Speaker
Description
This contribution focuses on nuclear beta decays occurring in highly ionized matter. Since the 1950s, several studies have investigated whether beta decay rates depend on the physical properties of the surrounding environment. While early experiments in high-pressure and high-temperature matter revealed only small variations—on the order of 3%—a dramatic change was later observed in the 1990s using Storage Rings, where decays of fully stripped or hydrogen-like ions were measured. For instance, the lifetime of 187Re, normally on the order of tens of gigayears, was found to collapse to only a few decades. This striking modification arises from a new decay channel known as Bound-State Beta Decay (BSBD). In this process, the emitted beta electron can be captured directly into an inner atomic orbital, altering the decay Q-value and phase-space configuration. As a result, the decay constant can increase dramatically, reducing the lifetime by many orders of magnitude. Beyond its intrinsic interest as a phenomenon at the intersection of atomic and nuclear physics, BSBD has significant implications for nuclear astrophysics. It affects the competition between neutron capture and beta decay in the s-process nucleosynthesis pathways that govern the production of heavy elements in stars. At INFN-LNS, a new facility named PANDORA is under construction to investigate, for the first time, BSBD and related effects within an Electron Cyclotron Resonance (ECR) plasma confined by a multimirror superconducting magnetic trap. The initial experimental program includes isotopes such as 94Nb, 176Lu, and 134Cs. In PANDORA, beta-decay lifetimes will be measured as a function of the electron temperature in a non-LTE plasma, where electrons reach energies of several tens of keV, while ions remain relatively cold (~eV).
In parallel, this contribution explores the potential of a future experiment employing a high-power, picosecond laser to generate plasmas under LTE conditions. Such an environment could enable the study of nuclear excitation—either direct or indirect, for example through Nuclear Excitation by Electron Capture (NEEC)—opening the way to unprecedented investigations of beta decay from excited nuclear matter. This scenario closely mirrors the conditions of astrophysical plasmas, offering a unique opportunity to simulate and understand the mechanisms of elemental nucleosynthesis in stellar environments