Polyacenes and diffuse interstellar bands
Polyacenes and diffuse interstellar bands
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DOI：
10.1051/0004-6361/201834953
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发表时间：
2019-05-07
影响因子：
6.5
通讯作者：
Toenshoff, C.
中科院分区：
文献类型：
--
作者：
Omont, A.;Bettinger, H. F.;Toenshoff, C.
除了五个属于C-60（+）的谱带外，弥漫星际带（DIB）的载体的识别仍有待确定，尽管人们普遍认为DIB载体应该是气相中的大碳基分子（类似于10-100个原子），如多环芳烃（PAH），长碳链或富勒烯。本文的目的是研究多环芳烃中更具体的可能载体，即细长分子，这可以解释DIB波长与其载体的表观紫外线弹性之间的相关性。更具体地说，我们解决的情况下，聚并苯，C4 N +2 H2 N +4，与N类似的10-18稠合直线排列的六边形。多并苯是有吸引力的DIB载体候选者，因为它们的高对称性和大的线性尺寸允许它们在可见光范围内形成规则的一系列带，其强度大于大多数其他多环芳烃，如最近的实验室结果所证实的十一并苯（C46 H26）。那些在DIB光谱域中具有非常强的谱带的化合物刚好处于抗UV光解离的稳定极限。它们是星际碳化合物中重要的PAH家族的一部分，这意味着只有大约10（-5）的PAH丰度才足以解释中等强度的DIB。在总结了有限的当前知识的复杂性能的聚并苯和最近的实验室结果，他们可能会满足的标准，一些DIB载体的可能性是通过审查以下属性：波长和强度的一系列可见波段;星际稳定性和丰度，电荷状态和氢化;和DIB旋转配置文件。没有明确的不一致性被确定为排除多并苯作为具有中等或弱强度的一些DIB（包括所谓的C（2）DIB）的载体。但是，尽管它们有许多有趣的特性，但还需要更多关于长并苯及其可见光谱带的实验数据才能得出可靠的结论。
The identification of the carriers of the diffuse interstellar bands (DIBs) remains to be established, with the exception of five bands attributed to C-60(+), although it is generally agreed that DIB carriers should be large carbon-based molecules (with similar to 10-100 atoms) in the gas phase, such as polycyclic aromatic hydrocarbons (PAHs), long carbon chains or fullerenes. The aim of this paper is to investigate more specific possible carriers among PAHs, namely elongated molecules, which could explain a correlation between the DIB wavelength and the apparent UV resilience of their carriers. More specifically, we address the case of polyacenes, C4N+2H2N+4, with N similar to 10-18 fused rectilinear aligned hexagons. Polyacenes are attractive DIB carrier candidates because their high symmetry and large linear size allow them to form regular series of bands in the visible range with strengths larger than most other PAHs, as confirmed by recent laboratory results up to undecacene (C46H26). Those with very strong bands in the DIB spectral domain are just at the limit of stability against UV photodissociation. They are part of the prominent PAH family of interstellar carbon compounds, meaning that only similar to 10(-5) of the total PAH abundance is enough to account for a medium-strength DIB. After summarizing the limited current knowledge about the complex properties of polyacenes and recent laboratory results, the likelihood that they might meet the criteria for being carriers of some DIBs is addressed by reviewing the following properties: wavelength and strength of their series of visible bands; interstellar stability and abundances, charge state and hydrogenation; and DIB rotation profiles. No definite inconsistency has been identified that precludes polyacenes from being the carriers of some DIBs with medium or weak strength, including the so-called C(2)DIBs. But, despite their many interesting properties, additional experimental data about long acenes and their visible bands are needed to make robust conclusions.