Ice in the interstellar medium exists in a range of compositions and structures depending on its environment and physicochemical history. From its formation in molecular clouds to its incorporation into protoplanetary disks and eventually into planetary systems, interstellar ice is subject to energetic processes including interaction with photons and cosmic rays, heating and cooling, and chemical reactions in and on the ice, all of which will modify its structure (amorphous or crystalline), composition, and state (solid to gas, and back again). Interstellar ices are observed principally via their IR absorption bands along lines of sight towards continuum point sources. Information about the observed ices, including the determination of their structure and composition, can be inferred by comparison to laboratory experimental and theoretical studies, most directly via IR spectroscopic studies. There are inherent difficulties in the study of bulk, amorphous solids using IR spectroscopy, most notably the widening of IR absorption bands in the solid phase, causing blending of features. This in conjunction with observational limitations such as telluric absorption, instrument sensitivity and spectral resolution, has thus far prevented the identification of the exact composition and structure of interstellar ices. However, despite such constraints, IR spectroscopy remains a powerful technique for generating molecular level information on ices in the laboratory. In this talk I will present some recent laboratory studies of ices, using examples of ice mixtures and selective irradiations to show how, despite its broad absorption features, we can extract precise information about an ice's structure using only IR spectroscopy. Studies of this type will be critical in interpreting data from future observations, including those from JWST, whose higher sensitivity and spectral resolution will allow us an unprecedented insight into the nature of interstellar ices.

Structure and composition of interstellar ice: Linking observations to laboratory studies via IR spectroscopy

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.