Peter Debye

Peter Debye carried out pioneering studies of molecular dipole moments, formulated theories of magnetic cooling and of electrolytic dissociation, and developed an X-ray diffraction technique for use with powdered, rather than crystallized, substances.

DebyeFor his work with dipole moments, the vector quantities related to the distribution of electric charges are measured in debyes. Also, in recognition of a number of his scientific contributions, Debye received the Nobel Prize in Chemistry in 1936.

A native of Maastricht, The Netherlands, Debye was born on March 24, 1884, as Petrus Josephus Wilhelmus Debije. His father worked in a machinery shop as a foreman. When Debye entered the Technische Hochschule in Aachen, Germany, the family finances were strained, but his father was determined to give him the best education possible. At the school, Debye met Arnold Sommerfeld, a renowned German theoretician who helped train many young scientists in the field of quantum physics. After Debye graduated in 1905 with a degree in electrical technology, Sommerfeld offered Debye, whom he would later describe as his greatest discovery, a position as assistant in his laboratory. During his time in Aachen, Debye enthusiastically researched a variety of topics, such as the diffraction of light by variously shaped objects and eddy currents. His study of eddy currents eventually resulted in his first published paper, which appeared in the Journal for Mathematics and Physics.

In 1906, Sommerfeld accepted a professorship at Ludwig-Maximilian University and Debye went with him to Munich in order to continue as his assistant. There Debye pursued a graduate degree, earning his Ph.D. in a few years. For his doctoral dissertation, Debye mathematically addressed the effects of radiation pressure. After graduation he stayed in Munich for another year as a physics lecturer.

Once Debye left Munich, he moved through a series of positions at several institutions. In 1911, he succeeded Albert Einstein as chair of theoretical physics at the University of Zürich. He worked there for only a year, but during this short time he began some of his most important work. By analyzing dipole moments, Debye discovered new information regarding the structure of a wide array of molecules.

Next, Debye moved back to The Netherlands to accept a professorship at Utrecht University. After two years, he relocated again, leaving his homeland for Germany and the University of Göttingen in 1914. By that time, Debye was married to Mathilde Alberer, one of the daughters of the owner of the boarding house where Debye resided in Munich. Eventually the couple would have two children. Their son, Peter Paul Ruprecht Debye, followed in his father’s footsteps and became a physicist. This made him a great help to the elder Debye, the two often collaborating in their research.

It was during his six years in Göttingen that Debye completed his work involving X-ray diffraction. Max von Laue, a colleague of Sommerfeld, had discovered that X- rays could be used to study the structure of materials in 1912, and William Henry Bragg and William Lawrence Bragg built upon the idea. Yet their work was hampered by the fact that their X-ray diffraction method of analysis necessitated that samples consist of sizable crystals, which were time consuming to prepare. Together with Paul Scherrer, Debye developed a way to use powdered samples in X-ray diffraction studies and examined many materials in this manner, which came to be called the Debye-Scherrer method.

In 1920, Debye became professor of physics and principal of the Swiss Federal Institute of Technology (ETH) in Zürich. In his new position Debye studied solutions of electrolytes, and with Erich Hückel extended the pioneering electrochemical work of Svante Arrhenius. The mathematical expression they developed to illuminate certain properties of electrolytes takes into consideration interionic interactions and is known as the Debye- Hückel equation. Also while at ETH, Debye discovered that the wavelength of X-rays increases when they collide with electrons. The phenomenon, which he described in 1923, is known as the Compton effect because, unbeknownst to Debye, it had been discovered a year earlier by American physicist Arthur Compton.

After seven years at ETH, Debye moved to the University of Leipzig to become head of the physics department. Then, in 1935, he accepted the directorship of the Kaiser Wilhelm Institute for Physics (later renamed the Max Planck Institute for Physics) and a professorship at the University of Berlin. While working in Berlin, Debye received the Nobel Prize in Chemistry “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.” Afterwards, the Nazi government told Debye he would have to become a German citizen to retain his post at the Institute. An unwilling Debye immigrated to Italy, but stayed only briefly before resettling in the United States.

Debye began a chemistry professorship at Cornell University in Ithaca, New York, in 1940. He remained with the university the rest of his career and acquired U.S. citizenship in 1946. After his official retirement in 1952, Debye frequently traveled to give lectures throughout the United States and Europe. In 1966, he experienced multiple heart attacks, leading to his death on November 2 of that year.