1. The anharmonic quartic force field infrared spectra of three polycyclic aromatic hydrocarbons: naphthalene, anthracene, and tetracene
- Author
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Elena Maltseva, Wybren Jan Buma, Cameron J. Mackie, Xinchuan Huang, Jos Oomens, Alessandra Candian, Annemieke Petrignani, Alexander G. G. M. Tielens, Timothy J. Lee, and Molecular Spectroscopy (HIMS, FNWI)
- Subjects
Anthracene ,010304 chemical physics ,Molecular Structure and Dynamics ,Infrared ,Anharmonicity ,Matrix isolation ,Analytical chemistry ,General Physics and Astronomy ,Infrared spectroscopy ,01 natural sciences ,Molecular physics ,Spectral line ,chemistry.chemical_compound ,Tetracene ,chemistry ,0103 physical sciences ,Fermi resonance ,Physical and Theoretical Chemistry ,010303 astronomy & astrophysics ,Hardware_REGISTER-TRANSFER-LEVELIMPLEMENTATION ,Astrophysics::Galaxy Astrophysics - Abstract
Current efforts to characterize and study interstellar polycyclic aromatic hydrocarbons(PAHs) rely heavily on theoretically predicted infrared (IR) spectra. Generally, such studies use the scaled harmonic frequencies for band positions and double harmonic approximation for intensities of species, and then compare these calculated spectra with experimental spectra obtained under matrix isolation conditions. High-resolution gas-phase experimental spectroscopic studies have recently revealed that the double harmonic approximation is not sufficient for reliable spectra prediction. In this paper, we present the anharmonic theoretical spectra of three PAHs: naphthalene, anthracene, and tetracene, computed with a locally modified version of the SPECTRO program using Cartesian derivatives transformed from Gaussian 09 normal coordinate force constants. Proper treatments of Fermi resonances lead to an impressive improvement on the agreement between the observed and theoretical spectra, especially in the C–H stretching region. All major IR absorption features in the full-scale matrix-isolated spectra, the high-temperature gas-phase spectra, and the most recent high-resolution gas-phase spectra obtained under supersonically cooled molecular beam conditions in the CH-stretching region are assigned.
- Published
- 2015