Contains correspondence; typescripts and manuscripts; scientific papers; research notes and mathematical calculations. Undated manuscript drafts of papers on nuclear physics, including an untitled paper on the compound nucleus. Collection of scientific papers (1950-1954) by others, dealing with research on atomic and molecular structures. Research notes and detailed algebraic calculations (probably circa 1950s but undated) concern Placzek's work on neutron scattering of crystals and the theory of Bose gases. Correspondence (1934-1952) both personal and professional, a portion of which details his interest in the study of Piero della Francesca's works on geometry at the Vatican, including a letter of recommendation to the conservator of the Vatican manuscripts, a description of the manuscripts, and reference notes. Correspondents include: Hans A. Bethe, Niels Bohr, Norris Bradbury, Subrahmanyan Chandrasekhar, Sir James Chadwick, Sir John Douglas Cockcroft, Enrico Fermi, Leopold Infeld, Kenneth Hay Kingdon, Arnold N. Lowan, Robert Eugene Marshak, Robert Green Sachs, Chauncey Guy Suits, Richard C. Tolman, George Volkoff, Philip Wallace, Gian Carlo Wick, Eugene Wigner, Chen Ning Yang.