Beta-detected NMR is up to 10 orders of magnitude more sensitive than conventional NMR, because it is based on the detection of beta-particles from hyperpolarized short-lived nuclei. Our project aims at applying it for the first time to liquid samples relevant in chemistry and biology, thus extending its use from nuclear structure and material science studies in solid environments.
Our experimental setup, built in 2016 and upgraded in 2017 and 2018, is located at the CERN-ISOLDE facility, where over 1000 different radioactive nuclei can be produced. We use optical pumping with lasers on isotopes of different metallic elements, resulting in nuclear polarizations up to 90%. The decrease in the anisotropic emission of beta radiation from such nuclei is then used to detect the NMR response, leading to the extreme sensitivity of beta-NMR.
First studies on 26Na in liquid samples were performed by us in 2017, which lead to much narrower beta-NMR resonances than seen previously in solid hosts. Thanks to the shimming and active stabilisation of our 1.2 T electromagnet at the 1 ppm level, in 2018 we could determine the magnetic moments of several short-lived Na nuclei with about 100 times improved precision. This provides a self-consistent set of nuclei to be used in beta-NMR studies in liquid samples, connected to the moment of stable 23Na. In 2018 we furthermore probed the interaction of Na cations with DNA G-quadruplex stuructures, present e.g. in telomeres. Present upgrades to the experimental setup should allow to apply this approach to isotopes of more chemical elements (e.g. K, Cu or Zn) in an even broader range of research topics, such as alkali-metal batteries.
This contribution will introduce the technique and describe the experimental setup, and will concentrate on the most recent results in physics and biology, followed by a short outlook.