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Tuesday, February 12, 2008

Field Dependence of 13C Line Shapes for Nitrogen Bearing Carbons in the Solid State

The frequency separation between the two peaks in the 1:2 doublets typically observed for 13C nuclei bonded to 14N in 13C CPMAS spectra is inversely dependant on the strength of the magnetic field. As a result narrower resonances are observed for nitrogen bearing carbons at higher field. The figure below shows the 13C CPMAS spectrum of D,L-alanine acquired on both a 200 MHz and a 500 MHz instrument.


Anonymous said...

How people can find this phenomenon during their measurement?

Rob said...

Hi Glen,
Great fan of your blog.

Why is the 4.7T asymmetrical?



Glenn Facey said...

Hi Rob.
The low field spectrum is asymmetric simply because that is the predicted line shape. See the following paper for the details of the line shape:

J. Chem. Phys. 75(4) pp. 1603-1611 (1981).


Glenn Facey said...

If you run you samples at low field, these line shapes just appear for 13C bound to 14N. See this paper for details:
J. Chem. Phys. 75(4) pp. 1603-1611 (1981).