Diffusion of atoms and molecules on interstellar dust grain and ice analogs

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Interstellar space, or the space between the stars, contains extremely cold and tenuous clouds of gas seeded with tiny dust grains. Within the densest interstellar clouds, dust grains are coated with ice, providing sites for chemical reactions of simple atoms and molecules. Reactions on dust grains and ices can produce increasingly complex molecules, some of which are the building blocks of life. This research project will use advanced experimental and theoretical tools from a variety of scientific fields to study how atoms and molecules react on dust grains and ices under harsh conditions similar to those in space. Results from the study will help astronomers understand how processes on dust grains and ices can lead to the rich chemistry of space. The project will also train students in an interdisciplinary field at the forefront of astrophysical research. This project will combine proven experimental techniques (atomic and molecular beams, quadrupole mass spectrometry, and infrared spectroscopy) with new techniques (time-resolved reactive scattering) to obtain quantitative information on adsorption, diffusion, reaction, and desorption of atoms and molecules that are commonly found in the interstellar gas. Newly developed theoretical methods will be used to derive adsorption (sticking) and diffusion coefficients of the atoms and molecules from the experimental data. The data and derived parameters will be used in simulations of interstellar environments. The PI and his team will: (1) measure diffusion coefficients of atoms and molecules on surfaces of dust grain analogs and ices; (2) measure sticking coefficients of atoms and molecules on surfaces of various grain analogs; (3) perform theoretical analyses of the experimental data; (4) use the new diffusion coefficients in chemical models that will help interpret observations of interstellar clouds; and (5) provide the data in a format that can be used by astronomers studying the chemical evolution of the interstellar gas. The project will also support an undergraduate student, a graduate student, and a postdoctoral scholar at Syracuse University.