Peter Joseph William Debye (March 24, 1884 - November 2, 1966) (born Petrus Josephus Wilhelmus Debije) was a Dutch-American physical chemist.
Peter "Pie" Debye was born in Maastricht and after attending local schools in Maastricht went to the University of Aachen, Germany, only 30 km from Maastricht, in 1901. He studied mathematics and classical physics, and in 1905 received a degree in electrical engineering. In 1907 he published his first paper, a mathematically elegant solution of a problem involving eddy currents. At Aachen he studied under the theoretical physicist Arnold Sommerfeld, who later claimed that his most important discovery was Peter Debye.
In 1906, Sommerfeld received an appointment at Munich, and took Debye with him as his assistant. He got his Ph. D. with a dissertation on radiation pressure in 1908. In 1910 he derived the Planck radiation formula using a method which Max Planck agreed was simpler than his own method.
In 1911, when Albert Einstein took an appointment as a professor at Prague, Debye took his old professorship at Zürich. This was followed by moves to Utrecht in 1912, Göttingen in 1913, back to Zürich in 1920, to Leipzig in 1927, and to Berlin in 1934, where he became director of the Kaiser Wilhelm Institute, saw to the construction of new laboratories, and developed it into the now-world-regarded Max Planck Institute in 1938.
In 1913 he married Mathilde Alberer. They had a son and a daughter; their son (Peter P. Debye) became a physicist and collaborated with Debye in some of his researches.
Scientific contributions prior to the Nobel Prize
His first major scientific contribution was the application of the concept of dipole moment to the charge distribution in asymmetric molecules in 1912, developing equations relating dipole moments to temperature, dielectric constant, etc. In consequence, molecular dipole moments are measured in debyes, a unit named in his honor.
Also in 1912, he extended Albert Einstein's theory of specific heat to lower temperatures by including contributions from low-frequency phonons. See Debye model.
in 1913, he extended Niels Bohr's theory of atomic structure, introducing elliptical orbits, a concept also introduced by Arnold Sommerfeld.
In 1914-1915, he calculated the effect of temperature on X-ray diffraction patterns of crystalline solids with Paul Scherrer.
In 1923, with his assistant Erich Hückel, he developed an improvement of Svante Arrhenius' theory of electrical conductivity in electrolytic solutions. Although an improvement was made to the Debye-Hückel equation in 1926 by Lars Onsager, the theory is still regarded as a major forward step in our understanding of electrolytic solutions.
Also in 1923, he developed a theory to explain the Compton effect, the shifting of the frequency of X-rays when they interact with electrons.
His Nobel Prize
In 1936, Debye was awarded the Nobel Prize in Chemistry "for his contributions to the study of molecular structure," primarily referring to his work on dipole moments and X-ray diffraction.
In 1938 the Nazi government began to insist that Debye give up his Dutch citizenship and become a German citizen. Debye did not want to do so, and since he had been offered a chance to give a series of lectures at Cornell University in Ithaca, New York, traveled to the United States of America. He ended up staying at Cornell, became a professor (and, for 10 years, chairman of the chemistry department) there, and in 1946 became an American citizen. Unlike the European phase of his life, where Debye moved from city to city every few years, in the United States he remained at Cornell for the whole remainder of his career. He retired in 1952, but continued research until his death.
Much of his work at Cornell concerned the use of light-scattering techniques (derived from his X-ray scattering work of years earlier) to determine the size and molecular weight of polymer molecules. This started as a result of his work during World War II on synthetic rubber, but was extended to proteins and other macromolecules.
In April 1966 he suffered a heart attack, and in November of that year a second, which proved fatal.
In plasma physics, the phenomenon known as Debye shielding, where a plasma shields out an electro-static field, is named after him.