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

自首次发现射电波段的星际分子以来，在过去的30年里，人们已经了解了许多关于这种物种的化学物质，后来它们被证明是非常有价值的，作为稠密气体中物理条件的示踪剂。尽管分子天体物理学取得了明显的成功，但关于星际分子仍有许多悬而未决的问题，其中之一涉及含有金属元素的物种的化学和丰度。该项目将通过联合实验室/观测/化学模拟方案继续研究星际介质中金属元素的化学。观测将通过在毫米/亚毫米波长区域的测量，确定演化恒星的星际包层和致密云中金属元素的主要分子载体。这些数据将导致可能的合成路径的建立，无论是气相辐射缔合反应、尘埃-颗粒过程还是在冲击波中形成。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静止频率。最后，将结合新的核合成计算，对星周包层中的金属化学进行化学模拟。因此，一幅完整的图景将由含有金属的分子、它们的丰度、形成机制以及对理解较重元素从星际包层到星际介质的质量损失的意义来构建。

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.***