|Vol. XXXIV, No. 1||April, 2001|
(1912 - 2001)
By Mitio Inokuti
|With the passing of Ugo Fano on 13 February
2001, the Radiation Research Society lost an influential founding member. A broader
community dearly misses a great theoretical physicist.
Ugo Fano was born to Rosa Cassin and Gino Fano (1871-1952), professor of mathematics at Turin, Italy, specializing in differential geometry. Having studied mathematics first at the University of Turin, the younger Fano turned to physics under the influence of his cousin, Giulio Racah (1909-1965), a physicist known for the powerful theory of angular momentum. Then Fano was fortunate to receive postdoctoral training from two giants in modern physics: Enrico Fermi at Rome in 1934-1936 and Werner Heisenberg at Leipzig in 1936-1937.
In 1939 Fano married Camilla ("Lilla") Lattes, who not only kept a comfortable home but also collaborated with Fano in science and worked as a teacher for many years. In the same year the couple emigrated to the United States. Fanos American career began with pioneering work in 1940-1944 in what was later to be called radiation biology with M. Demerec and others, at the Department of Genetics of the Carnegie Institution at Cold Spring Harbor. It is noteworthy that, after a seminar in Rome by P. Jordan on x-ray effects on genetic material, Fermi had suggested to Fano that the biological action of radiation would be an important and suitable topic for study. Fanos papers in this period concerned chromosomal rearrangements, mutations, lethal effects, and genetic effects of X-rays and neutrons on Drosophila melanogaster, as well as theoretical analysis of genetic data. His work also included the discovery of bacteriophage-resistant mutants in Escherichia coli, following up earlier studies by Salvador E. Luria, also a native of Turin, whom Fano had introduced to Fermis group and who received the Nobel Prize in 1969 together with Max Delbrück and Alfred D. Hershey.
After a wartime effort at the U.S. Army Ballistic Research Laboratory in 1944-1945, Fano joined the staff of the National Bureau of Standards (NBS, the predecessor of the National Institute of Standards and Technology) in 1946, initially as a member of the radiological physics group led by Lauriston S. Taylor. Fanos two decades at NBS saw prolific and outstanding contributions to two major areas of research: radiation physics and the basic physics of atoms, molecules, and condensed matter.
Many of Fanos contributions to radiation physics are seminal to later developments. In 1946 he put forth the first general theory of the yield of ionization in a gas. In 1947 he pointed out the statistical fluctuations of ionization and characterized them by what is now known as the Fano factor. In 1951-1959 he led L.V. Spencer, M.J. Berger, and others in developing methods for treating the transport of photons and charged particles in matter. The invention in 1953-1954 of the degradation spectrum for characterizing electrons and other charged particles in matter was especially influential. In 1954, Fano also demonstrated the cavity principle of radiation equilibrium under general conditions. In later years at Chicago, he maintained a keen interest in radiation physics and studied topics such as the behavior of slow electrons in condensed matter, which are produced abundantly by any ionizing radiation.
Fanos work after the mid 1950s focused increasingly on basic and microscopic aspects of radiation interactions with matter, including condensed-phase effects on radiation absorption (studied in 1956-1960) and stopping powers of materials (comprehensively reviewed in 1963). Thus, Fano identified the oscillator-strength spectrum over the entire range of excitation energies as a key property of any material, characterizing its interaction with radiation. At the same time, recognizing the severe limitations of the photon sources in the far ultraviolet and soft X-ray domains then available, Fano saw that photons emitted from an electron synchrotron were eminently suitable. Thus, he encouraged R.P. Madden and co-workers at NBS to use synchrotron radiation for spectroscopic studies, which led to fruitful results important not only to radiation physics but also to the basic physics of atoms, molecules, and condensed matter. Later, he continued for many years to campaign for the use of synchrotron radiation, for which numerous facilities have now been developed worldwide.
The numerous, wide-ranging influences of Fano in basic physics and chemistry grew mostly from his years since 1965 at The University of Chicago. Not only did he train approximately 30 Ph.D. students and many postdoctoral fellows, but he communicated regularly with scientists around the world in meetings or by telephone calls, letters, and electronic mail, liberally sharing his ideas and incisive insights into scientific matters. This style of "doing physics" (in Fanos frequently used words) stems from Fermi, who strove to see the essence of knowledge in experimental facts and to tell it to others in simple and unpretentious words. We shall continue to learn much from his five monographs and over 250 papers.
Understandably, Fano was recognized with many honors, including the Enrico Fermi Award by the U.S. Government, membership in the National Academy of Science of the United States, a foreign membership in the Royal Society of London, and membership in the Accademia Nazionale dei Lincei, as well as honorary doctorates from Université Pierre et Marie Curie and The Queens University of Belfast.
In concluding this tribute, I take the liberty of citing this lesson of Fanos that I often heard: "Lets make radiation research not only useful for the public but also respectable in the eyes of basic scientists."
For the reader who may wish to obtain further information, a forthcoming issue of Physics Essays in honor of Fano will contain his curriculum vitae, a list of his publications, a biographical essay, and 40 articles reporting on recent developments in science topics he investigated. In addition, the same issue carries his last article, "The Memories of an Atomic Physicist for My Children and Grandchildren."
The above article was prepared by Dr. Mitio Inokuti (Physics Division, Argonne National Laboratory, Argonne, Illinois 60439) for publication in Radiation Research. Work was supported in part by the U.S. Department of Energy, Office of Science, Nuclear Physics Division, under Contract No. W-31-109-Eng-38.
Readers may also be interested in visiting the following websites for more on Dr. Fano: