Technique for measurement of the nuclear quadrupole resonance signal frequency

A device for measuring the signal frequency of nuclear quadrupole resonance (NQR) is proposed; it consists of a pulsed incoherent NQR spectrometer, which contains a pulsed self-oscillator, a program block, and a signal receiver. To improve the accuracy of signal frequency measurement, an oscillator of known frequency, a circuit for frequency coparison and selection of the difference frequency, and also a frequency difference period meter have been introduced into the device. The proposed invention enables to detect small shifts in NQR frequencies as a result of external effects, such as pressure, temperature, and internal stresses in the specimen. It greatly simplifies the procedure and increases the accuracy of measurement of some constants of the substance, for instance the quadrupole coupling constant, the asymmetry parameter of the electric field gradient and their derivatives with respect to the external effect parameters