Related Experiment Video
Updated: Aug 6, 2026

Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems
Published on: June 23, 2023
Far-infrared spectroscopy of small polycyclic aromatic hydrocarbons
Olivier Pirali1, Nguyen-Thi Van-Oanh, Pascal Parneix
1Laboratoire de Photophysique Moléculaire (membre de la Fédération Lumière Matière), CNRS, Université de Paris-Sud, Bât. 210, F-91405, Orsay Cedex, France.
Abstract:
Both experimental and theoretical spectroscopic studies on small gas phase polycyclic aromatic hydrocarbons in the far-infrared spectral region are reported. The experimental set-up based on thermal emission and Fourier transform far infrared analysis led to the detection of relatively broad vibrational bands, unresolved in rotation, representative of each molecule. Detailed theoretical investigations were performed, including both ab initio calculations and spectral simulations. For the majority of the samples, this study provides the first detection of the vibrational modes associated with the skeleton motions.
Related Concept Videos
Infrared (IR) Spectroscopy: Overview
Different compounds display unique properties due to their...
NMR Spectroscopy of Aromatic Compounds
IR Frequency Region: Fingerprint Region
The...
IR and UV–Vis Spectroscopy of Aldehydes and Ketones
IR Absorption Frequency: Hybridization
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
IR and UV–Vis Spectroscopy of Carboxylic Acids
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...

