The infrared absorption spectrum of phenylacetylene and its deuterated isotopologue
The infrared absorption spectrum of phenylacetylene and its deuterated isotopologue

The infrared absorption spectrum of phenylacetylene and its deuterated isotopologue

Researchers at FELIX and collaborators at NASA have measured the far- and mid-infrared spectrum of phenylacetylene, a molecule recently detected in space, and its deuterated isotopologue. Comparisons with detailed quantum chemical calculations reveal the significance of anharmonicities in these species, beyond simple 2-quanta modes. The article, published at JCP, was highlighted in its front cover.

Anharmonic effects in spectroscopy

When calculating an infrared spectrum from quantum chemistry methods, such as density functional theory, a core assumption is the harmonic approximation. Although such an approximation leads in certain cases to a good agreement with experimental results, it can also fail when describing an infrared spectrum. To remedy this problem, many quantum chemistry software packages allow the computation of “anharmonic effects”, but only for what is known as 2-quanta modes. Researchers at FELIX have shown, by combining gas-phase infrared spectroscopy measurements of the molecule phenylacetylene (recently detected in space), that 2-quanta modes are still an oversimplification of the complex energy surface of carbon-based molecules. Researchers at FELIX have shown, by combining gas-phase infrared spectroscopy measurements of the molecule phenylacetylene (recently detected in space), that 2-quanta modes are still an oversimplification of the complex energy surface of carbon-based molecules.

The infrared absorption spectrum of phenylacetylene and its deuterated isotopologue

Article:

The infrared absorption spectrum of phenylacetylene and its deuterated isotopologue in the mid- to far-IR

Vincent J. Esposito, Piero Ferrari, Wybren Jan Buma, Ryan C. Fortenberry, Christiaan Boersma, Alessandra Candian, Alexander G. G. M. Tielens

J. Chem. Phys. 160, 114312 (2024)

https://doi.org/10.1063/5.0191404

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