All ETDs from UAB

Advisory Committee Chair

Perry A Gerakines

Advisory Committee Members

Renato P Camata

David J Hilton

Reggie L Hudson

Charles L Watkins

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The abundances of ices in planetary environments are obtained through measurements of near-infrared absorption features (&nu=10,000-4,000 cm-1, &lambda=1-2.5 &mum), and near-IR measurements of materials present in the interstellar medium are increasingly common. In the studies presented here, the near-IR band strengths for molecules are determined through correlations to their better-known mid-IR characteristics. These strengths are used to determine the column densities of molecules in the interstellar dense cloud or other environments from observed data. The first set of experiments is focused on the near-IR features of molecules relevant to the study of interstellar icy grain mantles and planetary bodies: CO, CO2, C3O3, CH4, H2O, CH3OH, and NH3. The spectra of these species were studied in the near-IR region from 10,000-3,500 cm-1 and in the mid-IR region from 4500-400 cm-1 during the slow growth of films at 5 K. The results were then used to determine the near-IR band strengths of each molecule. Many icy satellites have surfaces that are dominated by either N2 or H2O and ices in the ISM are primarily composed of H2O. The second set of experiments is focused on the near-IR absorption features of CO, CO2, CH4, and NH3 diluted in H2O and diluted in N2. Since the compositions of icy planetary bodies and interstellar ices are affected by processing due to UV light or proton bombardment, spectra of UV photolyzed and proton irradiated mixtures of N2 + CO2 and H2O + CO2 have been collected to determine the extent of energetic processing on icy bodies in the outer solar system. These studies have shown that planetary ices are best represented by laboratory analogs comprised of mixed, energetically processed ices.

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