The interaction of energetic atomic and molecular species with ice is of fundamental importance for both terrestrial and astrophysical chemistry. This presentation will examine our recent discovery of a new mechanism by which atomic and molecular species can enter ice, energetic ballistic embedding. This mechanism can lead to the direct absorption of species into the subsurface/selvedge region of ice formations, allowing for the laboratory investigation of fundamental kinetic and thermodynamic processes associated with the capture of such species. Our initial efforts, involving both experiment and numerical simulations, demonstrated the embedding of Xe and Kr. We have also explored the sticking of water on ice as well as the sputtering of ice in the hyperthermal regime using neutral atom bombardment. These studies revealed a rich palette of dynamics that are dependent upon the kinetic energy and momentum of the gas-surface encounter, the size and mass of the incident specie, as well as the nature of the ice itself including amorphous and crystalline ice. We have expanded these studies to include the energetic embedding dynamics of molecular systems, first CF4 and most recently CO2, with ice interfaces using a combination of in situ FTIR, scattering, and desorption measurements. The CO2/ice system is of particular interest because of its fundamental role in the Earth’s aqueous, atmospheric, permafrost, and seabed geosciences, as well as in the interstellar and circumstellar regions. These results show that energetic ballistic embedding in ice is a general phenomenon, and represents a significant new channel by which incident species can be trapped under conditions where they would otherwise not be bound stably as surface adsorbates. These studies have direct implications for environmental science including global warming, molecule storage and release from permafrost, glacial ice, clathrates, trace gas collection/release, and the composition of astrophysical icy bodies in space.

Energetic gas-surface encounters at ice interfaces

253rd National Meeting (2017)

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