Dempster, Arthur Jeffrey, 1886-1950

<p>Arthur Jeffrey Dempster (August 14, 1886 – March 11, 1950) was a Canadian-American physicist best known for his work in mass spectrometry and his discovery in 1935 of the uranium isotope 235U. Dempster was born in Toronto, Ontario, Canada. He received his bachelor's and master's degrees at the University of Toronto in 1909 and 1910, respectively. He travelled to study in Germany, and then left at the outset of World War I for the United States; there he received his Ph.D. in physics at the University of Chicago.</p>
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Dempster joined the physics faculty at the University of Chicago in 1916 and remained there until his death in 1950. During World War II he worked on the secret Manhattan Project to develop the world's first nuclear weapons. From 1943 to 1946, Dempster was chief physicist of the University of Chicago's Metallurgical Laboratory or "Met Lab" which integrally related to the Manhattan Project and founded to study the materials necessary for the manufacture of atomic bombs. In 1946, he took a position as a division director at the Argonne National Laboratory. Dempster died on March 11, 1950 in Stuart, Florida at the age of 63.</p>

During his visit to Stanford University, in 1923, he met Germaine Collette, a Belgian scholar from the University of Liege, who was studying medieval literature at Stanford. Their friendship resulted in marriage in 1926. His wife, the holder of Ph.D. degrees from Liege and Stanford, continued her career beside him and has become an outstanding contributor to Chaucerian criticism. Her researches never failed to arouse the sympathetic interest of her husband, who greatly admired and appreciated her work.

Scientist. He was credited with the discovery of Uranium-238, a compound that was vital to the construction of the atom bomb. Attended the schools of the city of Toronto, Canada, excelled in his studies finishing in the top two of virtually every competition he entered. He attended the University of Toronto, graduating in 1909 with a bachelor's degree and in 1910 with a master's degree. By 1911 he had his first article published in the "Journal of the Royal Astronomical Society of Canada" and later in 1911 he went to Germany for additional and advanced studies spending three years in his pursuits. He attended the University of Munich and Gottingen, as well as the University of Wurzburg. Due to the beginning of World War I he was forced to leave Germany and enrolled at the University of Chicago in late 1914. By 1916 he received a doctorate in physics with the grade of summa cum laude, which at the time only one other student had achieved. He served with the Canadian Army Signal Corps during World War I and after the war returned to the University of Chicago, remaining there until his death. His work included the study of the properties of positive rays, or canal rays which were also described as positively charged atoms or molecules set into motion at high speed through the use of electric fields. His work and theories were thought to be a precursor of the modern mass spectrograph. His discovery of the element Uranium-238 would prove to be a key to the construction of the first atomic bomb during World War II. His contributions to physics were recognized by numerous awards including his election to the National Academy of Sciences in 1937, and in 1944 he became the President of the American Physical Society. He was regarded as the principal authority on positive rays and made extensive studies of the passage of protons thru helium, in which he made the discovery that protons go right thru helium without being appreciably deflected. At the time of his death he was Professor of Physics in the Division of the Physical Sciences of the University of Chicago, and Director of the Argonne National Laboratory's Division of Mass Spectroscopy and Crystallography.