%0 Journal Article
%A Süfke, Martin
%A Lehmkuhl, Sören
%A Liebisch, Alexander
%A Blümich, Bernhard
%A Appelt, Stephan
%T Para-hydrogen raser delivers sub-millihertz resolution in nuclear magnetic resonance
%J Nature physics
%V 13
%@ 1745-2481
%C Basingstoke
%I Nature Publishing Group
%M FZJ-2017-02612
%P 568–572
%D 2017
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000402604200017
%R 10.1038/nphys4076
%U https://juser.fz-juelich.de/record/828746