Arthur Jeffrey Dempster

Arthur Jeffrey Dempster

Canadian-American physicist, member of the US National Academy of Sciences
Date of Birth: 14.08.1886
Country: Canada

Content:
  1. Arthur Dempster: Pioneer in Mass Spectrometry and Isotope Discovery
  2. Career in Germany and the Invention of the Mass Spectrometer
  3. The First Mass Spectrometer and Isotope Discovery
  4. Further Advances in Mass Spectrometry
  5. Discovery of Uranium-235
  6. Later Years and Legacy

Arthur Dempster: Pioneer in Mass Spectrometry and Isotope Discovery

Early Life and Education

Arthur Dempster, a Canadian-American physicist, was born on August 14, 1886, in Toronto, Canada, to James and Emily Dempster. He earned degrees in physics and mathematics from the University of Toronto, graduating with a bachelor's degree in 1909 and a master's degree in 1910.

Career in Germany and the Invention of the Mass Spectrometer

In 1911, Dempster traveled to Germany and studied at the universities of Munich, Göttingen, and Würzburg. At the University of Würzburg under Wilhelm Wien, he conducted research on the deflection of positive ions in electric and magnetic fields, which laid the groundwork for his later invention of the mass spectrometer.

The First Mass Spectrometer and Isotope Discovery

Returning to the United States in 1914, Dempster joined the University of Chicago. In 1918, he built the first mass spectrograph, an instrument that could separate isotopes based on their mass-to-charge ratio. This groundbreaking invention revolutionized the field of mass spectrometry and enabled Dempster to discover numerous stable isotopes of various elements, including magnesium, calcium, platinum, palladium, barium, tellurium, tungsten, and gadolinium.

Further Advances in Mass Spectrometry

In 1936, Dempster collaborated with Kenneth Bainbridge and Josef Mattauch to develop a double-focusing mass spectrograph, which provided higher precision and accuracy in isotopic analysis. In 1928, he refined Aston's packing fraction curve, which describes the relationship between the mass and atomic number of elements.

Discovery of Uranium-235

Dempster's most significant discovery came in 1935 when he identified the uranium-235 isotope. This unstable isotope is essential for nuclear energy and weapons production.

Later Years and Legacy

Dempster continued his research at the University of Chicago until his death in 1950. He was elected President of the American Physical Society in 1944 and was a member of the National Academy of Sciences. Dempster's contributions to mass spectrometry and isotope research have had a profound impact on science and technology. He is regarded as a pioneer in these fields and his work has paved the way for numerous advancements in physics, chemistry, and nuclear science.

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