text: Franck married Hertha Sponer in a civil ceremony on 29 June 1946, his first wife, Ingrid, having died in 1942. In his post-war research, he continued to tackle the problem of explaining the mechanism of photosynthesis. Meitner saw no break between his early and later work. She recalled that
  In addition to the Nobel Prize. Franck was awarded the Max Planck medal of the Deutsche Physikalische Gesellschaft in 1951 and the Rumford Medal of the American Academy of Arts and Sciences for his work on photosynthesis in 1955. He became an honorary citizen of Göttingen in 1953, was elected a member of the United States National Academy of Sciences in 1944, and elected a Foreign Member of the Royal Society (ForMemRS) in 1964. He was also an International Member of the American Philosophical Society.
  He died suddenly from a heart attack while visiting Göttingen on 21 May 1964, and was buried in Chicago with his first wife.
  In 1967, the University of Chicago named the James Franck Institute after him. A lunar crater has also been named in his honour. His papers are in the University of Chicago Library.