论文标题
PAH光解离的影响对猎户座棒和马头PDR中小碳氢化合物的形成
Impact of PAH photodissociation on the formation of small hydrocarbons in the Orion Bar and the Horsehead PDRs
论文作者
论文摘要
我们研究多环芳烃（PAHS）是否可以成为光隔离区域（PDRS）中小碳氢化合物的重要来源。我们在两个良好研究的PDR，猎户座棒和代表PDR的原型典范的物理条件下，建模了20个特定PAH分子的演变，以脱氢和破坏碳骨架的脱氢和破坏。 PAH被描述为微型跨系统。乙炔分子被认为是PAH解离的主要碳质碎片，它是实验室实验和理论所遵循的。我们估计了气相化学反应中乙炔产生的速率，并通过PAH解离将其与乙炔产生的速率进行了比较。发现后者的费率可以高于Orion Bar中的以前的价格$ a _ {\ rm V} <1 $，也以$ a _ {\ rm V}> 3.5 $。在马头星云中，化学反应提供的乙炔比PAH解离更多。生产的乙炔参与了小碳氢化合物形成的反应（c $ _2 $ _2 $ h，c $ _3 $ h，c $ _3 $ _3 $ h $^{+} $，c $ _3 $ _3 $ _2 $ _2 $，c $ _4 $ h）。通过PAH破坏的乙炔产量可能会增加仅在$ a _ {\ rm V}> 3.5 $的猎户座棒中气相化学反应中产生的小碳氢化合物。在马云中，PAH对小碳氢化合物的丰富性的贡献可以忽略不计。我们得出的结论是，除了Orion bar中的某些位置，PAHS并不是两个PDR中小烃的主要来源。
We study whether polycyclic aromatic hydrocarbons (PAHs) can be a weighty source of small hydrocarbons in photo-dissociation regions (PDRs). We modeled the evolution of 20 specific PAH molecules in terms of dehydrogenation and destruction of the carbon skeleton under the physical conditions of two well-studied PDRs, the Orion Bar and the Horsehead nebula which represent prototypical examples of PDRs irradiated by "high" and "low" ultraviolet radiation field. PAHs are described as microcanonical systems. The acetylene molecule is considered as the main carbonaceous fragment of the PAH dissociation as it follows from laboratory experiments and theory. We estimated the rates of acetylene production in gas phase chemical reactions and compared them with the rates of the acetylene production through the PAH dissociation. It is found that the latter rates can be higher than the former rates in the Orion Bar at $A_{\rm V}<1$ and also at $A_{\rm V}>3.5$. In the Horsehead nebula, the chemical reactions provide more acetylene than the PAH dissociation. The produced acetylene participate in the reactions of the formation of small hydrocarbons (C$_2$H, C$_3$H, C$_3$H$^{+}$, C$_3$H$_2$, C$_4$H). Acetylene production via the PAH destruction may increase the abundances of small hydrocarbons produced in gas phase chemical reactions in the Orion Bar only at $A_{\rm V}>3.5$. In the Horsehead nebula, the contribution of PAHs to the abundances of the small hydrocarbons is negligible. We conclude that the PAHs are not a major source of small hydrocarbons in both PDRs except some locations in the Orion Bar.
