TY  - JOUR
AU  - Süfke, Martin
AU  - Lehmkuhl, Sören
AU  - Liebisch, Alexander
AU  - Blümich, Bernhard
AU  - Appelt, Stephan
TI  - Para-hydrogen raser delivers sub-millihertz resolution in nuclear magnetic resonance
JO  - Nature physics
VL  - 13
SN  - 1745-2481
CY  - Basingstoke
PB  - Nature Publishing Group
M1  - FZJ-2017-02612
SP  - 568–572
PY  - 2017
AB  - The precision of nuclear magnetic resonance spectroscopy1 (NMR) is limited by the signal-to-noise ratio, the measurement time Tm and the linewidth Δν = 1/(πT2). Overcoming the T 2 limit is possible if the nuclear spins of a molecule emit continuous radio waves. Lasers and masers are self-organized systems which emit coherent radiation in the optical and micro-wave regime. Both are based on creating a population inversion of specific energy states. Here we show continuous oscillations of proton spins of organic molecules in the radiofrequency regime (raser5). We achieve this by coupling a population inversion created through signal amplification by reversible exchange (SABRE) to a high-quality-factor resonator. For the case of 15N labelled molecules, we observe multi-mode raser activity, which reports different spin quantum states. The corresponding 1H-15N J-coupled NMR spectra exhibit unprecedented sub-millihertz resolution and can be explained assuming two-spin ordered quantum states. Our findings demonstrate a substantial improvement in the frequency resolution of NMR.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000402604200017
DO  - DOI:10.1038/nphys4076
UR  - https://juser.fz-juelich.de/record/828746
ER  -