Systematic Shifts in the Ultra-Violet Absorption Spectra of Polycyclic Aromatic Hydrocarbons

Nature ◽  
1952 ◽  
Vol 169 (4305) ◽  
pp. 743-744
Author(s):  
W. F. MADDAMS
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Absorption Spectra ◽  
Aromatic Hydrocarbons ◽  
Ultra Violet ◽  
Polycyclic Aromatic

scholarly journals High-resolution IR absorption spectroscopy of polycyclic aromatic hydrocarbons in the 3 μm region: role of hydrogenation and alkylation

2018 ◽  
Vol 610 ◽  
pp. A65 ◽  
Author(s):  
Elena Maltseva ◽  
Cameron J. Mackie ◽  
Alessandra Candian ◽  
Annemieke Petrignani ◽  
Xinchuan Huang ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
High Resolution ◽  
Absorption Spectra ◽  
Aromatic Hydrocarbons ◽  
Dominant Role ◽  
Selective Absorption ◽  
Ir Absorption ◽  
Spectroscopic Techniques ◽  
High Resolution Data ◽  
Polycyclic Aromatic

Aim. We aim to elucidate the spectral changes in the 3 μm region that result from chemical changes in the molecular periphery of polycyclic aromatic hydrocarbons (PAHs) with extra hydrogens (H-PAHs) and methyl groups (Me-PAHs). Methods. Advanced laser spectroscopic techniques combined with mass spectrometry were applied on supersonically cooled 1,2,3,4-tetrahydronaphthalene, 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, 1,2,3,6,7,8-hexahydropyrene, 9-methylanthracene, and 9,10-dimethylanthracene, allowing us to record mass-selective and conformationally selective absorption spectra of the aromatic, aliphatic, and alkyl CH-stretches in the 3.175 − 3.636 µm region with laser-limited resolution. We compared the experimental absorption spectra with standard harmonic calculations and with second-order vibrational perturbation theory anharmonic calculations that use the SPECTRO program for treating resonances. Results. We show that anharmonicity plays an important if not dominant role, affecting not only aromatic, but also aliphatic and alkyl CH-stretch vibrations. The experimental high-resolution data lead to the conclusion that the variation in Me- and H-PAHs composition might well account for the observed variations in the 3 μm emission spectra of carbon-rich and star-forming regions. Our laboratory studies also suggest that heavily hydrogenated PAHs form a significant fraction of the carriers of IR emission in regions in which an anomalously strong 3 μm plateau is observed.

scholarly journals Calculation of vibrationally resolved absorption spectra of acenes and pyrene

2019 ◽  
Vol 21 (37) ◽  
pp. 21094-21103 ◽  
Author(s):  
Isaac Benkyi ◽  
Enrico Tapavicza ◽  
Heike Fliegl ◽  
Dage Sundholm
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Absorption Spectra ◽  
Excited States ◽  
Aromatic Hydrocarbons ◽  
Function Method ◽  
Electronic Excitation ◽  
Excitation Energies ◽  
Polycyclic Aromatic ◽  
Vibrational Energies ◽  
P Absorption

Absorption spectra of polycyclic aromatic hydrocarbons have been simulated by using a real-time generating function method that combines adiabatic electronic excitation energies with vibrational energies of the excited states.

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