CAN NEUTRAL AND IONIZED POLYCYCLIC AROMATIC HYDROCARBONS BE CARRIERS OF THE ULTRAVIOLET EXTINCTION BUMP AND THE DIFFUSE INTERSTELLAR BANDS?
CAN NEUTRAL AND IONIZED POLYCYCLIC AROMATIC HYDROCARBONS BE CARRIERS OF THE ULTRAVIOLET EXTINCTION BUMP AND THE DIFFUSE INTERSTELLAR BANDS?
复制标题
DOI：
10.1088/0004-637x/742/1/2
复制
发表时间：
2011-08
期刊：
影响因子：
--
通讯作者：
M. Steglich;Jordy Bouwman;F. Huisken;Thomas Henning
中科院分区：
文献类型：
--
作者：
M. Steglich;Jordy Bouwman;F. Huisken;Thomas Henning
到目前为止，还没有基于实验室的研究调查了多环芳烃（PAH）物种作为弥漫星际带（DIBs）和2175 Å UV碰撞的潜在载体。我们通过实验和理论技术对两种特定的中/大型多环芳烃（二苯并二苯脲C30H14和六苯并二苯并多环芳烃C42H18）在中性和阳离子状态下的相关性进行了研究。已经证明，足够大的中性多环芳烃混合物可以部分甚至完全解释紫外线的增加。我们研究了星际紫外光子电离这些分子时吸收带是如何改变的。本文的实验研究是通过随后的远紫外照射进行基质分离光谱来实现的。发现主要的影响是紫外吸收带的拓宽，并伴有轻微的红移。然而，在217.5 nm附近完整π -π *吸收结构的位置基本保持不变，这可以解释在不同的视线下观测到的星际碰撞的位置不变性。这有利于将这一特征分配给星际多环芳烃种群。就dib而言，我们的调查和其他研究小组进行的实验室研究都不支持与这类分子的可能联系。相反，有合理的论点认为，中性和单电离的阳离子多环芳烃不能对dib负责。
Up to now, no laboratory-based study has investigated polycyclic aromatic hydrocarbon (PAH) species as potential carriers of both the diffuse interstellar bands (DIBs) and the 2175 Å UV bump. We examined the proposed correlation between these two features by applying experimental and theoretical techniques on two specific medium-sized/large PAHs (dibenzorubicene C30H14 and hexabenzocoronene C42H18) in their neutral and cationic states. It was already shown that mixtures of sufficiently large, neutral PAHs can partly or even completely account for the UV bump. We investigated how the absorption bands are altered upon ionization of these molecules by interstellar UV photons. The experimental studies presented here were realized by performing matrix isolation spectroscopy with subsequent far-UV irradiation. The main effects were found to be a broadening of the absorption bands in the UV combined with slight redshifts. The position of the complete π–π* absorption structure around 217.5 nm, however, remains more or less unchanged, which could explain the observed position invariance of the interstellar bump for different lines of sight. This favors the assignment of this feature to the interstellar PAH population. As far as the DIBs are concerned, neither our investigations nor the laboratory studies carried out by other research groups support a possible connection with this class of molecules. Instead, there are reasonable arguments that neutral and singly ionized cationic PAHs cannot be held responsible for the DIBs.