SCHERRER, PAUL HERMANN

(b. St. Gall, Switzerland, 3 February 1890; d. Zurich, Switzerland, 25 September 1969)

physics, physical chemistry.

After Scherrer completed the compulsory portion of his education, it was decided that he should have commercial training. He therefore entered the Eidgenössische Handels-und Verkehrsschule in St. Gall. He was soon attracted by the natural sciences, however, and in 1908 entered the Eidgenössische Technische Hochschule (ETH) in Zurich, At first his main field of study was botany, but after a year he changed to mathematics and physics. In 1912 Scherrer decided to become a physicist and went to the University of Königsberg for one semester. The following year he transferred to Göttingen, a famous center of mathematics and physics.

At Göttingen, Scherrer became a promising physicist under the influence of Peter Debye, Woldemar Voigt, and Hermann T. Simon. World War I forced him to interrupt his studies at Göttingen in order to do his military service in Switzerland. In early 1916 Scherrer completed his doctoral dissertation, on the Faraday effect of hydrogen molecules; it was accepted, and he received the doctorate summa cum laude.

Two years later Scherrer became a Privatdozent with a Hahilitationsschrif that dealt with the determination of the size and structure of very small colloidal particles, a subject related to the colloidal research being conducted at Göttingen under the leadership of Richard A. Zsigmondy. But while Zsigmondy and other researchers investigated colloidal particles with the ultramicroscope, Scherrer applied the X-ray method that the he had recently developed with Debye. In this way Scherrer contributed greatly to the new science of colloids, investigating organic colloids with X rays, he was the first to observe the fiborus struture of cellulose and other organic compounds.

Scherrer’s most important work was the invention of the X-ray technique for studying the structure of polycrystalline materials. The initiative seems to have come from Debye, who in 1915 proposed to Scherrer that they study diffraction effects of monochromatic X rays. After an unsuccessful attempt using paper and charcoal as scattering substances, Scherrer constructed a new X-ray diffraction device with a cylindrical camera. Using this apparatus, in December 1915 Debye and Scherrer found a series of sharp lines arising from X-ray diffraction in lithium fluoride powder. The result was contrary to Debye’s expectations, but Debye and Scherrer soon provided the accepted interpretation: that the lines are due to diffraction from the randomly oriented micro crystals.

In subsequent experiments Debye and Scherrer saw X-ray diffraction effects in fluids. They studied benzene and cyclohexane and showed that the diffraction diagrams yield information about the molecular structure of liquids.

Other collaborative work by Scherrer and Debye dealt with the structure of graphite, diamond, and various ionic crystals. In 1918 they determined what is now called the atomic form factor of lithium fluoride. They argued from the X-ray diffraction diagram that lithium fluoride consists of singly ionized atoms (Li⁺F⁻), a result not obvious at the time. The DebyeScherrer method in X-ray analysis soon developed into an important branch of physics and also proved to have industrial applications. A very similar method was independently invented in 1917 by Albert W. Hull, who worked for General Electric.

Debye was appointed professor at the ETH in 1920, and Scherrer followed him a few months later as professor of experimental physics. In 1927, when Debye went to Leipzig, Scherrer became director of the ETH Institute of Physics. First with Debye and later with Wolfgang Pauli (who in 1928 succeeded Debye), Scherrer made ETH a physics center of international reputation. He was professor at ETH until his retirement in 1960. After retiring he lectured regularly at the University of Basel.

In Zurich, Scherrer at first continued his work with X-ray analysis. In 1922 he determined the structure of various complex salts and proved they were in accordance with the ideas of Alfred Werner, which were based on chemical reasoning. Scherrer soon turned to other subjects that he found more promising. In the 1920’s he dealt with ferroelectrics, magnetism, piezoelectricity, and other aspects of solid-state physics. When the atomic nucleus became a fashionable subject of study in the late 1920’s, Scherrer was quick to start a research program in nuclear physics. Through his dynamic leadership and astute sense of fruitful research areas, ETH became a major center for nuclear and solid-state physics in the 1930’s.

Scberrer’s contribution to ETH, and to European physics in general, was not limited to his scientific discoveries. He was an excellent organizer and teacher, and devoted much of his time to these activities. One of his talents was his ability to raise funds for science. Scherrer realized that modern experimental physics was big science, and succeeded in attracting money and talent to ETH. After World War II he became interested in nuclear energy. He was active in the foundation of the European Center for Nuclear Research (CERN) and served as president of the Swiss Nuclear Energy Commission.

Scherrer put his stamp on Swiss physics not least through his teaching. He was an enthusiastic teacher with many devoted pupils. His lectures included perfected demonstration experiments and a considerable element of showmanship that made them attractive to nonphysicists.

BIBLIOGRAPHY

I. Original Works. “Interferenzen an regellos orientierten Teilcben in Röntgenlicht”, in Nachichten der Kgl. Gesellschaft der Wissenschaften su Göttingen (1916), 1-26, written with Peter Debye—also published under the same title in Physikalische Zeitschrift, 17 (1916), 277-283, and 18 (1917), 291-301; “Bestimmung der Grösse und der inneren Struktur von Kolloidteilchen mittels Röntgenstrahlen”, in Nachrichten der Kgl Gesellschaft de Wissenschaftern zu Göttingen (1918), 98-100; “Atombau”, in Physikalische Zeitschrift, 19 (1918), 474-483, written with Peter Debye; “Bestimmung der von Werner abgeleiteten Struktur anorganischen Verbindungen vermittelst Röntgenstrahlen”, in Zeitschrift für anorganische und allgemeine Chemie, 121 (1922), 319-320, written with P. Stoll. See also his “Personal Reminiscences” in P. Ewald, ed., Fifty Years of X-Ray Diffraction (Utrecht, 1962), 641-646.

II. Secondary Literature. Hans Frauenfelder, Oskar Huber, and Peter Stähelin, eds., Beiträge zur Entwicklung der Physik: Festgabe zum 70. Geburtstag von Professor Paul Scherrer (Basel, 1960), See also Hans Frauenfelder and Rolf M. Steffen, “Paul Scherrer: Directed Swiss Physics Institute”, in Physics Today, 23 (January 1970), 129-133; P. Huber. “Prof. Dr. Paul Scherrer (1890-1969)”, in Helvetica physica acta, 23 (1950), 5-8; and J. Weigle introduction to the Festheft for Scherrer’s sixtieth birthday, ibid., 23 (1950), 4-5.

Helge Kragh