Locked rf Spectrometer for Nuclear Quadrupole Resonance

A technique is described for locking a rf spectrometer to a pure quadrupole resonance signal. Since the quadrupole resonance frequency of a nucleus in a solid can be quite sensitive to changes in temperature and pressure, a quadrupole resonance signal is of potential interest in the measurement of these variables. The application of a locked rf spectrometer as a precise nuclear resonance thermometer is evaluated using the 35Cl resonance of KClO3 powder. The precision of this device as a thermometer is about ±0.002°K, and the system is capable of tracking a temperature change of at least 2°K/min. The locked quadrupole spectrometer appears to have promise as an absolute temperature standard.