Roy Middleton, emeritus professor of physics at the University of Pennsylvania, died at home in Media, Pennsylvania, on 23 June 2004 after a prolonged illness.

Middleton was born on 3 October 1927 in Atherton, a suburb of Manchester, England. He took his first steps toward a scientific career at the nearby Wigan Technical College, a direction that in the English system of the time would have taken him into industry. The University of London recognized his ability, which gained him enrollment there. He received his BSc in physics in 1948 and earned a PhD in physics from Liverpool University three years later under the supervision of Leslie L. Green, who later became director of the Nuclear Structure Facility at Daresbury, UK.

The 8-MeV deuteron cyclotron at Liverpool was used for some of the earliest studies of direct nuclear reactions, and Middleton, first as a graduate student and then as a research associate, enthusiastically measured (d,p) angular distributions using photographic plates. That work led to his studying (d,n) reactions for his PhD thesis using recoil protons in nuclear emulsions as the detection method. He remained at Liverpool as a research associate until 1955.

That same year, Middleton accepted a position as scientific officer at the Atomic Weapons Research Establishment at Aldermaston, soon after it had acquired one of the first tandem Van de Graaff accelerators, an instrument ideal for exciting direct reactions. He was a supremely creative experimentalist, both in the planning and execution of experiments and in the development and use of accelerator peripheral equipment. Of particular significance was his use of a multiple-gap charged-particle spectrometer for observing the products of nuclear reactions. The instrument allowed rapid accumulation of large amounts of data that unraveled the structures of scores of nuclei. The University of Pennsylvania took notice of that work and Middleton’s skills with the then new tandem accelerator, and invited him to direct the new Tandem Accelerator Laboratory. He joined the faculty there in 1965 as a professor of physics.

Tandem accelerators achieved a new versatility and ease of operation through Middleton’s development of a negative-ion source capable of producing useful currents from a large fraction of the periodic table. His related resource document, which he called the “Negative-Ion Cookbook,” circulated as the bible of the nuclear physics and, later, accelerator mass spectrometry communities. He was later (1979) awarded the American Physical Society’s Tom W. Bonner Prize for his work on the development and use of ion sources.

Middleton entered the field of accelerator mass spectrometry very early and collaborated with Jeffrey Klein of Penn and with Fouad Tera, Selwyn Sacks, and Julie Morris at the Carnegie Institution of Washington’s Department of Terrestrial Magnetism. Using beryllium-10, they demonstrated that lava from island-arc volcanoes had components that had once been on the ocean floor and had been subducted to the roots of volcanoes in transport processes lasting millions of years. Their results were reported in Geochimica et Cosmochimica Acta in 1986. Middleton developed or refined the accelerator method for the other cosmogenically generated isotopes carbon-14, aluminum-26, chlorine-36, and calcium-41. He actively participated in the science resulting from the use of those isotopes in a range of studies involving lunar samples, meteorites, tectites, and the erosion of rock surfaces and soils.

In collaboration with the Hospital of the University of Pennsylvania, Middleton produced the short-lived positron-emitting isotopes carbon-11, oxygen-15, and fluorine-18 for diagnostic studies of patients. The tracers were immediately transmitted to the hospital in gaseous form through tubing. That approach proved so successful that the hospital acquired a cyclotron to open the door to continued medical opportunities.

From 1986 to 1991, Middleton held the Andrew W. Mellon Foundation Professorship in physics at Penn. In his final years at university, he did outstanding work on negative ions, particularly on dianions, work often referred to in the literature of theoretical chemistry. He retired from Penn in 1996.

For thousands of undergraduate students, Middleton was an exceptionally effective, patient, and supportive teacher. If a student from his class in introductory physics needed his help, Middleton would, without complaint, interrupt his work at the tandem accelerator to provide that assistance. Although he taught the same course many times, he captured his students’ full attention with new notes and ideas. He brought to the classroom the same freshness and enthusiasm with which he approached his research. In 1969, the Lindback Foundation awarded him the Christian R. and Mary F. Lindback Award for Distinguished Teaching.

[Editor’s Note: Louis Brown, one of the authors of this obituary, did not live to see it published; he died on 25 September 2004. See his obituary on page 81 of this issue.]