We study a two-level quantum system embedded in a dispersive environment and coupled with the electromagnetic field. We expand the theory of light-matter interactions to include the spatial extension of the system, taken into account through its wavefunctions. This is a development beyond the point-dipole approximation. This ingredient enables us to overcome the divergence problem related to the Green tensor propagator. Hence, we can reformulate the expressions for the spontaneous emission rate and the Lamb shift. In particular, the inclusion of the spatial structure of the atomic system clarifies the role of the asymmetry of atomic states with respect to spatial inversion in these quantities.

中文翻译：

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与色散介质中扩展量子系统的光相互作用

我们研究了嵌入在色散环境中并与电磁场耦合的两级量子系统。我们扩展了光-物质相互作用的理论，以包括系统的空间扩展，通过其波函数加以考虑。这是超越点偶极子近似的发展。这种成分使我们能够克服与绿色张量传播器相关的发散问题。因此，我们可以重新表述自发辐射率和兰姆位移的表达式。特别是，包含原子系统的空间结构阐明了原子状态的不对称性相对于这些量的空间反转的作用。