RUI: Structure and Dynamics of Negative Ions

Denison University, Granville OH

Investigators

Abstract

Negative ions are important in a variety of physical processes including Earth's atmosphere, stellar atmospheres and electrical discharges and plasmas. The broader impacts of this research program include contributions to the database of atomic properties, connections to other scientific fields, and the education and training of undergraduate students. Lasers will be used to measure the properties of negative ions, which are atoms and molecules that have an extra electron. Since ions are electrically charged particles, they can be manipulated to allow precise experiments. The high-precision measurements of electron binding energies in this project will be useful for modeling of chemical reactions and plasma interactions for such practical applications as semiconductor processing, lighting and plasma displays. The detailed studies of negative ions will yield insights into dynamical many-body interactions, which is a general topic of interest for a broad range of fields in physics, chemistry, materials science, and nanotechnology. The project will enhance the research and teaching infrastructure of Denison University, an undergraduate college. Students will participate in the experiments on-campus, providing important research experiences for young scientists including technical training in electronics, computers, vacuum systems, lasers, and optics. This project studies the interactions of photons with negative ions in a series of pulsed-laser photodetachment experiments. The extra electron in a negative ion is bound predominantly by electron correlation effects and therefore negative ions provide a fertile testing ground for state-of-the-art atomic physics calculations regarding these multi-body interactions. Complex atomic negative ions are investigated on-campus at Denison University using tunable infrared laser light to detach outer-shell electrons from negative ions produced in a sputter source. The ground and upper state photodetachment thresholds of several lanthanide and Group III negative ions (Lanthanum and Thallium) will be measured in order to determine the electron affinities and energy levels. These experiments will help explain the current strong disagreement between theoretical predictions and experimental photoelectron spectroscopy results for these interesting systems. The faculty and student researchers will investigate resonances and bound excited states in lanthanide ions including bound-bound electric-dipole transitions that exist in the negative ion of La. Additional studies will investigate inner-shell photodetachment from carbon chain negative ions and two-electron photodetachment processes. The dynamic multi-electron interactions in the photoexcitation and decay of the highly correlated cores of negative ions continue to challenge the fundamental understanding of atomic structure. The series of experiments in this project will test the latest theories describing photodetachment and negative ion structure.