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PAH emissions (polycyclic aromatic hydrocarbon emissions) are infrared emissions (spectral lines) from molecular clouds. Polycyclic aromatic hydrocarbons are organic materials with two or more benzene rings. They are hydrocarbons with 50-100 carbon atoms and constitute a pollutant in Earth atmosphere. Star-forming regions can form them and they can be detected by the infrared radiation. They produce emission features at 3.3, 6.2, 7.7, 8.6, and 11.2 micrometers. It is considered likely that PAHs are formed by giant carbon stars.
The term PAH emission is also commonly used regarding activities on Earth that produce PAHs, e.g., in reports on air pollution.