  Atoms constitute relatively simple many-body systems, making them suitable
objects for developing an understanding of basic aspects of many-body physics.
Photoabsorption spectroscopy is a prominent method to study the electronic
structure of atoms and the inherent many-body interactions. In this article the
impact of many-body effects on well-known spectroscopic features such as
Rydberg series, Fano resonances, Cooper minima, and giant resonances is
studied, and related many-body phenomena in other fields are outlined. To
calculate photoabsorption cross sections the time-dependent configuration
interaction singles (TDCIS) model is employed. The conceptual clearness of
TDCIS in combination with the compactness of atomic systems allows for a
pedagogical introduction to many-body phenomena.

Atomic Physics