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

在过去的30年里，自从在无线电波长上发现星际分子以来，人们对这类物质的化学性质已经了解了很多，而且后来将它们作为致密气体中物理状况的示踪剂被证明是极有价值的。尽管分子天体物理学取得了明显的成功，但仍有许多关于星际分子的未解之谜，其中之一涉及含有金属元素的物种的化学成分和丰度。该项目将通过联合实验室/观测/化学建模计划，继续研究星际介质中金属元素的化学性质。观测将通过毫米/亚毫米波长区域的测量，确定演化恒星的星周包层和稠密云层中金属元素的主要分子载体。这些数据将导致建立可能的合成途径，无论是气相辐射结合反应，尘粒过程还是冲击波形成。实验室工作将提供必要的毫米和亚毫米旋转光谱，从中获得天文搜索的休息频率。最后，将与新的核合成计算一起进行星周包膜中金属化学的化学建模。因此，一个完整的图像将构建含金属分子，它们的丰度，形成机制，以及对理解从星周包层到星际介质的重元素质量损失的意义

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.***