The German Physicist Otto Stern He was born on February 17, 1888 in Sorau, Upper Silesia. In 1906 he entered the University of Breslau, completing his doctorate in physical chemistry in 1912. He then went to the University of Prague to study with Albert Einstein and, when the latter moved to the Swiss Federal Institute of Technology (FIT) in Zurich, Stern He followed it up, becoming a professor at the FIT in 1913.
The next year, Stern he accepted a similar position in theoretical physics at the University of Frankfurt am Main, but was almost immediately called up for military service. After the war and a brief stint at the University of Berlin in 1918, he returned to Frankfurt. There, moving from theory to experiment, he conceived and carried out the first of the experiments with atomic and molecular beams that earned him an international reputation and, ultimately, the Nobel Prize in 1943.
Stern discovered that electrons rotating around the nucleus of an atom had “orbital angular momentum” and produced a magnetic moment along the axis of rotation. This magnetic moment gave rise to a magnetic field identical to that established by a small bar magnet located on the axis of rotation of the electron. Therefore, if a bundle of atoms, each with a magnetic moment, were sent through a non-uniform external magnetic field, each atom would experience a net force, the magnitude of which would depend on the orientation of the atom’s magnetic moment, with respect to to the direction of the external magnetic field.
In classical theory, all orientations of the atom’s magnetic moment are possible, so the external field must deflect as many atoms both above and below the original direction of the beam, causing them to simply scatter. Instead, using a beam of silver atoms, Stern and Walter Gerlach discovered that the beam divided into two separate beams, one above and the other below the original direction. This observation completely contradicted classical theory; showed that not all the orientations of the magnetic moment of the atom were possible; that is, it showed the existence of the “spatial quantization“.
In later years, both as a professor at Frankfurt and as a full professor at Rostock and Hamburg, or (after fleeing Nazi persecution) as a research professor of physics at the Carnegie Institute of Technology in Pittsburgh, where he remained from 1933 to 1945, Stern he devised a series of different experiments that took advantage of the atomic and molecular beam technique that he had developed. For example, he checked the accuracy of the Maxwell-Boltzmann velocity distribution in gas molecules; measured the nuclear magnetic moments and the magnetic moment of the proton; finally, he observed the wave nature of helium and hydrogen atoms by diffracting the beams of these atoms.
In 1945, the same year he retired and took up residence in Berkeley, California, Stern he was elected to the National Academy of Sciences, one of the many honors he received during the course of his life. He died in Berkeley on August 17, 1969.