The main contribution of the Dutch-born American physical chemist Peter Joseph William Debye (1884-1966) was the development of methods based on induced dipole moments and X-ray diffraction for the investigation of molecular structures.

Peter Debye was born on March 24, 1884, in Maastricht, Netherlands, the son of William and Maria Reumkens Debije. At the age of 17 Debye entered the Technical Institute of Aachen and earned his diploma in electrical engineering in 1905. He immediately obtained the position of assistant in technical mechanics at the institute. At the same time his interest in physics received strong promptings from Arthur Sommerfeld, then serving on the faculty. Debye followed Sommerfeld to the University of Munich and obtained his doctorate in physics by a mathematical analysis of the pressure of radiation on spheres of arbitrary electrical properties.

The dissertation and a 1907 paper on Foucault currents in rectangular conductors gave clear evidence of Debye's ability to produce the mathematical tools demanded by his topics. A fitting recognition of Debye's youthful excellence was his succession in 1911, at the age of 27, to Albert Einstein in the chair of theoretical physics at the University of Zurich. While in Zurich he worked out, on the basis of Max Planck's and Einstein's ideas, the first complete theory of the specific heat of solids and the equally important theory of polar molecules. Debye was professor of theoretical physics at the University of Utrecht from 1912 until 1914, when he received the prestigious post of director of the theoretical branch of the Institute of Physics at the University of Göttingen. In 1915 he became editor of the famed Physikalische Zeitschrift and served in that capacity for 25 years.

X-ray Research

In Göttingen, Debye started a most fruitful collaboration with P. Scherrer. Their first paper, "X-ray Interference Patterns of Particles Oriented at Random" (1916), gave immediate evidence of the enormous potentialities of their powder method to explore the structure of crystals with very high symmetry. It also proved very useful in work with polycrystalline metals and colloidal systems. Two years later Debye and Scherrer extended the method from the study of the coordination of atoms to the arrangement of electrons inside the atom. It was in this connection that they formulated the important concept of "atomic form factor." Debye and Scherrer formed such a close team that when, in 1920, Debye became professor of experimental physics and director of the physics laboratory at the Swiss Federal Technical Institute in Zurich, Scherrer followed him there. The two inaugurated a most influential X-ray research center which attracted students from all over the world.

In the field of X-ray research Debye's signal success in Zurich was his demonstration in early 1923 that in the collision between X-rays and electrons, energy and momentum are conserved; he also suggested that the interaction between electromagnetic radiation and electrons must therefore be considered as a collision between photons and electrons. But Debye's principal achievement in Zurich consisted in the formulation of his theories of magnetic cooling and of interionic attraction in electrolyte solutions. The latter work, in which he collaborated with E. Hückel, was closely related to Debye's pioneering research on dipole moments. Debye had already been for 2 years the director of the Physical Institute at the University of Leipzig when his classic monograph, Polar Molecules, was published in 1928.

War and Postwar Years

Debye's rather rapid moves from one university to another were motivated by his eagerness to work with the best available experimental apparatus. Thus in 1934 he readily accepted the invitation of the University of Berlin to serve both as professor at the university and as director of the Kaiser Wilhelm Institute. The latter establishment, now known as Max Planck Institute, was just completing, with the help of the Rockefeller Foundation, a new laboratory which was to represent the best of its kind on the Continent. During his stay in Berlin, Debye became the recipient of the Nobel Prize in chemistry for 1936. It was awarded to him "for his contributions to our knowledge of molecular structure through his investigations on dipole moments and on the diffraction of x-rays and electrons in gases."

Meanwhile, the Nazi government began to renege on its original promise that Debye would not be asked to renounce his Dutch citizenship while serving as director of the Kaiser Wilhelm Institute, a post with a lifetime tenure. Shortly after World War II broke out, he was informed that he could no longer enter the laboratory of the Institute unless he assumed German citizenship. As Debye refused, he was told to stay home and keep busy writing books. He succeeded in making his way to Italy and from there to Cornell University, which invited him to give the Baker Lectures in 1940.

Debye made Cornell his permanent home. He served there as head of the chemistry department for the next 10 years. His wartime service to his adopted country (he became a citizen of the United States in 1946) concerned the synthetic rubber program. In pure research he further investigated, in collaboration with his son, Peter P. Debye, the light-scattering properties of polymers, on which he based the now generally accepted absolute determination of their molecular weights. He was a member of all leading scientific societies and the recipient of all major awards in chemistry. His outgoing personality kept generating enthusiasm and goodwill throughout his long life, which came to an end on Nov. 2, 1966. Since 1913 he had been married to Mathilde Alberer, who shared his lively interest in gardening and fishing.

Further Reading

• The best sources available on Debye's life and on the various aspects of his scientific work are the introductory essays in The Collected Papers of Peter J. W. Debye (1954). A detailed biographical profile of Debye is in the Royal Society, Biographical Memoirs of Fellows of the Royal Society, vol. 16 (1970). Debye is discussed in Eduard Farber, Nobel Prize Winners in Chemistry, 1901-1961 (1953; rev. ed. 1963); Aaron I. Ihde, The Development of Modern Chemistry (1964); and Chemistry: Nobel Lectures, Including Presentation Speeches and Laureates' Biographies, 1922-41, published by the Nobel Foundation (1966).