American Philosophical Society
Member History

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Residency
Resident (1)
Class
1. Mathematical and Physical Sciences[X]
Subdivision
106. Physics (1)
1Name:  Dr. Val L. Fitch
 Institution:  Princeton University
 Year Elected:  1995
 Class:  1. Mathematical and Physical Sciences
 Subdivision:  106. Physics
 Residency:  Resident
 Living? :   Deceased
 Birth Date:  1923
 Death Date:  February 5, 2015
   
 
Val L. Fitch was born the youngest of three children on a cattle ranch in Cherry County, Nebraska, not far from the South Dakota border: a very sparsely populated part of the United States and remote from any center of population. His family later moved to Gordon, Nebraska, a town about 25 miles away, where all of his formal schooling took place. The most significant occurrence in his education, however, came when, as a soldier in the U.S. Army in WWII, he was sent to Los Alamos, New Mexico, to work on the Manhattan Project. Under the direction of Ernest Titterton, a member of the British Mission, he was engaged in highly stimulating work while, even as a technician garbed in a military fatigue uniform, he had the opportunity to meet and see at work many of the great figures in physics: Fermi, Bohr, Chadwick, Rabi, Tolman, etc. Dr. Fitch recorded some of the experiences from those days in a chapter in All in Our Time, a book edited by Jane Wilson and published by the Bulletin of Atomic Scientists. All told, he spent three years at Los Alamos and in that period learned well the techniques of experimental physics. He observed that the most accomplished experimentalists were also the ones who knew the most about electronics, so electronic techniques were the first he learned. But mainly he learned, in approaching the measurement of new phenomena, not just to consider using existing apparatus but to allow the mind to wander freely and invent new ways of doing the job. Robert Bacher, the leader of the physics division in which he worked, offered Dr. Fitch a graduate assistantship at Cornell after the war, but he still had to finish the work for an undergraduate degree, which he did at McGill University. Another opportunity for graduate work soon came from Columbia, and he ended up there working with for his Ph.D. thesis. One day in his office, which he shared at the time with Aage Bohr, Rainwater handed him a preprint of a paper by John Wheeler devoted to µ-mesic atoms. This paper emphasized, in the case of the heavier nuclei, the extreme sensitivity of the Is level to the size of the nucleus. Even though the radiation from these atoms had never been observed, these atomic systems might be a good thesis topic. At this same time a convergence of technical developments took place. The Columbia Nevis cyclotron was just coming into operation. The beams of (pi)-measons from the cyclotron contained an admixture of µ-measons which came from the decay of the (pi)'s and which could be separated by range. Sodium iodide with thallium activation had just been shown by Hofstadter to be an excellent scintillation counter and energy spectrometer for gamma rays. And there were new phototubes just being produced by RCA which were suitable matches to sodium iodide crystals to convert the scintillations to electrical signals. The other essential ingredient to make a gamma-ray spectrometer was a multichannel pulse height analyzer which, utilizing his Los Alamos experience, Dr. Fitch designed and built with the aid of a technician. The net result of all the effort for his thesis was the pioneering work on µ-mesic atoms. It is of interest to note that the group came very close to missing the observation of the gamma-rays completely. Wheeler had calculated the 2p-1s transition energy in Pb, using the then accepted nuclear radius 1.4 A1/3 fermi, to be around 4.5 MeV. Correspondingly, they had set the spectrometer to look in that energy region. After several frustrating days, Rainwater suggested broadening the range and then the peak appeared - not at 4.5 MeV but at 6 MeV! The nucleus was substantially smaller than had been deduced from other effects. Shortly afterwards Hofstadter got the same results from his electron scattering experiments. While the µ-mesic atom measurements give the rms radius of the nucleus with extreme accuracy the electron scattering results have the advantage of yielding many moments to the charge distribution. Now the best information is obtained by combining the results from both µ-mesic atoms and electron scattering. Subsequently, in making precise gamma-ray measurements to obtain a better mass value for the µ-meson, it was found that substantial corrections for the vacuum polarization were required to get agreement with independent mass determinations. While the vacuum polarization is about 2% of the Lamb shift in hydrogen it is the very dominant electrodynamic correction in µ-mesic atoms. Dr. Fitch's interest then shifted to the strange particles and K mesons, but he had learned from his work at Columbia the delights of unexpected results and the challenge they present in understanding nature. Dr. Fitch took a position at Princeton where, most often working with a few graduate students, he spent the next 20 years studying K-mesons. The ultimate in unexpected results was that which was recognized by the Nobel Foundation in 1980, the discovery of CP-violation. At any one time there is a natural tendency among physicists to believe that we already know the essential ingredients of a comprehensive theory. But each time a new frontier of observation is broached we inevitably discover new phenomena which force us to modify substantially our previous conceptions. Dr. Fitch believed this process to be unending, that the delights and challenges of unexpected discovery will continue always. In 1967 he and Jim Cronin received the Research Corporation award for work on CP violation and in 1976 the John Price Witherill medal of the Franklin Institute. He received the E. O. Lawrence award in 1968. Dr. Fitch was a fellow of the American Physical Society and the American Association for the Advancement of Science, a member of the American Academy of Arts & Sciences and the National Academy of Sciences. He was elected a member of the American Philosophical Society in 1995. He served as chairman of the Physics Department at Princeton University and was James S. McDonnell Distinguished University Professor of Physics Emeritus at the time of his death February 5, 2015, at age 91.
 
Election Year
1995[X]