Eldon Earl Ferguson

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ELDON EARL FERGUSON

This collection of papers represents a special issue of the International Journal of Mass Spectrometry and Ion Processes in honour of Eldon Ferguson. It comprises contributions by many of his closest friends and admirers and recognises his enormous contribution to ion physics and chemistry on the occasion of his retirement from the Directorship of the Aeronomy Laboratory, NOAA, Boulder, Colorado, U.S.A. Eldon Earl Ferguson was born at Rawlins, Wyoming, U.S.A. on 23rd April, 1926, but was raised in Tulsa, Oklahoma from the age of 5 years. His earliest academic aspiration was to become a history teacher but, fortunately for us, his better grades in science directed him towards a career in science, so he entered the University of Oklahoma at Norman to train as a physicist. Following his BS (1949) and MS (1950) degrees, he entered graduate school to research into IR and Raman spectroscopy, which gave him a grounding in both experimental and theoretical physics. He was awarded his Ph.D. in 1953. His professional life began with the Phillips Petroleum Company in Oklahoma as a geophysicist where he spent one year involved in seismology. In 1955, he moved to the Naval Research Laboratory in Washington, DC where he researched into the IR spectroscopy of charge transfer complexes. His work in this area was described by Mulliken as “brilliant”, an adjective which well describes much of his subsequent research into ion/neutral reactions for which he is best known. His profitable research period at the NRL ended in 1957 when his inherent desire both to teach and for greater freedom in research led him back to academic life and to a faculty position in the Physics Department at the University of Texas at Austin where he stayed for five years researching into IR spectroscopy and Penning ionization. During that period, he spent one year at the Max-Planck-Institut in Munich as a Guggenheim Fellow researching into plasma physics, but of much greater significance during that period was that he was joined by Fred (F.C.) Fehsenfeld and Art (A.L.) Schmeltekopf as graduate students. Thus began a most productive scientific relationship which many of us in the ion physics and chemistry community have been thankful for. In 1962, Eldon moved to Boulder, Colorado to take up a position in the ESSA section (which later became NOAA) of the Department of Commerce. Recognising the talents of Art and Fred, he invited them to join him. The brief of the team was to research into ionospheric physics and, to that end, they began

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to build a stationary afterglow plasma system, a system which we also were utilizing at that time. While waiting for parts, equipment, etc., Art Schmeltekopf went to work in Broida’s Washington NBS laboratory for a month where he saw at first hand the flow tube spectroscopic light sources in that famous laboratory. Art persuaded Broida’s group to run a helium flowing afterglow and this they did, looking only at the radiation emission. On returning to Boulder, he reported this to Eldon and Fred and in discussion they realised that, if a mass spectrometer detection system was included at the downstream end of the flow tube, then ion chemistry could be studied in the flowing plasma. Thus, the flowing afterglow as we know it was born. The rest is history. The outstanding physical insight and laboratory skills of the team, coupled with the exceptional leadership qualities of Eldon, ensured that the flowing afterglow technique became one of the most versatile and productive apparatuses ever devised for chemical physics research. The versatility of the technique and the skill and extraordinary efforts of Eldon’s group are what legends are made of. At the inception of the flowing afterglow, the rate coefficients (or should we say rate constants!?) of perhaps 100 reactions were known (approximately) due to the valiant efforts of many pioneers in the field using various other techniques. After just a few years in the hands of Eldon’s group at Boulder, the flowing afterglow had yielded the rate coefficients for hundreds of ion/neutral reactions and in doing so laid the foundation for a clear understanding of ion/neutral reaction mechanisms and of the ion chemistry of the terrestrial ionosphere. The gloriously productive 20 year period of ion chemistry in Eldon’s laboratory saw numerous advances. Of note are the discovery of the origins of water clusters in the D-region of the ionosphere, the classic work on the effect of vibrational excitation in N, on its reaction with O+ ions, the pioneering work on associative detachment and on ion-atom reactions, and the beautiful work on the collisional quenching of vibrationally excited ions, which continues to be an exciting area of ion chemistry. It would do Eldon a great disservice if it were not stated that he constantly praises the major contribution made to this work by Art and Fred and Dan (D.L.) Albritton, as well as a succession of talented visiting scientists who were attracted to his laboratory. So many young scientists (from many countries including N.G.A.) have so much to thank Eldon for. He would not suffer fools gladly but, though forever busy and involved in his work, he was prepared to go to great lengths to encourage and advise enthusiastic and motivated young scientists. Needless to say, his scientific reputation grew rapidly as his publication list grew (currently numbering over 200 papers in prestigious journals). Many honours have resulted, including the Department of Commerce Gold Medal (in 1966 and 1982), the American Chemical Society Award, Colorado

ix Section, 1977 and the Presidential Rank Award, Meritorious Executive, Department of Commerce, 1980. He has been an Associate Editor of the Journal of Chemical Physics and of the Journal of Geophysical Research, to mention just two. He has been a member of the Fachbeirat-Kosmochemie of the MPI fur Kernphysik (Heidelberg) for more than ten years, as well as a member of other prestigious national and international committees. On his retirement from NOAA on the occasion of his sixtieth birthday, he left the United States to live in France following an appointment as Directeur de Recherche du CNRS based in Orsay. A motivation for this radical move was his marriage to Marie Durup, and perhaps an appreciation of the delights of European culture? What is certain is that his scientific life, and in particular his involvement in ion chemistry, has, if possible, intensified. He has become a focus and a stimulus for research in ion chemistry in Europe, a role he thoroughly relishes, and European science is the better for his involvement. Is it possible that we have not yet seen the best of Eldon? Certainly, we in the wider scientific community wish him well and thank him for his massive contribution to ion chemistry and for the scientific stimulus he has provided to so many of us. The immediate positive response to our invitations to contribute papers to this special volume, from established and up-and-coming scientists alike, attests to their respect and admiration for Eldon. Indeed, the response was such that it was necessary to divide the volume into a Part A and a Part B. We whole-heartedly join in the applause for Eldon and, together with the ion chemistry community, look forward to his continuing contributions to this exciting area of research. Nigel G. Adams David Smith