Complex sentence: Raimond enrolled at the École normale supérieure (rue d'Ulm) (ENS) in 1975, his first research workds after a DEA in atomic and molecular physics was about superradiance and Rydberg atoms.
Split into simpler sentences: Raimond enrolled at the École normale supérieure (rue d'Ulm) (ENS) in 1975. After graduating with a DEA in atomic and molecular physics, his first research work was in superradiance and Rydberg atoms.