title: The anharmonic quartic force field infrared spectra of three polycyclic aromatic hydrocarbons: Naphthalene, anthracene, and tetracene.
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.
authors.affiliation: Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands.
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Mackie
authors.affiliation: Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Candian
authors.affiliation: SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, California 94043, USA.
authors.forename: Xinchuan
authors.initials: X
authors.lastname: Huang
authors.affiliation: University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Elena
authors.initials: E
authors.lastname: Maltseva
authors.affiliation: Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands.
authors.forename: Annemieke
authors.initials: A
authors.lastname: Petrignani
authors.affiliation: Radboud University, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.affiliation: University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Wybren Jan
authors.initials: WJ
authors.lastname: Buma
authors.affiliation: NASA Ames Research Center, Moffett Field, California 94035-1000, USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Lee
authors.affiliation: Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands.
authors.forename: Alexander G G M
authors.initials: AG
authors.lastname: Tielens