Authors
Eli Katz, Heinrich Salzmann, J Mathias Weber, Anne B McCoy
Published in
The journal of physical chemistry. A. Volume 130. Issue 34. Pages 6659-6668. Aug 27, 2026.
Abstract
The CH stretching region of the infrared spectra of polycyclic aromatic hydrocarbon radical anions (2700-3100 cm-1) is characterized by complicated band patterns that defy straightforward assignments from harmonic calculations. We compare experimental infrared photodissociation spectra of argon-tagged anthracene, pyrene, perylene, and fluoranthene anions with spectra computed using different methods in the framework of vibrational perturbation theory, starting from electronic structure calculations based on density functional theory. We trace the complex behavior in the CH stretching region to Fermi interactions between levels with one vibrational quantum of CH stretching excitation and vibrational states with two quanta in lower frequency modes characterized by CH wagging, CC stretching, and CCC bending motions. The resulting vibrational states are strongly mixed in the basis of the harmonic normal modes. Taking all 2:1 Fermi resonances in the relevant frequency range into account typically results in the best agreement between theory and experiment.
PMID:
42679106
Bibliographic data and abstract were imported from PubMed on 02 Sep 2026.
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