Neutrons are fascinating particles and are important for nuclear structure, tests of the standard model of particle physics, or properties of neutron stars. Unfortunately, they are electrically neutral, so learning about their distribution in nuclei, especially far from stability, is difficult. However, they possess a magnetic moment, which contributes to –and sometimes dominates– the distribution of nuclear magnetization. This project aims to address the challenging question of the distribution of magnetisation and neutrons in unstable nuclei. We will use a novel, high-accuracy experimental approach, combining radiation-detected Nuclear Magnetic Resonance with rf-laser double spectroscopy on optically-pumped short-lived nuclei. The project builds on recent achievements, allowing to determine magnetic moments of unstable nuclei up to ppm accuracy. We will combine this approach with accurate measurements of the hyperfine structure using the laser-rf double-resonance. The signals will be detected efficiently using anisotropy in beta or gamma decay, thanks to spin polarisation via optical pumping. This will lead to an accurate determination of a ‘hyperfine anomaly’, a small effect on atomic hyperfine structure due to the distribution of nuclear magnetisation. A close collaboration with atomic and nuclear theorists will allow to determine the magnetisation and neutron distribution in many nuclei: light neutron-halo beryllium-11, proposed halos in neutron-rich neon, sodium, magnesium, potassium and calcium, and heavy radon, francium, and radium isotopes, interesting for studies of atomic parity violation (APV) and electric dipole moments. The project will take place at the ISOLDE facility at CERN. We will also work closely with quantum-chemistry, atomic- and nuclear-physics theorists, who will use our data to improve their approaches. This will open new perspectives for nuclear structure studies, determination of neutron-star properties, or APV studies. It will also allow tests of atomic and nuclear calculations.
