Pionium is investigated in various pion-pion strong interactions which reproduce well the pion-pion scattering data. It is found that the ground-state pionium wave functions in those realistic pion-pion strong interactions are considerably different from the hydrogen-like one at small distance. One may suggest that some pion-pion interactions may need to be largely improved before applied to the pion-pion atomic system. © 2007 Elsevier B.V. All rights reserved.
Yan, Y., Suebka, P., Kobdaj, C., & Khosonthongkee, K. (2007). Strong interactions in pionium. Nuclear Physics A, 790(1–4), 402–405. https://doi.org/10.1016/j.nuclphysa.2007.03.071