207Pb NMR detection of spinning-induced temperature gradients in MAS rotors

The position of the 207Pb MAS NMR resonance from Pb(NO3)2 at a given inlet temperature of the spinning air depends on the rotation frequency, the diameter and geometry of the rotor, the position of the sample in the rotor, and the bearing air pressure. Taking these effects into consideration, the use of Pb(NO3)2 as a chemical shift thermometer gives a temperature accuracy of (0.1 K for a very small sample and a MAS-induced temperature gradient of 4 K for a 4 mm sample spun at 10 kHz.