Untangling the Energetics and Dynamics of Reactions of Ground State Silylidyne Radicals with Mononuclear Main Group Hydrides

University Of Hawaii, Honolulu

Investigators

Abstract

In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Ralf I. Kaiser of the University of Hawaii at Manoa is exploring chemical reactions between a simple molecule containing one silicon and one hydrogen atom (SiH, formal name "silylidyne") with other molecules such as water (H2O), hydrogen sulfide (H2S) and ammonia (NH3). Similar reactions between simple carbon molecules and H2O, H2S and NH3 are well-studied, but little is known about the corresponding silicon reactions. The chemistry of carbon and silicon are similar in many ways, even to the point that some scientists have asked the question, "why is life on Earth based on the element carbon, and not silicon?" Professor Kaiser's research is exploring the differences in chemical reactivity of molecules containing silicon and carbon, and is providing insights into chemical reactions in general. This research is also broad implications and directly contributes to an ongoing effort by astrochemists and astrobiologists to connect the chemistry of space to the birth of stars, the formation of planets, and the evolution of life. More broadly, this project impacts society through the dissemination of its research results, through outreach activities to researchers, college students, and high school teachers via interdisciplinary symposia, by broadening the participation of underrepresented minorities, and by relaying the project's latest breakthroughs directly to educators enabling them to incorporate research activities into classroom curricula. By conducting state-of-the-art crossed molecular beam experiments of ground state silylidyne radicals (SiH) with prototype mononuclear main group (IV - VI) hydrides and combining these results with ab initio and quasi-classical trajectory (QCT) calculations in collaboration with Prof. Martin Head-Gordon (UC Berkeley), the proposed investigations explore the hitherto elusive chemical dynamics of silicon-bearing systems and untangle the formation of exotic dinuclear silicon-carrying molecules, of which many have only been predicted to exist theoretically. The project is advancing the fundamental understanding of the chemical bonding of silicon-based molecules, transform the knowledge of the unimolecular decomposition of chemically activated silicon-bearing reactive intermediates and evaluate the processes which control them, establish predictive concepts of non-adiabatic reaction dynamics in silicon-bearing molecular systems, and illuminate the perception of isovalency on the molecular level by comparing the reaction dynamics of the silylidyne radical (SiH) with those of the isovalent methylidyne (CH) systems. Participating graduate and undergraduate students are being trained in cutting-edge laboratory techniques (reactive scattering experiments, ultra-high vacuum setups, laser techniques) along with data analysis and dissemination of their research results in peer-reviewed journals. The PI's group also plans an annual one-week National Summer Teacher Workshop, aimed at teachers from local and mainland high schools, that emphasizes hands-on laboratory activities in astrochemistry and how the results from fundamental research in gas phase chemistry (reaction mechanisms, chemical dynamics) are applied to better understand the chemistry occurring in the solar system (comets, meteorites, planets and moons) and interstellar medium. 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.