Donald Stewart Gemmell

Rare is the research scientist who can claim to have influenced as many fields of science as Don Gemmell did throughout his career as an experimental physicist at Argonne National Laboratory from 1963 until his recent death on the 29th of August 2013. His work spanned nearly all of physics, producing important results in nuclear, atomic, molecular, solid-state, x-ray, astro- and biophysics as well as chemistry. Among a broad international community, he was perhaps best known for his extensive early researches in ion-solid interactions and his exploration of how fast ions can be shepherded by the coherent effect of crystals in ‘channeling’ and blocking’. His 1974 Reviews of Modern Physics article on the subject[1] has long been known as the “Bible” for workers in the field.

Donald S. Gemmell was born in Adelaide, South Australia in 1934. Following undergraduate education at the University of Adelaide, he continued his studies at the Australian National University, Canberra, where he completed his Ph.D. thesis in 1959 working with Sir Ernest Titterton exploring Giant Resonances in light nuclei. After 3 years as a Commonwealth Research Fellow at the Atomic Energy Research Establishment, Harwell, England, he joined the staff of the Physics Division at Argonne National Laboratory in 1963, serving as Director of that Division throughout the 80’s and early 90’s and then returning to active research for the final decade of his career.

He was a pioneer in the field of accelerator-based atomic physics in the 60’s and 70’s when he developed the techniques to study motions of fast ions first in channelling and blocking in crystals and then extending that to the channeling of molecular ions. Later, collaborating with his old friend Zeev Vager of the Weizmann Institute, they began to explore the same effects observed with molecules in thin amorphous films, leading to the study of electron polarization wakes[2] (now being exploited as an acceleration technique[3] ) and subsequently the Coulomb Explosions of molecules. One constant trademark of his research was to work at the interface between scientific fields and to break new ground by applying techniques from one field as a new method in another field. Having been trained in nuclear physics, he applied the techniques learned there to atomic physics and then, from his study of molecular ions in solids, turned to stereochemistry using coincident particle detection to begin Coulomb Explosion Imaging[4] as well as biology[5] .

After stepping down as Director of the Physics Division in 1992, he returned to research full time concentrating on synchrotron radiation physics, but once again crossing fields by studying Nuclear Excitation by Electronic Transition, a method of using x-ray radiation to excite the nucleus by transferring the electronic excitation energy to the nucleons[6] . In his final major research effort in 2005, and building on this experience with synchrotron radiation and nuclear physics, he played a key role in a nuclear physics collaboration to use such radiation to disprove a suggested x-ray induced decay in the 31-year isomer of ¹⁷⁸Hf[7] .

Beyond all of these research achievements, perhaps one of his most important contributions to experimental science was his very early recognition of the importance of digital computers in controlling experimental apparatus and in acquiring, recording, and analyzing data. While this is now so ubiquitous in physics experiments that it is hard to imagine physics without computers, Don was among the very first to start adapting computers to assist experiments in the 60’s and by the late 70’s he had developed a very sophisticated beam line in which all of the equipment was remote-controlled and monitored. When appointed to an ANL committee to promote the use of microprocessors at the Lab, Don developed several systems to control accelerator consoles and, most importantly, an early color graphics display composed of a simple microcomputer driving a 24" Zenith color TV set (the biggest screen he could purchase for less than $500 as required by Lab policies at the time). Also, long before the first laptop computer, he attached a carry handle to one of his microcomputers to bring it home each night to continue his programming. Perhaps his favorite publication was an internal document he titled “Whaddayadoo with the Didjeridoo” which served as an operating manual for users of his program on an ASI-2100 computer for processing data from a pulse-height analyzer, one of the very first such computer-based data acquisition systems ever used in a nuclear physics experiment. Outside of the laboratory, in addition to his family and many friends around the world, his greatest passion was flying, both model airplanes and real ones.

1. 1. D. S. Gemmell, Rev. Mod. Phys. 46, 129 (1974).
2. 2. Z. Vager and D. S. Gemmell, Phys. Rev. Lett. 37, 1352 (1976).
3. 3. C. Joshi and T. Katsouleas, Phys. Today 56, 6 47 (2003) doi:10.1063/1.1595054 .
4. 4. D. S. Gemmell, Chemical Reviews 80, 301 (1980).
5. 5. E. L. Lloyd, M. A. Gemmell, C. B. Henning, D. S. Gemmell, and B. J. Zabransky, Int. J. Ratiat. Biology 35, 23 (1979).
6. 6. I. Ahmad, R. W. Dunford, H. Esbensen, D. S. Gemmell, E. P. Kanter, U. Rütt, and S. H. Southworth, Phys. Rev. C 61, 051304 (2000).
7. 7. I. Ahmad, J. C. Banar, J. A. Becker, T. A. Bredeweg, J. R. Cooper, D. S. Gemmell, A. Kraemer, A. Mashayekhi, D. P. McNabb, G. G. Miller, et al., Phys. Rev. C 71, 024311 (2005).