Joey Pomperada

Elec 424-81

3/4/03

Debye Peter Joseph William Debye, a Dutch-American chemical physicist, was one of the most renowned scientists of the modern world. His developments in the concepts of polar molecules, methods for studying chemical substances with x-rays, and the Debye-

Huckel theory has paved the way for future discoveries in physics, chemistry, and electrical engineering.

Debye was born with the name Petrus Josephus Wilhelmus Debije to Joannes

Wilhelmus Debije and Maria Ruemkens, on March 28, 1884 in Maastrict, the

Netherlands. He is better known by the Anglicized form of his name, Peter Joseph

William (or Wilhelm) Debye. His father worked as a foreman at a metal ware manufacturer, and his mother was a theater cashier. He also had a younger sister.

For his primary and secondary education, Debye attended the Hoogere Burger

School in Maastricht from 1896 to 1901. At seventeen years old he enrolled at the

Technische Hochschule in Aachen, across the Dutch-German border. Debye completed his undergraduate studies at Aachen and received his degree in electrical engineering in

1905 (Biography Resource Center).

One of Debye's teachers at Aachen was the great German physicist Arnold

Sommerfeld. In 1906, Debye joined Sommerfield as an assistant when Sommerfield was called to the chair of the theoretical physics at the University of Münich. Debye earned his doctorate in physics in 1908, and he continued his research there until 1911. His thesis was on the subject of radiation and its effects on spherical particles with a variety of refractive properties. In his final year there, he served as a lecturer in physics.

In 1911, Debye was offered a chair of theoretical physics at the University of

Zürich. This was especially impressive because Albert Einstein previously held this position. During his year at the University, Debye studied the dipole moment of molecules. The dipole moment is a molecule’s tendency to rotate in an external magnetic field: a property that is a function of the distribution of electric charge in the molecule.

In 1912, Debye continued his research on the dipole of molecules at the

University of Utrecht. By 1914, Debye took a position at the University of Göttingen as professor of theoretical and experimental physics. It was at this University where he conducted his most important work: studying x-ray diffraction. The use of x-rays to determine the structure of materials had been developed only a few years earlier by Max

Laue and by William Henry Bragg and William Lawrence Bragg. Debye, working with a colleague named Paul Scherrer, discovered that x-ray diffraction could also be used with powders. This solved the most serious problem with the Laue-Bragg discoveries, which was that x-ray diffraction required the preparation of relatively large crystals (Britannica).

Debye returned to the University of Zürich in 1920 where he worked as professor of experimental physics and director of the physics laboratory at the Federal Institute of

Technology (Macmillan). During his tenure at Zürich, Debye developed the theory of electrolytic dissociation with another colleague, Erich Hückel. The Swedish chemist

Svante Arrhenius made new discoveries on the behavior of electrolytes, substances that conduct electricity through the movement of ions, in the late 1880s. Arrhenius had argued that molecules break up spontaneously in solution, with the liberated ions becoming electrolytic agents. Debye found a different approach to the problem by way of redefining the mathematical application to physicochemical data, instead of to each possible configuration of ions (Britannica). He proposed that electrolytes must dissociate almost completely in solution because they are already completely ionic in the solid state. He added that the reason they do not behave as a solid in a solution is that each ion has become surrounded by other ions of opposite charge. The movement of ions through a solution is disturbed by the dragging effect of the surrounding ions. Working with

Hückel, Debye generated a mathematical theory that precisely described the behavior of electrolytes in solution (Encyclopedia Americana). In 1923, Debye also developed a theory that mathematically explained the Compton effect - the way the wavelengths of x- rays change when they collide with electrons - and provided additional support for the wave-particle theory of electromagnetic radiation. He continued these studies when he moved to the University of Leipzig from 1927 to 1934 and then to the University of

Berlin in 1934.

Debye received the Nobel Prize in chemistry in 1936 for his contributions to physics, chemistry, and quantum mechanics, including "his contributions to our knowledge of molecular structure through the investigations of dipole moments and on the diffraction of x rays and electrons in gases" (The Nobel Foundation).

In Germany, the rise of National Socialism caused an increase of political issues in German research. Debye was soon required to become a German citizen in order to retain his position in Berlin. He decided to accept an appointment as professor of chemistry and head of the department at Cornell University in Ithaca, New York, in 1940 and became a U.S. citizen by 1946. Debye officially retired from his duties at Cornell in

1952, but he continued his research in the field of polymer chemistry for another decade.

During this time, Debye was much in demand as a lecturer, both in the United Sates and

Europe, and remained active in the scientific community until the age of 81(Macmillan).

Debye died of a heart attack, on November 2, 1966, at his home in Ithaca. Peter Debye is perhaps best known for his contribution to the theory of electrolytic dissociation, the Debye-Hückel theory, announced in 1923. Most of Peter

Debye's professional work involved the application of physical laws to the structure and behavior of molecules. In the 1910s, he determined the dipole moments of many molecules, obtaining results that allowed him to calculate the polarity of such molecules.

In recognition of this work, the unit of dipole moment, the Debye, was named in his honor (Biography Resource Center).

During his lifetime, Debye received many honors and awards. Debye was awarded the 1936 Nobel Prize in chemistry for this research. He also received the

Rumford Medal of the Royal Society in 1930, the Lorentz Medal of the Royal

Netherlands Academy of Sciences in 1935, the Franklin Medal of the Franklin Institute in

1937, the Faraday Medal in 1949, the Gibbs Medal in 1949, the Kendall Award in 1957, the Nichols Medal in 1963, and the Priestley Medal of the American Chemical Society in

1963. Bibliography

Prock McKonkey. Topics in Chemical Physics. New York: El Sevier Publishing Company, 1962.

Harkins, William D. The Physical Chemistry of Surface Films. New York: Reinhold Publishing Corporation, 1952.

“Peter Debye – Biography.” Nobel e-Museum: The Official Web Site of The Nobel Foundation. 2002. The Nobel Foundation. http://www.nobel.se/chemistry/laureates/1936/debye-bio.html.

Macmillan Encyclopedia of Chemistry. New York: Simon & Schuster and Prentice Hall International, 1997, Vol. 2. “Debye, Peter (1184-1966).” p. 457.

The Encyclopedia Americana: International Edition. Danbury, CT: Grolis Inc., 1999, Vol. 8. “Debye.” p. 582

The New Encyclopedia Britannica. Chicago, Illinois: Encyclopedia Britannica Inc., 2002, Vol. 3. “Debye, Peter.” p. 946-947.

“Peter Debye – Biographical Essay.” Biography Resource Center. 2001. Daniel Library, The Citadel – DISCUS http://library- cat.citadel.edu:2056/servlet/BioRC?ste=4&AI=131732&NA=Debye&vrsn=2.0&ca =1&tbst=prp&srchtp=name&n=10&locID=thecitadel&OP=contains.