Giant Infrared Resonances of Cyclocarbon Cations.

Area of Science:

• Physical Chemistry
• Astrochemistry
• Materials Science

Background:

• Carbon clusters of 10-60 atoms predominantly form rings.
• Carbon rings were historically considered transient and detectable only as charged species.
• Recent advancements enable synthesis and imaging of carbon rings, renewing interest in their properties.

Purpose of the Study:

• To investigate the infrared spectroscopic properties of charged cyclocarbons (C4n+, n=5-11).
• To compare the infrared resonances of cyclocarbons with those of fullerenes and bi-ring isomers.
• To explore the implications of these properties for cyclocarbon detection and formation.

Main Methods:

• Acquisition of infrared spectra for charged cyclocarbon species (C4n+, n=5-11).
• Comparison of spectral intensities with fullerene and bi-ring isomers.
• Density functional theory (DFT) calculations to interpret spectral features.

Main Results:

• Charged cyclocarbons display intense infrared resonances between 550-1800 cm-1.
• These resonances are at least 50 times stronger than those of coexisting fullerene and bi-ring isomers.
• DFT calculations link the intense resonances to oscillating Kekulé-type distortions.

Conclusions:

• The intense infrared resonances serve as distinctive spectroscopic signatures for cyclocarbon cations.
• These signatures are valuable for detecting cyclocarbons in diverse environments, including interstellar space.
• Enhanced radiative cooling may promote cyclocarbon formation via bimolecular reactions in low-pressure settings.