Anisotropy and Size Effects on the Optical Spectra of Polycyclic Aromatic Hydrocarbons

详细信息    查看全文

• 作者：Caterina Cocchi ; Deborah Prezzi ; Alice Ruini ; Marilia J. Caldas ; Elisa Molinari
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：August 21, 2014
• 年：2014
• 卷：118
• 期：33
• 页码：6507-6513
• 全文大小：399K
• ISSN：1520-5215

文摘

The electronic and optical properties of polycyclic aromatic hydrocarbons (PAHs) present a strong dependence on their size and geometry. We tackle this issue by analyzing the spectral features of two prototypical classes of PAHs, belonging to D_6h and D_2h symmetry point groups and related to coronene as multifunctional seed. While the size variation induces an overall red shift of the spectra and a redistribution of the oscillator strength between the main peaks, a lower molecular symmetry is responsible for the appearance of new optical features. Along with broken molecular orbital degeneracies, optical peaks split and dark states are activated in the low-energy part of the spectrum. Supported by a systematic analysis of the composition and the character of the optical transitions, our results contribute in shedding light to the mechanisms responsible for spectral modifications in the visible and near UV absorption bands of medium-size PAHs.