Herbig Ae星周围苊烯C12H8到纯碳C12的天体化学演化
Astrochemical Evolution Step From Acenaphthylene C12H8 To Pure Carbon C12 Around A Herbig Ae Young Star
摘要：
采用第一性原理量子化学计算方法，分析了Herbig Ae星周围多环芳烃的天体化学演化步骤。为了简单起见，模型分子被选择为具有一个五边形与两个六边形组合的烃的苊烯（C12H8）。在原行星盘中，分子被来自中心恒星的高能光子照射并电离成阳离子（C12H8）n+。计算表明，从n=0到6，分子保持多环烃构型。然而，在电离步骤n=7时，发生（C12H8）脱氢成纯碳（C12）。这种多环纯碳（PPC）将再次受到光子的攻击。在第八电离（C12）8+的阶段，发生分解为脂肪族碳链、C9、C2和单碳C1。计算这些步骤的红外光谱（IR）以鉴定观察到的光谱。通过（C12H8）2+和（C12H8）1+的组合鉴定了Herbig Ae星WW Vul和HD 145263的载体分子。HD 37357的红外光谱可用（C12H8）2+、（C12H8）3+和（C12H8）1+解释。纯碳分子在许多恒星中起着重要的作用。采用纯碳（C12）2+、烃（C12H8）2+和中性（C12H8）0+混合物对HD 37258进行了红外光谱分析。用（C12）2+、（C12H8）2+和（C12H8）3+分析了HD38120的络合物光谱。苊烯相关分子只是一个典型的例子。我们应该应用不同大小的分子来理解新生恒星周围的整体景象。
英文摘要：
Astrochemical evolution step of polycyclic aromatic hydrocarbon (PAH) around a Herbig Ae young star was analyzed using the first principles quantum chemical calculation. For simplicity, model molecule was selected to be acenaphthylene (C12H8) with hydrocarbon one pentagon combined with two hexagons. In a protoplanetary disk, molecules are illuminated by high energy photon from the central star and ionized to be cation (C12H8)n+ . Calculation shows that from n=0 to 6, molecule keeps its polycyclic hydrocarbon configuration. Whereas, at ionization step n=7, there occurs dehydrogenation of (C12H8) to pure carbon (C12). Such polycyclic pure carbon (PPC) would be attacked again by photons. At a stage of eighth ionization (C12)8+, there occur decomposition to aliphatic carbon chains, C9, C2, and mono carbon C1. Infrared spectra (IR) of those steps were calculated to identify observed spectra . Carrier molecules of Herbig Ae star WW Vul and HD145263 were identified by a combination of (C12H8)2+ and (C12H8)1+. Also, IR of HD37357 could be explained by (C12H8)2+, (C12H8)3+, and (C12H8)1+. Pure carbon molecules play an important role in many stars. IR of HD37258 was analyzed by a mixture of pure carbon (C12)2+, hydrocarbon (C12H8)2+ and neutral (C12H8)0+. Also, complex spectrum of HD38120 was analyzed by (C12)2+, (C12H8)2+ and (C12H8)3+. Acenaphthylene related molecules are just a typical example. We should apply various size molecules to understand total view around a new born star.
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