BADGER, RICHARD MCLEAN

(b Elgin, Illinois, 4 May 1896; d. Pasadena, California. 26 November 1974)

physical chemistry, spectroscopy.

The son of Joseph Stillman Badger and Carrie Mabel Hewitt. Badger spent part of his youth in Brisbane, Australia, returning to Elgin to complete his secondary education. He attended Northwestern University (1916–1917), but his studies were interrupted by World War I, durum which he served in France in the 311th Field Signal Battalion. Demobilized in 1919, Badger resumed his college career at the California Institute of Technology. In 1921 he was awarded a bachelor’s degree in chemistry. His undergraduate thesis, “The Effect of Surface Conditions on the Intensity of X-ray Reflections from Crystal Planes,” was among the first studies completed at Caltech in what soon became the burgeoning field of X-ray crystallography.

After graduating, Badger remained at Caltech, working closely with Richard Chace Tolman and Arthur Amos Noyes. In 1924 he completed a dissertation on the free energy of formation of hydrogen cyanide and received his Ph.D. Although his dissertation reflected a new interest in chemical thermodynamics. Badger soon returned to the study of molecular structure, becoming an authority on the spectroscopic study of molecules in the infrared, visible, and ultraviolet regions. Aside from a year (1928–1929) as a National Research Council fellow at Göttingen and at Bonn, Badger spent his entire career at Caltech, where he was successively research fellow (1924–1928), assistant professor (1929–1938), associate professor (1938–1945), professor (1945–1966). and professor emeritus. He married Virginia Alice Sherman on 8 July 1933; they had two children. Anthony Sherman and Jennifer Hewitt.

Badger is best known as the author of “Badger’s rule,” an equation that relates the force and internuclear distance in a diatomic molecule. Formulated in 1933 on the basis of Badger’s empirical study of relevant data on diatomic molecules, the equation has the form

where r₁ is I he internuclear distance, k₁ is the force constant of the bond, and C_ij and d_ij are constants with values determined by the nature of the bonded atoms. Subsequent research by Badger and others showed that the equation is applicable to polyatomic as well as diatomic molecules. With the help of Badger’s rule, it became possible to calculate approximate values of interatomic distances within molecules from spectroscopic data alone. This was of considerable value in cases where interatomic distances could not be determined by electron diffraction experiments or other direct means.

Although Badger was alert to theoretical issues, he was primarily an experimentalist with a passion for spectroscopy. During the 1930’s and 1940’s, he and his students derived from their spectroscopic studies a wealth of information on the structure of such simple molecules as ethylene, ammonia, hydrogen cyanide, and ozone. Badger was among the first to use spectral data to determine values for internuclear distances, moments of inertia, and bond angles. Especially notable were his contributions to the study of the hydrogen bond. Here he used spectroscopic techniques to explore the conditions under which hydrogen bonds form and to study the contributions such bonds make to the stability of molecular structures. Badger’s experimental results constituted a valuable resource for his co-worker at Caltech, Linus Pauling.

After World War II, Badger extended his investigations to proteins and other large molecules. Although spectroscopic methods were inadequate to specify their structures, Badger found that spectral data were of some use in eliminating otherwise plausible configurations. During the postwar years Badger also made a number of improvements in the design of infrared spectrometers.

In 1952 Badger was elected to the National Academy of Sciences, and in 1961 he was awarded the Manufacturing Chemists’ Association Medal for excellence as a college chemistry teacher.

BIBLIOGRAPHY

I. Original Works. Budget published nearly one hundred scientific papers, many of which are listed in Poggendorff, Biographisch-literaisches Handwörterbuch, VIIb, 182–183. His most important writings are “A Relation Between Internuclear Distances and Bond Force Constants.” in Journal of Chemical Physics. 2 (1934), 128-131: “The Relation Between the Internuclear Distances and Force Constants of Molecules and Its Application to Polyatomic Molecules.” ibid., 3 (1935), 710–714; and “The Spectrum Characteristic of Hydrogen Bonds,” ibid., 5 (1937), 369–370, written with Simon H. Bauer.

II. Secondary Literature. There is a brief obituary in Engineering and Science. 38 (December 1974-January 1975), 24. A biographical memoir, with selected bibliography, is Oliver L. Wulf. “Richard McLean Badger,” in Biographical Memoirs. National Academy of Sciences. 56 (1987), 3–20.

John W. Servos