Infrared vibrational and electronic transitions in the dibenzopolyacene family

Authors

Andrew Mattioda, NASA Ames Research CenterFollow
Charles Baushlicher Jr., Carl Sagan Center, SETI Institute
Jonathan Bregman, NASA Ames Research Center
Douglas Hudgins, NASA Ames Research Center
Louis Allamandola, NASA Ames Research Center
Alessandra Ricca, Carl Sagan Center, SETI InstituteFollow

Date of this Version

2014

Citation

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 639–652

Comments

This article is a U.S. government work, and is not subject to copyright in the United States.

Abstract

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.