After he received his PhD in physics from Princeton University in 1916, Compton continued research at the University of Minnesota and at the Cavendish Laboratory at the University of Cambridge England.
In a paper presented to the AAAS in 1920 and published in the Journal of the Franklin Institute for August 1921, Compton not only asserted the electron is the elementary magnetic particle but also that its spin is quantized and may be the cause of the unexplained gyromagnetic anomaly found by Steward and Barnett.
Arthur Compton discovered that the wavelength of x-rays changes when they are elastically scattered by electrons, a phenomenon generally known as the Compton Effect.
He found that the rays would be divided into two lines or wavelengths, one line would be of one and the same wavelengths as the incident radiation, and the other would be the scattered rays of a longer wavelength.
Discovery of Compton Effect by Arthur Holly Compton