Gerhard Herzberg

German-born Canadian physicist

• Born: December 25, 1904
• Birthplace: Hamburg, Germany
• Died: March 3, 1999
• Place of death: Ottawa, Ontario, Canada

Herzberg became the leading researcher in the spectroscopy of atoms and molecules at a time when rapid development of the quantum theory made it possible to explain the observed spectra in terms of the behavior of the electrons and nuclei involved. Over the course of a productive career, Herzberg made many measurements of significance for chemistry and astronomy.

Early Life

Gerhard Herzberg (GAYR-hahrt HEHRZ-behrg) was born in a suburb of Hamburg, the second son of Albin and Ella Herzberg. The Herzbergs were a prosperous Protestant family that could afford to enroll Gerhard and his brother, Walter, in a highly respected Vorschule (elementary school). Herzberg’s father died in 1915, shortly before his son’s graduation. Herzberg then moved to Frankfurt to live with an aunt and uncle and attend high school to prepare for a teaching career, but he was unhappy in Frankfurt and returned to Hamburg. He attended the Realgymnasium of the Johanneum, a college preparatory school specializing in science and mathematics.

As was the case for many German families, the Herzberg boys and their mother suffered financially during the hyperinflation that followed the defeat of Germany in World War I. In 1922, Ella Herzberg left Germany for Seattle, Washington, where she married the son of a friend. She would send a little money back to her sons from time to time.

By 1924, Herzberg had passed the all-important Arbitur exam and gained admission to the Technical University of Darmstadt. Unfortunately, the small income Herzberg obtained by tutoring and from his mother was too small to provide both living expenses and tuition. He was able to obtain a scholarship from a private company for the first two years and a scholarship from a foundation for the next two. He graduated from Darmstadt with the Doktor Inginieur degree in 1928. He then spent a period working with Max Born and James Franck at the University of Göttingen and at the University of Bristol in England. He completed the habilitation requirement at Darmstadt in 1929 and was admitted to the faculty as a Privatdocent, an unsalaried lecturer. In the meantime he had met a physics student, Luise Oettinger, at Göttingen; they married in 1929. Oettinger continued her education for the doctorate degree and would become one of Herzberg’s most valued collaborators.

Life’s Work

Herzberg’s doctoral research would prove to be a good indicator of his scientific interests and working characteristics. Originally, working under Professor Hans Rau, he had planned to study the emission spectrum of doubly ionized lithium atoms, which theory predicted would resemble the hydrogen atom spectrum. For this purpose he sealed a small amount of lithium vapor in an evacuated tube through which an electrical current could be passed to excite the lithium to emit light. Herzberg noticed, though, that there was a brief yellow afterglow following the passage of current and decided to investigate this instead.

What Herzberg found was that this afterglow was actually an emission of light from the nitrogen molecules that had been left in the tube. He then measured and analyzed the emission spectrum of the diatomic nitrogen molecule instead, which involved far more challenging experimental and theoretical work. He would continue to study the spectra of molecules throughout his career. In 1929, working with Walter Heitler, he published an analysis of the nitrogen spectrum that suggested the existence of a new particle, the neutron, in the nucleus.

Over the next few years the Nazi Party rose to power in Germany. At first, Herzberg was not worried about his university position he was not Jewish, and while his wife came from a Jewish family, she was the daughter of a war veteran. By the time Herzberg began actively seeking a position outside Germany, however, the exodus of German scientists was well under way, and there were few open jobs. At Göttingen, Herzberg had served as sponsor to John Spinks at the University of Saskatchewan in Saskatoon, Canada. Herzberg chose this rather remote campus as his next career stop. The university’s president, Walter C. Murray, was determined to establish a stronger research institution and agreed to Herzberg’s appointment as research professor. With the outbreak of World War II, Herzberg technically became an enemy alien in Canada, but this had little effect on his work. He even contributed to the Canadian war effort by developing spectroscopic methods that could be used to study the chemistry of explosions. Residents of Saskatoon became used to the sound of occasional explosions, as Herzberg developed spectroscopic methods that could follow the course of the chemical reactions occurring there.

While the Herzbergs had a comfortable living situation at Saskatoon, they were anxious to work in a more challenging scientific environment. Herzberg had long had an interest in astronomy, and in 1945 he secured a position as associate professor of astronomy and later professor of spectroscopy at the Yerkes Observatory of the University of Chicago, located at Williams Bay, Wisconsin. Herzberg’s new position allowed him to make some fundamental contributions to astronomy, including the identification of a number of molecular species in interstellar space. The observatory was not in cosmopolitan Chicago but at a site chosen for its remoteness from light pollution. Herzberg missed the cultural life of a university town and decided to return to Canada.

Fortunately, the Canadian government decided to make a major investment in scientific research as a means of supporting the development of industry in Canada following the war. A centerpiece of this effort, managed by the National Research Council (NRC) of Canada, was the establishment of a limited number of laboratories for pure scientific research. In 1948, Herzberg became senior research officer in the Division of Physics of the NRC at Ottawa, where he would be free to build bigger spectroscopes and hire the best young scientific talent to help him in research of his own choosing. He became director of the division a year later. Thus began an extended period of high research productivity that would continue until his official retirement in 1994.

Herzberg published more than 250 scientific papers and five books, which were translated into several languages. Awards and accolades included dozens of honorary doctorates, election to the prestigious Royal Society of London in 1951, the presidency of the Royal Society of Canada in 1966, the Faraday Medal in 1970, and the Royal Medal of the Royal Society of London and the Nobel Prize in Chemistry in 1971. He was named chancellor of Carleton University in Ottawa in 1973 but continued his research, publishing his final scientific paper in 1996.

Significance

Scientific study of the solar spectrum began with the classic prism experiment of Isaac Newton in 1664. By 1814, German physicist Joseph von Fraunhofer was able to show the presence of hundreds of missing wavelengths, or “dark lines,” in the spectrum. By the late 1850’s Germans Gustav Kirchhoff and Robert Bunsen demonstrated that the dark lines were the result of absorption of specific wavelengths by elements present in the solar atmosphere, the same wavelengths that would be emitted by the elements when heated. A basis for understanding the emission and absorption spectra of atoms was provided by the quantum theory developed in the mid 1920’s.

Herzberg began his scientific career when careful spectroscopic measurements were needed to confirm the predictions of quantum theory and to explain the motions of electrons and nuclei in the states allowed by quantum mechanics. Obtaining accurate spectra presented a constant sequence of technical challenges. Herzberg remained in the forefront of spectrometer design, often being the first to obtain the spectra of highly unstable and short-lived species.

Several generations of chemists and atomic and molecular physicists are acquainted with Herzberg primarily from his five published volumes, one on atomic spectra, three on molecules and one on free radicals, all models of clear scientific exposition and still valuable as reference works.

Bibliography

Herzberg, Gerhard. “Molecular Spectroscopy: A Personal History.” In Annual Review of Physical Chemistry 36 (1985): 1-30. Edited by B. S. Rabinovitch, J. M. Schurr, and H. L. Strauss. Herzberg reflects on his scientific career.

‗‗‗‗‗‗‗. Spectra and Structures of Simple Free Radicals: An Introduction to Molecular Spectroscopy. New York: Dover, 2003. Originally published in 1971, this book provides Herzberg’s own introduction to the field that occupied him through most of his career.

Stoicheff, Boris. Gerhard Herzberg: An Illustrious Life in Science. Ottowa, Ont.: National Research Council Press, 2002. The only full-length biography in English, written by a scientific collaborator. This work also provides much information on the development of science in Canada after World War II. Comprehensive at more than four hundred pages.