We describe a pulsed spectrometer for detection of nuclear quadrupole resonance on the nuclei of nitrogen N-14 with fast Fourier transform. The use of a multipulse sequence, four channel system for data registration and processing permits detection of the nuclear quadrupole resonance (NQR) signal in the presence of strong interference and the piezo effect. Using this spectrometer we registered the NQR signal from an explosive sample of 150 g (92% RDX) at a distance of 22 cm, and the time of detection was 81 s.
The results of a theoretical investigation of two-frequency excitation in pure nuclear quadrupole resonance (NQR) for a spin I = 1 nucleus with a nonaxial electric field gradient are presented. The multipole tensor operator technique is used for the treatment of the one-and two-frequency pulse excitations. The results are applied to the characterization of the two-frequency signal of nitrogen ~4N nuclei. The experiments on sodium nitrite, NaNO2, confirm the presence of additional (two-frequency) echo in the NQR signal. The effect of resonanee offsets on two-frequency NQR is also considered.
The frequency offset effects of the signal interference during steady-state pulse sequences for remote nuclear quadrupole resonance (NQR) were carried out. The applications of the spherical tensor method for pure NQR of spin = 1 for the investigation of these sequences and one pulse sequence, two pulse sequences are presented, too.
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