This article provides an overview of recent astronomical studies and a closely coordinated laboratory program devoted to the study of the physics and chemistry of carbon rich Asymptotic Giant Branch (AGB) stars. The increased sensitivity and angular resolution of high altitude ground-based millimeter-wave interferometers in the past few years has enabled molecular astronomers to determine the excitation and spatial distribution of molecules within a few stellar radii of the central star where the molecular seeds of dust are formed, and to critically assess the physicochemical mechanisms of dust formation and growth. However the astronomical studies are crucially dependent on precise laboratory measurements of the rotational spectra - both in the ground and vibrationally excited states of the normal and rare isotopic species - of the principal molecules in the inner region which appear to contain only two or three heavy atoms Much remains to be done by laboratory spectroscopists as evidenced by the large number of unassigned millimeters-wave rotational lines that are observed in the inner envelope of carbon rich AGB stars. As an illustration we refer to the example of an initial laboratory approach for establishing whether vibrationally excited SiC2 and HCN are the carriers of some of the unassigned features observed in the prototypical carbon rich AGB star IRC+10216 with ALMA. Also highlighted are ongoing laboratory studies of the silicon carbides SiC2 and SiCSi in their ground and excited vibrational states, and SiC3 in the ground vibrational state. Following the initial detection of SiC3 and SiCSi in the outer molecular envelope of IRC+10216, the laboratory spectroscopy was extended to higher frequency in support of the recent interferometric measurements. Thirty-two new millimeter-wave rotational transitions of SiCSi with J ≤ 48, Ka ≤ 3 and upper level energies Eu ≤ 484 K in the range from 178 - 391 GHz, and 35 new transitions of SiC3 with J ≤ 38, Ka ≤ 20 and Eu ≤ 875 K between 315 and 440 GHz were measured in the laboratory. In addition five to six rotational transitions in one quanta of each of the three fundamental vibrational modes of SiCSi, and the two lowest rotational transitions in the previously unexplored C-C stretching mode (ν 1) of SiCC were measured in the normal and doubly substituted 13C isotopic species.

中文翻译：

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尘埃的组成部分：AGB 恒星的协调实验室和天文研究。

本文概述了最近的天文学研究和一个密切协调的实验室计划，该计划致力于研究富碳渐近巨星分支 (AGB) 恒星的物理和化学。过去几年，高海拔地面毫米波干涉仪灵敏度和角分辨率的提高，使分子天文学家能够确定尘埃分子种子所在的中心恒星的几个恒星半径内分子的激发和空间分布。形成，并批判性地评估粉尘形成和生长的物理化学机制。然而，天文学研究主要依赖于对内部区域主要分子的旋转光谱的精确实验室测量——包括正常和稀有同位素物质的地面和振动激发态——内部区域的主要分子似乎只包含两个或三个重原子实验室光谱学家还有很多工作要做，在富含碳的 AGB 恒星的内壳中观察到大量未指定的毫米波旋转线就证明了这一点。作为说明，我们参考了用于确定振动激发的 SiC2 和 HCN 是否是在具有 ALMA 的原型富碳 AGB 星 IRC+10216 中观察到的一些未指定特征的载体的初始实验室方法的示例。还强调了正在进行的对处于基态和激发态的碳化硅 SiC2 和 SiCSi 以及处于基态振动态的 SiC3 的实验室研究。在 IRC+10216 的外部分子包膜中初步检测到 SiC3 和 SiCSi 之后，实验室光谱扩展到更高频率以支持最近的干涉测量。32 次新的 SiCSi 毫米波旋转跃迁，J ≤ 48，Ka ≤ 3 和上层能量 Eu ≤ 484 K，范围为 178 - 391 GHz，以及 35 次新的 SiC3 跃迁， J ≤ 38，Ka ≤ 20在实验室测量了 315 和 440 GHz 之间的 Eu ≤ 875 K。除了 SiCSi 的三种基本振动模式中的每一种的一个量子中的五到六次旋转跃迁，