Theoretical Investigation of PAHs : Implications to Diffuse Interstellar Bands
Theoretical Investigation of PAHs : Implications to Diffuse Interstellar Bands
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多环芳烃的理论研究：对弥漫星际带的影响
DOI：
10.1017/s1743921313016104
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
P. J.
中科院分区：
文献类型：
--
作者：
Pathak;A. ; Buragohain;M. ; Hammonsds;M. ; Sare;P. J.
在星际消光曲线上，大约有一千个光学吸收特征被观测到，这些特征通常被称为星际漫射带（DIBs）。由于望远镜和光谱技术的改进，这些数字每年都在增加。与一些DIB相对应的超高分辨率光谱观察和发射特征表明，其中一些（如果不是全部）特征是由大分子引起的。DIB的强度取决于红化的量，红化的量与背景星星和观测者之间存在的物质的量成正比。由于DIB的强度彼此之间没有很强的相关性，因此必须有几个载波。时间依赖密度泛函理论（TDDFT）的计算有助于缩小实验室研究的分子体系范围，未识别的红外（UIR）谱带的观测结果表明多环芳烃（PAH）分子广泛存在。虽然在星际空间中还没有发现一种PAH，但它们是被怀疑存在的最大分子。多环芳烃在星际条件下对高能环境是稳定的，使这些分子成为DIB载体的良好候选者。我们报告TDDFT计算预测电子跃迁的中性，质子化，氘化和多环芳烃与五员环的质子化和氘化的各种网站。与它们的中性形式相比，这些带电的等电子形式的多环芳烃被预测在可见光区具有活跃的跃迁，这意味着它们是合适的候选者作为载体的一些DIB和实验室研究是必要的这些系统。
About a thousand optical absorption features on the interstellar extinction curve popularly known as the Diffuse Interstellar Bands (DIBs) have been observed. The numbers are increasing every year, thanks to the improvement in telescope and spectroscopic technology. Ultra-high resolution spectroscopic observations and emission features corresponding to some of the DIBs suggest that, some if not all, of these features are due to large molecules. The strength of DIBs depend on the amount of reddening which is directly proportional to the amount of material present between the background star and the observer. Since, the strengths of the DIBs are not strongly correlated with each other, there must be several carriers. Time Dependent Density Functional Theory (TDDFT) calculations are useful in narrowing down molecular systems that may be further investigated in the laboratory.The observations of the unidentified infrared (UIR) bands point towards the widespread presence of Polycyclic Aromatic Hydrocarbon (PAH) molecules. Though, not a single PAH has been discovered in interstellar space, these are the largest molecules suspected to be present. PAHs are stable towards energetic environment prevailing under interstellar conditions rendering these molecules to be good candidates as DIB carriers. We report TDDFT calculations to predict electronic transitions of neutral, protonated-deuteronated and PAHs with five member rings with various sites of protonation and deuteronation. Compared to their neutral forms, these charged isoelectronic forms of PAHs are predicted to have active transitions in the visible region, which means they are suitable candidates as carriers for some of the DIBs and laboratory studies are warranted for these systems.