Quantum & Fundamental Physics The research program of the Atomic, Quantum & Fundamental Physics group at GSI takes advantage of the unique possibilities arising from the availability of intense beams of highly [...] with atomic physics methods The workhorse of the Atomic, Quantum & Fundamental Physics department at GSI is the ESR. In the ESR, highly-charged ions can be stored and investigated over a long period of time [...] beam or during collisions with hydrogen atoms from a gas jet is investigated, to mention only two examples. Important information about the electronic structure of ions can be obtained from the measured