RUI: Ultrafast Dynamics in Discrete and Continuum Spectra of Some Symmetric Molecules and Derivatives

Northwest Missouri State University, Maryville MO

Investigators

Abstract

This award will study the details of microscopic structural changes resulting from ultrafast processes driven by laser and/or matter-particle collisions with symmetric-shaped molecules. The molecules and processes are chosen on the basis of their fundamental properties and behavior to advance the frontier of basic scientific knowledge in Physics and Chemistry. The studies are relevant to a wide array of applications, including in quantum computation, quantum information processing, molecular device & sensor design, organic solar-cell technology, hydrogen-molecule based energy production, photothermal cancer therapy, magnetic resonance imaging (MRI), and molecular-level slow electronics. While the primary research to be undertaken is based on computational simulations, collaborations with experimental groups will be developed, wherever possible, for the confirmation and extended understanding of the results. Meanwhile, undergraduate students, majoring in Physics, Chemistry, or even Computer Sciences, will be involved to enhance their educational experience and to motivate them for careers in research, industry, or academia. The scientific outcomes and the high level of student enthusiasm will be enhanced by the engagement of a Postdoctoral Fellow, providing advanced research/mentoring experiences. Finally, the development of machine learning algorithms for a future program will benefit from the knowledge learned and experience acquired. Preliminary computational methodologies, developed with our previous NSF awards enabling high-performance computing, will be further upgraded and applied for simulations needed for the research. Two primary processes to be considered are: (i) The evolution of excited electrons’ energy-distribution in time while their motion is coupled with the lattice vibration of their molecular host, and (ii) The ultrafast time-delay or time-advancement during particle scattering from a molecule or the laser-driven knockout (photoionization) of an electron from a molecule. In addition, to prepare selected results for direct experimental verification by other groups, the effect of a probe laser-pulse, routinely used in measurements, will also be simulated. The goal is to deploy these techniques to investigate the femto- and picosecond dynamics of charge transfer, excitonic decay, plasmon-exciton coupling, Jahn-Teller (J-T) distortion – all processes below the knockout energies (discrete spectra). While for higher energies (continuum spectra) the symmetry-induced diffraction in time-delay, dephasing of plasmon excitations, inter-coulombic decays, particle capture processes involving positron (electron’s antiparticle partner) impact positronium formations, all in attoseconds, will be accessed. Chosen polyhedral hydrocarbon molecules, fullerene molecules and derivatives including their polymerized functional versions and dimers will be considered. In a case-study of J-T distortion favored dissociation dynamics, excited states of methane cations will be addressed which will later be extended to ethylene and vinylidene cations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.