PREcision Studies with Optically pumped Beams of Exotic Nuclei

Projektbeschreibung

Forschung bringt Licht ins Dunkel der Neutronenverteilung in instabilen Atomkernen

Neutronen geben wichtige Einblicke in die Struktur des Atomkerns, aber als ungeladene Teilchen entziehen sie sich Messungen über ihre Verteilung um den Nukleus. Jedoch hilft ihr magnetisches Moment weitgehend bei der Charakterisierung der Verteilung des magnetischen Moments von Atomkernen. Das EU-finanzierte Projekt PRESOBEN nutzt neue experimentelle Ansätze, um herauszufinden, wie Neutronen die magnetischen Momente instabiler Atomkerne bestimmen. Auf der Grundlage erfolgreicher Arbeiten in einem früheren Projekt werden die Forschenden kurzlebige Kerne durch die Kombination von kernmagnetischer Resonanz und Zweistrahlspektroskopie untersuchen. Die enge Zusammenarbeit mit Atom- und Kernforschungsgruppen wird es ermöglichen, die Magnetisierung und die Neutronenverteilung (Struktur der Neutronenhalos) in vielen leichten und schweren Kernen zu bestimmen, darunter 11Be, Ne, Na, Mg, K und Ca.

Ziel

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. I 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 in my team, allowing to determine magnetic moments of unstable nuclei up to ppm accuracy. I will combine this approach with accurate measurements of the hyperfine structure using the laser-rf double-resonance. The signals will be detected efficiently using decay anisotropy, 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 11Be, proposed halos in neutron-rich Ne, Na, Mg, K, and Ca nuclei, and heavy Rn, Fr, and Ra isotopes, interesting for studies of atomic parity violation (APV) and electric dipole moments. The project will take place at the ISOLDE facility at CERN. I 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 test of atomic and nuclear calculations.