Shortly after receipt of his doctorate in 1935, Maier-Leibnitz became an assistant to Walther Bothe, Director of the Institut für Physik (Institute for Physics) of the Kaiser-Wilhelm Institut für medizinische Forschung (KWImF, Kaiser Wilhelm Institute for Medical Research), in Heidelberg. [Note: After World War II, the KWImF was renamed the Max-Planck Institut für medizinische Forschung. In 1958, Bothe's Institut für Physik was spun off and elevated to become the Max-Planck-Institut für Kernphysik (MPIK, Max Planck Institute for Nuclear Physics).] Bothe had first met Maier-Leibnitz while on a recruiting trip to the University of Göttingen during which Robert Pohl and Georg Joos highly recommended Maier-Leibnitz for his intelligence and creativity. Maier-Leibnitz arrived at the Institute for Physics shortly after the arrival of Wolfgang Gentner, who became recognized as Bothe's second in command and took Maier-Leibnitz under his wing to become his mentor, critic, and a close friend. Maier-Leibnitz worked on nuclear spectroscopy, electron-gamma-ray coincidence measurements, radioactive tracers, and energy conservation in Compton scattering.