Metal-Containing Molecules as Probes of Interstellar/Circumstellar Gas: From Chemistry to Nucleosynthesis

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AST-0204913PI ZiurysDuring the past thirty years since the initial discovery of interstellar molecules at radio wavelengths, much has been learned about the chemistry of such species, and their subsequent use as tracers of the physical conditions in dense gas has proved extremely valuable. Despite the obvious success of molecular astrophysics, there are still many unanswered questions pertaining to interstellar molecules, one of which concerns the chemistry and abundances of species containing the metallic elements. This project will continue the investigation of the chemistry of the metallic elements in the interstellar medium through a joint laboratory/observational/chemical modeling program. The observations will identify the major molecular carriers of the metallic elements incircumstellar envelopes of evolved stars and in dense clouds through measurements in the millimeter/sub-mm wavelength region. This data will lead to the establishment of likely synthetic pathways, be it gas-phase radiative association reactions, dust-grain processes or formation in shock waves. The laboratory work will supply the necessary millimeter and sub-mm rotational spectra from which rest frequencies for the astronomical searches are obtained. Finally, chemical modeling of metal chemistry in circumstellar envelopes will be performed in conjunction with new nucleosynthesis calculations. A complete picture will thus be constructed of metal-containing molecules, their abundances, formation mechanisms, and significance for understanding mass loss of the heavier elements from circumstellar envelopes to the interstellar medium.***