The Nuclear Physics Division of the European Physical Society (EPS) is delighted to announce that the winner of the 2022 Lise Meitner prize is Prof. Phil Walker (University of Surrey). The prize is given every two years for outstanding work in the fields of experimental, theoretical or applied nuclear science and Prof. Walker has been awarded the prize for seminal contributions to the understanding of long-lived nuclear excited “isomeric” states and the factors that determine their half-lives, that range from nanoseconds to years.

Since their discovery by Otto Hahn 100 years ago, isomers have been a cornerstone of our understanding of nuclear structure. These long-lived nuclear excited states give access to the basic physics of both the collective and the individual-nucleon behaviour of nuclei, together with important applications in diverse areas including astrophysics, medical imaging, Mössbauer spectroscopy, time keeping, coherent gamma-ray emission, and energy storage. Walker’s research has a strong focus on the basic properties of isomers, and how these might be exploited for energy applications. He has led the way in recognising and developing novel techniques for revealing isomer structures. For example, in his early work Walker used gamma-ray spectroscopy with pulsed beams to establish some of the most isomer-rich structures in hafnium (Z=72) and tantalum (Z=73) isotopes. Walker worked on isomer theory to predict the existence of some exceptional long-lived isomers in neutron-rich isotopes of the same elements. Although out of experimental reach at the time, such isomers could later be studied, as proposed and led by Walker, using projectile-fragmentation reactions to inject isomers into the new and unique heavy-ion storage ring at GSI in Germany. The new isomers discovered by this method could themselves be revealed in more detail following deep-inelastic reactions and exploiting a new design of isotope separator at RIKEN in Japan. Key experiments have been proposed and led by Walker. This latter work is ongoing, with important results already published.

A controversial aspect of research into nuclear isomers is the possibility that their energy-storage capability could be exploited and, crucially, that it might be possible to release the stored energy in a controlled manner. The high energy density of isomers (≈1 MeV per atom, compared to chemical energies ≈1 eV per atom) could lead to dramatic applications. Walker has been a keen advocate of the science challenges in this area, requiring research at the interface between atomic physics, plasma physics and nuclear physics. New and exciting opportunities are being opened up at FAIR, FRIB and other next-generation radioactive-beam facilities.

Prof. Walker has made outstanding developments in the study and understanding of isomeric states  including critical insights into possible isomer applications, such as energy storage and coherent gamma-ray emission. He has also led in the development and exploitation of a range of experimental techniques, from low-energy isotope separators to high-energy storage rings, which will also extend the isomer research opportunities with the new generation of radioactive-beam facilities.

More info

• Press release from the University of Surrey
• EPS NPD Lise Meitner Prize for Nuclear Science