Systematic studies of the continuum-coupling correlations in near-threshold states

par David Cardona (GANIL)

jeudi 12 nov. 2026, 14:00 → 15:00 Europe/Paris

100/2-A201 - Salle A201 (IJCLab)

Nuclei are open quantum systems: their particle-emission thresholds lie low in their own excitation spectra, so most of their states are resonances, and the continuum these decay into belongs to the same Hamiltonian rather than to an external environment. This work studies what the coupling to that continuum does to light nuclei, where the thresholds are densely interleaved with the levels and the systems are still small enough to be treated microscopically using the Gamow Shell Model.

 

In this approach nuclear states are built from a mix of different configurations of the nucleons in their single-particle orbits. Which configurations dominate depends on how close a state lies to the decay channels available to it, and on the other states around it. This work takes up both. First we take a doublet of equal angular momentum and parity and drive their mixing through their shared continuum until the two states become indistinguishable and coalesce into one, a so-called exceptional point. In its proximity the individual states stop being meaningful objects, the reaction cross sections depart from the usual resonance shapes, and the decay is no longer exponential. Then, in ⁴He we follow several states across the available thresholds, each gaining binding and shifting the weight of its configuration towards the channel that opens near it, a direct microscopic demonstration of near-threshold clustering.