کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5376267 1504318 2007 16 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Time-dependent density functional study of the electronic spectra of oligoacenes in the charge states −1, 0, +1, and +2
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
Time-dependent density functional study of the electronic spectra of oligoacenes in the charge states −1, 0, +1, and +2
چکیده انگلیسی
We present a systematic theoretical study of the five smallest oligoacenes (naphthalene, anthracene, tetracene, pentacene, and hexacene) in their anionic, neutral, cationic, and dicationic charge states. We used density functional theory (DFT) to obtain the ground-state optimised geometries, and time-dependent DFT (TD-DFT) to evaluate the electronic absorption spectra. Total-energy differences enabled us to evaluate the electron affinities and first and second ionisation energies, the quasiparticle correction to the HOMO-LUMO energy gap and an estimate of the excitonic effects in the neutral molecules. Electronic absorption spectra have been computed by combining two different implementations of TD-DFT: the frequency-space method to study general trends as a function of charge-state and molecular size for the lowest-lying in-plane long-polarised and short-polarised π → π∗ electronic transitions, and the real-time propagation scheme to obtain the whole photo-absorption cross-section up to the far-UV. Doubly ionised PAHs are found to display strong electronic transitions of π → π∗ character in the near-IR, visible, and near-UV spectral ranges, like their singly charged counterparts. While, as expected, the broad plasmon-like structure with its maximum at about 17-18 eV is relatively insensitive to the charge-state of the molecule, a systematic decrease with increasing positive charge of the absorption cross-section between ∼6 and ∼12 eV is observed for each member of the class.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Physics - Volume 340, Issues 1–3, 9 November 2007, Pages 43-58
نویسندگان
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