For his career in chemistry and atomic physics, the unifying feature of which is the dynamics of change through collision. He has been a pioneer in the fields of crossed-beam and molecular beam chemistry and atomic physics, channeling of ions in solids, and in recent insightful experiments using the apparatus of particle physics to cast light on the chemistry of the early universe.
Sheldon Datz is among the most creative experimental scientists of our time having distinguished himself as a leader for more than forty years in atomic, molecular, and optical physics, as well in physical chemistry, the field in which he received his doctoral degree. He is also known for his observation and measurement of dielectronic recombination, a dominant energy loss process in fusion-oriented high temperature plasma, and pair production.
The unifying feature of his forty-five year scientific career lies in his use of crossed molecular beams to study the dynamics of chemical reactions in atom-molecule collisions. His broad contributions have provided understanding of the mechanisms of interactions involving ions, electrons and photons with kinetic energies ranging from a milli-electron volt to many mega-electron volts; and have engendered new methods for probing the structure of surfaces and internal structure of metal crystals. Many of his discoveries have been seminal in nature, and the breadth of these activities is truly extraordinary.
In chemical dynamics, Dr. Datz and his colleague Dr. E.H. Taylor in 1955 published the first paper on the use of crossed molecular beam techniques to study chemical reactions could be studied under conditions that would allow observing properties that revealed the quantum interactions in single collisions. That result had long been a dream of chemists, but was presumed to be completely impractical. The very simplicity of this experiment made it clear even to young assistant professors that one could undertake similar experiments with rather modest investments in instrumentation. In this first and two succeeding papers, Datz and Taylor described methods to obtain described the experimental techniques necessary to study atom-molecule reactions and methods to obtain the detailed nature of chemically reactive collisions could be obtained. The famous Datz and Taylor papers of the 1950s and 1960s laid the foundation for an entirely new field of crossed molecular beam chemistry.
Datz' continuing work in this field resulted in the following: the first use of time of flight to measure translational to vibrational energy in atom-molecule and ion-molecule collisions; the first molecular beam study of the role of electronic excitation in chemical reactions, and the first demonstration of electronic energy transfer.
Dr. Datz's interest in ion-surface scattering stemmed from experiments he conducted that demonstrated for the first time that single atom-atom collisions could be studied, even if the target atoms were located on the surface of a solid. In inelastic-atom-molecule collisions, he introduced time-of-flight and particle counting techniques (translational spectroscopy) to study the transfer of translational to vibrational energy and dissociative collisions.
Datz has been similarly innovative in experiments demonstrating ion channeling in solids, an effect predicted theoretically by M. Robinson. In order to decrease the contribution of multiple scattering background in the surface scattering experiments, Datz used single crystal targets oriented so that the projectile either hit surface atoms or penetrated so deeply that they did not return. His experiments in this field resulted in the following: the first demonstration of coherent excitation of ions by the periodic potential in a crystal lattice; the discovery of electron and positron channeling radiation; the first demonstration that channeled ions interact with electrons in the crystal as a dense electron target; and the first demonstration that one can make quantitative measurements applicable to collisions in dense plasmas but with more monoenergetic collision conditions.
His experiments have created a research and training environment in which young scientists have grown and flourished. Moreover, he has used his standing in the international community to promote the exchange of information among scientists of all nations. For the past several years, he has been organizing yet another major international conference which will take place during his 75th year.
Sheldon Datz was born in New York City in 1927. He earned his B.S. and M.A. degrees at Columbia University in Chemistry and Physical Chemistry (1950-51) and his Ph.D. degree from the University of Tennessee in 1960. He began his career in 1951 as a research chemist at Oak Ridge National Laboratory, where he is now Senior Corporate Fellow. He has published over 250 papers in peer-reviewed journals and has taught and lectured worldwide. In 1998 Dr. Datz received the Davisson-Germer Prize, one of the highest honors bestowed by the American Physical Society.
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