John Marshall returned to the Los Alamos Laboratory, while Leona, now effectively a single mother, became a fellow at the Institute for Advanced Study in Princeton, New Jersey in 1957. The following year she became a fellow at the Brookhaven National Laboratory, at a time when the focus of research in physics was shifting away from the nucleus and towards elementary particles.
John Marshall returned to his work at Los Alamos Laboratory, while Leona, now a solo parent, joined the Institute for Advanced Study in Princeton, New Jersey in 1957. The following year she became affiliated with Brookhaven National Laboratory, as physics research began to concentrate on elementary particles rather than atomic nuclei.