Billion-Fold Enhancement in Sensitivity of Nuclear Magnetic Resonance Spectroscopy for Magnesium Ions in Solution

β‐nuclear magnetic resonance (NMR) spectroscopy is highly sensitive compared to conventional NMR spectroscopy, and may be applied for several elements across the periodic table. β‐NMR has previously been successfully applied in the fields of nuclear and solid‐state physics. In this work, β‐NMR is applied, for the first time, to record an NMR spectrum for a species in solution. 31Mg β‐NMR spectra are measured for as few as 107 magnesium ions in ionic liquid (EMIM‐Ac) within minutes, as a prototypical test case. Resonances are observed at 3882.9 and 3887.2 kHz in an external field of 0.3 T. The key achievement of the current work is to demonstrate that β‐NMR is applicable for the analysis of species in solution, and thus represents a novel spectroscopic technique for use in general chemistry and potentially in biochemistry. Highly sensitive: 31Mg β‐NMR spectra are measured for as few as 107 magnesium ions in ionic liquid (EMIM‐Ac), in an external field of 0.3 T, as a prototypical test case (left). The experimental setup (right) includes an incoming nuclear‐spin‐polarized 31Mg+ ion beam, a sample (indicated as a drop), β‐particle scintillation detectors, and an NMR magnet.