We study theoretically the structure of double pionic atoms, in which two negatively charged pions ($\pi^-$) are bound in the atomic orbits. The double pionic atom is considered to be an interesting system from the point of view of the multi-bosonic systems. In addition, it could be possible to deduce valuable information on the isospin $I = 2$$\pi\pi$ interaction and the pion–nucleus strong interaction. In this paper, we take into account the $\pi\pi$ strong and electromagnetic interactions, and evaluate the effects on the binding energies by perturbation theory for the double pionic atoms in heavy nuclei. We investigate several combinations of two pionic states and find that the order of magnitude of the energy shifts due to the $\pi\pi$ interaction is around 10 keV for the strong interaction and around 100 keV for the electromagnetic interaction for the ground states.

中文翻译：

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双离子原子的结构

我们从理论上研究了双介子原子的结构，其中两个带负电的介子（$\pi^-$）被束缚在原子轨道上。从多玻色子系统的角度来看，双介子原子被认为是一个有趣的系统。此外，还可以推断出关于同位旋 $I = 2$$\pi\pi$ 相互作用和介子-核强相互作用的有价值的信息。在本文中，我们考虑了$\pi\pi$强相互作用和电磁相互作用，并通过微扰理论评估了重核中双pionic原子对结合能的影响。