Cross polarisation

From NMR Wiki

A basic Cross Polarisation (CP) Experiment goes as follows:

In this example the abundant nucleus was chosen to be H and the observed nucleus is 13C. This also works with other combinations. The abundant nucleus is excited, and its energy is then transfered to the observed nucleus by using a long low power pulse on both channels. The power ratio of these pulses needs the be tuned so that the transition energy for both nuclei is the same.

This method often gives a much stronger signal than direct excitation.