title: Infrared vibrational and electronic transitions in the dibenzopolyacene family.
abstract: We report experimental spectra in the mid-infrared (IR) and near-IR for a series of dibenzoacenes isolated in Ar matrices. The experiments are supported by Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations with both vibrational and electronic transitions studied. For the neutrals, we find good agreement between the experimental and B3LYP and BP86 results for all species studied. The band at about 1440 cm(-1) carries more intensity than in typical PAHs and increases in intensity with the size of the dibenzoacene molecule. For the ions the B3LYP approach fails to yield reasonable IR spectra for most systems and the BP86 approach is used. Electronic transitions dominate the vibrational bands in the mid-IR region for the large dibenzoacene ions. In spite of the very strong electronic transitions, there is still reasonable agreement between theory and experiment for the vibrational band positions. The experimental and theoretical results for the dibenzoacenes are also compared with those for the polyacenes.
authors.affiliation: NASA Ames Research Center, Moffett Field, CA 94035, United States. Electronic address: Andrew.Mattioda@nasa.gov.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Mattioda
authors.affiliation: NASA Ames Research Center, Moffett Field, CA 94035, United States. Electronic address: Charles.W.Bauschlicher@nasa.gov.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Bauschlicher
authors.affiliation: NASA Ames Research Center, Moffett Field, CA 94035, United States.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Bregman
authors.affiliation: NASA Ames Research Center, Moffett Field, CA 94035, United States.
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Hudgins
authors.affiliation: NASA Ames Research Center, Moffett Field, CA 94035, United States.
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Allamandola
authors.affiliation: Carl Sagan Center, SETI Institute, 189 Bernardo Ave., Suite 100, Mountain View, CA 94043, United States. Electronic address: Alessandra.Ricca-1@nasa.gov.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Ricca
mesh_terms: D000465:Algorithms; D002244:Carbon / Q000737:chemistry; D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D007477:Ions; D008962:Models, Theoretical; D009991:Oscillometry; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D012984:Software; D013055:Spectrophotometry, Infrared; D019265:Spectroscopy, Near-Infrared; D013059:Spectrum Analysis, Raman; D013997:Time Factors; D014732:Vibration
chemical_list: D007477:Ions; D011084:Polycyclic Aromatic Hydrocarbons; D002244:Carbon; D006859:Hydrogen
keywords: DFT; Electronic transitions; Infrared spectroscopy; Matrix isolation; Polycyclic aromatic hydrocarbons; Vibrational spectroscopy