Fingerprints of polycyclic aromatic hydrocarbons (PAHs) in infrared absorption spectroscopy

• IR spectra of a representative set of PAHs have been simulated with DFT and analyzed with statistical methods.
• Characteristic patterns of the CH out-of-plane bending vibrations have been identified.
• IR signals associated to CH out-of-plane bending have been assigned to the edge topology of PAHs.

We have analyzed a set of 51 PAHs whose structures have been hypothesized from mass spectrometry data collected on samples extracted from carbon particles of combustion origin. We have obtained relationships between infrared absorption signals in the fingerprint region (mid-IR) and the chemical structures of PAHs, thus proving the potential of IR spectroscopy for the characterization of the molecular structure of aromatic combustion products. The results obtained here for the spectroscopic characterization of PAHs can be also of interest in Materials Science and Astrophysics.

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