Abstract
Nuclear Magnetic Resonance (NMR) is an intriguing quantum‐mechanical effect that is used for routine medical diagnostics and chemical analysis alike. Numerous advancements have contributed to the success of the technique, including hyperpolarized contrast agents that enable real‐time imaging of metabolism in vivo. Herein, we report the finding of an NMR radio amplification by stimulated emission of radiation (RASER), which continuously emits 1H NMR signal for more than 10 min. Using parahydrogen induced hyperpolarization (PHIP) with 50 % para‐hydrogen, we demonstrated the effect at 600 MHz but expect that it is functional across a wide range of frequencies, e.g. 101–103 MHz. PHIP‐RASER occurs spontaneously or can be triggered with a standard NMR excitation. Full chemical shift resolution was maintained, and a linewidth of 0.6 ppb was achieved. The effect was reproduced by simulations using a weakly coupled, two spin‐1/2 system. All devices used were standard issue, such that the effect can be reproduced by any NMR lab worldwide with access to liquid nitrogen for producing parahydrogen.
Highlights
A 400 MHz RASER was enabled by Dissolution Dynamic Nuclear Polarization[6,7], only for a single shot experiment: RASER signal bursts were observed for 3 seconds after a hyperpolarized sample was poured into a cavity.[8]
Closest to the high frequency continuous emission was likely a 129Xe RASER, where 11, 139 MHz bursts were observed at 11.7 T for 8.5 min
Süfke et al.[10] demonstrated a continuous Nuclear Magnetic Resonance (NMR) RASER based on an ingenious combination of innovative hardware[11] and Signal Amplification By Reversible exchange[12] (SABRE): SABRERASER.[13]
Summary
Experiments were carried out on a 600 MHz spectrometer (Bruker Avance II) with a cryogenically cooled probe (TCI) with Q=v/ Δv ≅600.2 MHz/1.2 MHz ≅ 500 (see SI, Fig. S3) and 5 mm screw-cap NMR tubes (Wilmad). Continuous PHIP-RASER emission (Fig. 1B) was composed of 13 FID’s of 1153844 points which corresponded to an acquisition time of 60 s per single FID. These FIDs were acquired sequentially with 1-3 s delay between experiments, this time was required for the spectrometer to load and start new acquisition. 2. NMR spectra acquired during and without pH2 bubbling (supplementary to Fig 1) Figure S2. It follows that Q=v0/Δv1/2 ≅600 MHz / 1.2 MHz ≅ 500
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