Natural abundance O17 and S33 nuclear magnetic resonance spectroscopy in solids achieved through extended coherence lifetimes

• Published in: Physical review. B 2019-10, Vol.100 (14)
• Main Authors: Jardón-Álvarez, Daniel, Bovee, Mark O, Baltisberger, Jay H, Grandinetti, Philip J
• Format: Article
• Language: English
• Subjects: Coherence; Field strength; NMR; Nuclear magnetic resonance; Nuclei; Potassium sulfate; Quartz; Sensitivity enhancement; Spectrum analysis; Spin-lattice relaxation
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.100.140103

We have found that the NMR coherence lifetime T2 of the symmetric central ±12→∓12 transition for O17 nuclei through a π pulse train can be extended by over two orders of magnitude in a lattice dilute with NMR active nuclei through the use of highly selective (low-power) radio-frequency pulses. Crucial to this lifetime extension is the avoidance of coherence transfer to short-lived nonsymmetric transitions. For O17 in α-quartz, we obtain T2=262±1s. This translates into enormous sensitivity gains for echo train acquisition schemes such as Carr-Purcell-Meiboom-Gill (CPMG). By combining satellite population transfer schemes with a low-power (2.73 kHz) CPMG on O17 in quartz, we obtain over a 1000-fold sensitivity enhancement compared to a spectrum from a free induction decay acquired at a more typical rf field strength of 32.5kHz. For S33 in K2SO4 the same approach yields T2=8.8±0.4s and a sensitivity enhancement of 63. In both examples, these enhancements enable the acquisition of NMR spectra at 9.4 T, despite their low natural abundance and spin-lattice relaxation times of ∼900 and 25s, respectively, with signal-to-noise ratios of ∼30 in 1 h.