Dr. Stuart ElstonProfessor
Ph.D., University of Massachusetts, 1975
Office: 515 Nielsen Physics Building
Electron emission from atomic collisions; grazing-incidence ion-surface collisions
Collisions between atomic particles - atoms, ions, and electrons - are responsible for diverse phenomena occurring in environments ranging from interstellar clouds and stellar atmospheres on an astronomical scale, to laser plasmas and effects of radiation on biological systems on the human scale, to molecular rearrangement (chemistry) and surface modification and corrosion on a microscopic scale. In many - perhaps most - cases, the excitation energy delivered in an atomic or ionic collision results in the emission of electrons. The distribution of emitted electrons, in energy and in direction, carries a wealth of information about the processes responsible for their ejection and about the structure of the colliding particles. The study of electron emission can therefore provide insight into fundamental mechanisms and serve as the basis of analytic techniques.
My research studies collisions of accelerator-produced projectile ions with atoms, molecules, bulk solids, and surfaces, emphasizing the observation and interpretation of electron emission produced during such collisions. Early work demonstrated that the energy and angular distribution of electron emission in the extreme forward direction, at speeds nearly matching that of the projectile ion - and corresponding to the emission of so-called 'convoy' electrons - provides a particularly sensitive probe of collision inter-actions capable of resolving different emission mechanisms such as target electron capture and projectile electron loss. This work is conducted primarily at the Oak Ridge National Laboratory EN Tandem Van de Graaff Accelerator Facility and uses imaging charged particle detection to add simultaneous directional resolution to otherwise conventional electrostatic deflection electron spectrometry.
Methods developed to study binary ion-atom collisions have been extended to more complex ion-solid collision systems to demonstrate in detail that plural- and multiple-collision phenomena responsible for electron emission in bulk solids can be accurately modeled by successive ion-atom collisions that prepare an excited projectile state which then undergoes a final ionizing event. Similar methods are presently being applied to collisions at shallow angles of incidence with atomically clean, single crystal surfaces, and focus on the use of electron emission to probe the dynamically evolving surface image potential that develops in response to the passing projectile ion.
Brief VitaProfessor Stuart B. Elston received the B.S. degree in Physics from Rochester Institute of Technology in 1968 and, following two years of service in the United States Marine Corps, earned a Ph.D. in Physics from the University of Massachusetts at Amherst in 1975. After two years as a Postdoctoral Research Associate and two years as Research Assistant Professor, he joined the faculty at the University of Tennessee in 1979. He has also held a part-time position as Adjunct R and D Participant in the Physics Division at Oak Ridge National Laboratory from 1979 to 1996.