Sample: Fill a solid-state rotor with finely powdered adamantane.

Spin the sample at 4 kHz and at the magic angle (see Exp. 14.2). Load standard ¹³C NMR parameters. You have to set:

sw: 20 kHz o1: middle of ¹³C spectrum of adamantane o2: middle of ¹H NMR spectrum p1: 4 μs ¹H decoupler pulse, to be varied p2: 5 ms ¹H spin-lock decoupler pulse p3: 5 ms ¹³C spin-lock transmitter pulse dl:4s decoupler attenuation for cross-polarization, to be varied decoupler attenuation for high-power cw decoupling, typically 2 dB less than for cross-polarization; on instruments with no fast power switching use same attenuation as for cross-polarization transmitter attenuation rg: receiver gain for correct ADC input ns: 1 To set the Hartmann–Hahn condition, the r.f. fields on protons and nuclide X, e.g. ¹³C, must be the same, which means that the 90-degree pulse-widths must be the same. De- tect the proton signal of adamantane, spinning at 4 kHz, and set the power level such that the proton 90-degree pulse is 5-6 psec. Then observe the adamantane ¹³C signal with decoupling at this power level, and set the ¹³C power level to be the same as for protons. This will give you the power levels to be used as starting values for the Hart- mann-Hahn adjustment. Leave the proton power level constant, and vary the ¹³C power level until a maximum signal intensity is obtained.

5. Processing

Use standard ¹³C NMR processing with exponential multiplication (lb = 5 Hz) as de- scribed in Experiment 3.2.

6. Result

The figure shows the CP/MAS spectrum of adamantane obtained with one scan using a multinuclear solid-state probe-head with a 7 mm rotor on an AM-400 spectrometer with a wide-bore magnet. The ¹³C signals of adamantane have no significant chemical- shift anisotropy; therefore no spinning side-bands are observed in the spectrum.