Arthur Jeffrey Dempster | |
|---|---|
 Dempster, c. 1925-30 | |
| Born | August 14, 1886 |
| Died | March 11, 1950(1950-03-11) (aged 63) Stuart, Florida, U.S. |
| Nationality | Canadian-American |
| Alma mater | B.S.University of Toronto M.S.University of Toronto Ph.D.University of Chicago |
| Known for | Developed the first modern mass spectrometer, discovered235U (the fissile isotope of uranium) |
| Awards | Newcomb Cleveland Prize(1929) |
| Scientific career | |
| Fields | Physics |
| External videos | |
|---|---|
 | |
 Michael A. Grayson,Discovery of Isotopes of Elements (Part I: Arthur Jeffrey Dempster), Profiles in Chemistry,Chemical Heritage Foundation |
Arthur Jeffrey Dempster (August 14, 1886 – March 11, 1950)[1][2] was a Canadian-Americanphysicist best known for his work inmass spectrometry and his discovery in 1935 of theuraniumisotope235U.[3] As part of his research, he investigated the isotopic constitution of multiple other elements.
Dempster was born inToronto, Ontario, Canada. He received hisbachelor's andmaster's degrees at theUniversity of Toronto in 1909 and 1910, respectively. After spending a semester each at Gottingen and Munich, Germany, and two years at the University of Wurzburg under Wilhelm Wien he left at the outset ofWorld War I for the United States; there he completed hisPh.D. in physics, graduating summa cum laude, at theUniversity of Chicago originally begun in Germany under Wien.
Dempster joined thephysics faculty at the University of Chicago in 1916 and remained there until his death in 1950. He co-developed a double-focusing mass spectrograph in 1936 with the help of the Americans Kenneth T. Bainbridge and J.H.E. Mattauch of Austria. This apparatus allowed the measurement of the mass of atomic nuclei.
DuringWorld War II he worked on the secretManhattan Project to develop the world's firstatomic bomb.
Dempster used a mass spectrometer of his design, in 1935 to find uranium-235, an isotope of uranium which is lighter than uranium-238. The quantity of uranium-235 in naturally occurring uranium is only 0.7%.
Dempster was elected to theAmerican Philosophical Society in 1932 and the United StatesNational Academy of Sciences in 1937.
From 1943 to 1946, Dempster was chief physicist of the University of Chicago'sMetallurgical Laboratory or "Met Lab" which integrally related to the Manhattan Project and was founded to study the materials necessary for the manufacture of atomic bombs.
In 1946, he took a position as a division director at theArgonne National Laboratory.
Dempster died on March 11, 1950, inStuart, Florida, at the age of 63 of a myocardial infarction whilst on vacation.
In 1918, Dempster developed the first modernmass spectrometer, a scientific apparatus allowing physicists to identify compounds by the mass of elements in a sample, and determine the isotopic composition of elements in a sample.[4] Dempster's mass spectrometer was over 100 times more accurate than previous versions, and established the basic theory and design of mass spectrometers that is still used to this day. Dempster's research over his career centered on the mass spectrometer and its applications, leading in 1935 to his discovery of thefissile uranium isotope235U.[3] Dempster was also well known as an authority onpositive rays.
| International | |
|---|---|
| National | |
| Other | |
