a period of Tau, and then applies a 180 degree pulse. This causes an echo in the FID response of the sample, which peaks at a duration of Tau after the end of the 180 degree pulse. The Hahn-Echo experiment program is available for download at the bottom of this page, as well as with the other NMR programs in the RadioProcessor section of the SpinAPI Example Downloads.
Figure1. Hahn-Echo Experiment Results (a sample of household cooking oil using a 10.8MHz permanent magnet)
Figure 1 shows the resultant FID response when capturing data continuously during a Hahn-Echo experiment. The large negative spike is caused by the 180 degree pulse being applied. Figure 2, below, shows the pulse sequence used by the RadioProcessor to perform this experiment. Each vertical line is a new instruction, and the names of the durations used are shown above each time range.
Figure2. Hahn Echo Pulse Sequence
Running the Hahn Echo ProgramThe Hahn-Echo program accepts command line parameters to specify the values for each of the pulse program's parameters. It takes the following arguments as inputs:
Table1. Hahn Echo Input Arguments
These arguments must all be passed as input parameters when launching the hahn_echo.exe file. Omitting or passing arguments out of order will cause the program to return an error. To simplify this process, a hahn_echo.bat file is provided. This file allows for easy manipulation of argument values, and ensures that they will passed in the correct order. To use the hahn_echo.bat file simply:
Viewing Hahn Echo ResultsAfter execution of the Hahn Echo program, the output files can be used with external programs to visualize the data.
The LabVIEW NMR Interface can process .txt files. To do this:
The Felix NMR program can process .fid files. To do this simply ensure that the Felix NMR program is installed properly and double-click on the .fid file.
Hahn Echo Acquisition Tips
Setting the input parameters correctly is
critical in obtaining good Hahn Echo data. Below are suggestions for
determining these parameters:
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