Two-dimensional NQR using ultra-broadband electronics

• Published in: Journal of magnetic resonance (1997) 2014-03, Vol.240, p.16-23
• Main Authors: Mandal, S., Song, Y.-Q.
• Format: Article
• Language: English
• Subjects: Algorithms; Broadband; Coiling; Computer Simulation; Detection of drugs and explosives; Electromagnetic Fields; Excitation; Explosive Agents - analysis; Glycine - analysis; Hardware; Magnetic Resonance Spectroscopy - methods; Nitrates - chemistry; NQR; Nuclear magnetic resonance; Pharmaceutical Preparations - analysis; Potassium Compounds - chemistry; Reproducibility of Results; Robustness; Single-coil; Spectra; Tuning; Two dimensional; Two-dimensional NQR
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2014.01.001

[Display omitted] •Developed an ultra-broadband (“non-resonant”) MR system with un-tuned sample coil.•Used system to perform simple multi-frequency NQR experiments with a single coil.•Repeated the multi-frequency experiments to build two-dimensional (2D) NQR spectra.•These 2D spectra reveal coupling between 14N NQR lines arising from the same site.•Experimentally verified using several solid powder samples, including mixtures. We have recently developed an ultra-broadband instrument that can effectively excite and detect NMR and NQR signals over a wide frequency range. Our current system operates between 100kHz and 3.2MHz using an un-tuned sample coil. The major benefits of this instrument compared to conventional NQR/NMR systems include increased robustness, ease of use (in particular for multi-frequency experiments), and elimination of the need for tuning adjustments in the hardware. Here we describe its use for performing two-dimensional (2D) scans, which allow improved interpretation of complex NQR spectra by detecting the connected resonances. Our method relies on population transfers between the three energy levels of spin-1 nuclei (such as 14N) by using multi-frequency excitation and a single RF coil. Experimental results on pure samples and mixtures are also presented.