A practical guide to ¹H high resolution experiment: rf-field strength

Here we briefly introduce a tip for ¹H high resolution NMR experiments in solid- state, from a practical point of view. This method, in which ¹H homonuclear dipolar interactions are decoupled, has been known as ‘Combination of Rotation And Multiple-Pulse Spectroscopy’ (CRAMPS) for a long time. Although a special probe was originally required, a standard CPMAS probe enables us to perform cutting edge experiments now as only a moderate rf field is enough for a wPMLG experiment, which is one of the best CRAMPS sequences. As rf-field is increased up to 100 kHz, we can observe better resolution, but no further improvement is obtained when the rf- field is stronger than 100 kHz or with higher spinning frequency. The world-class high resolution is achieved with a standard CPMAS probe with an rf-field of 100 kHz and at a moderate spinning frequency.

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