Nuclear Physics Consolidated Grant 2020

More than a century since Rutherford identified the atomic nucleus in alpha-particle scattering experiments in Manchester, the science of nuclear physics remains vibrant and active. Over the past 100 years, there has been a wealth of experimental and theoretical research that has led to milestone results and discoveries, such as the discovery of the neutron, the development of successful models of the nucleus, and the identification of numerous novel decay modes. Progress in nuclear physics has gone hand-in-hand with the development of particle accelerators, which started with modest electrostatic machines, capable of accelerating light ions, and resulting in modern day accelerators capable of accelerating any nucleus up to uranium-238, with energies of 10 MeV per nucleon or more. Facilities now exist that can accelerate radioactive ions, and there is effort being put into improving the intensities, energies, and purity of radioactive beams. Despite the wealth of research activity in nuclear physics, and the maturity of the subject, a complete understanding of the atomic nucleus has still not been achieved. There are still many open questions that need to be answered, which we will address is our research programme. Also, technological and scientific developments in nuclear physics are leading to applications outside of the areas of fundamental science - nuclear-related concepts are now used in many areas of industry and medicine, leading to additional areas of research. Our programme of research in this Consolidated Grant application covers research into the structure, behaviour and properties of atomic nuclei that lie far from stability as well as collective behaviour in stable nuclei, which remains poorly understood.

One of the main parts of our programme of research is the study of the shapes of atomic nuclei. It is well established that nuclei with filled shells of neutrons and protons are spherical, and nuclei with partially-filled shells can become deformed. One of the themes within our research programme will study quadrupole shaped nuclei, where the nucleus takes on a rugby-ball shape. This type of nuclear deformation is prevalent and occurs in many different regions of the nuclear chart. A more exotic form of deformation is when the nucleus takes on a reflection-asymmetric "pear" shape. Such octupole deformation is most prominent in localized regions of the nuclear chart, such as the light actinide region (radium, thorium, uranium nuclei with A~224) and lanthanides near barium-144. In our research programme, we will make a comprehensive study of octupole deformation in nuclei, focusing on the actinide and lanthanide regions, as well as the proton-rich nuclei near N=Z=56. Interestingly, atoms containing pear-shaped nuclei are excellent candidates in which to search for matter-antimatter symmetry violating physics.

Over the past 20 years, experimental observations, supported by theoretical calculations, have suggested that the structure of exotic nuclei may be different from those near stability. The well-known sequence of magic numbers, corresponding to energy gaps in nuclear shell structure, is now thought to change in nuclei that lie far from stability. In our programme, we will study the shell structure in a range of nuclei across the nuclear chart, including the nuclei close to the doubly-magic nuclei Sn-100 and Pb-208. Another aspect of our research programme is a study of high-energy collective modes in nuclei, in novel experiments induced by beams of gamma rays. In addition, a new aspect to our research is a study of reactions relevant to nuclear astrophysics, which will include a focus on hydrogen burning that occurs in stars.