The detection of benzene in Titan’s atmosphere led to the emergence of polycyclic aromatic hydrocarbons (PAHs) as potential nucleation agents triggering the growth of Titan’s orange-brownish haze layers. However, the fundamental mechanisms leading to the formation of PAHs in Titan’s low-temperature atmosphere have remained elusive. We provide persuasive evidence through laboratory experiments and computations that prototype PAHs like anthracene and phenanthrene (C14H10) are synthesized via barrierless reactions involving naphthyl radicals (C10H7•) with vinylacetylene (CH2=CH–C≡CH) in low-temperature environments. These elementary reactions are rapid, have no entrance barriers, and synthesize anthracene and phenanthrene via van der Waals complexes and submerged barriers. This facile route to anthracene and phenanthrene—potential building blocks to complex PAHs and aerosols in Titan—signifies a critical shift in the perception that PAHs can only be formed under high-temperature conditions, providing a detailed understanding of the chemistry of Titan’s atmosphere by untangling elementary reactions on the most fundamental level.
@article{osti_1603089,
author = {Zhao, Long and Kaiser, Ralf I. and Xu, Bo and Ablikim, Utuq and Ahmed, Musahid and Evseev, Mikhail M. and Bashkirov, Eugene K. and Azyazov, Valeriy N. and Mebel, Alexander M.},
title = {Low-temperature formation of polycyclic aromatic hydrocarbons in Titan’s atmosphere},
annote = {The detection of benzene in Titan’s atmosphere led to the emergence of polycyclic aromatic hydrocarbons (PAHs) as potential nucleation agents triggering the growth of Titan’s orange-brownish haze layers. However, the fundamental mechanisms leading to the formation of PAHs in Titan’s low-temperature atmosphere have remained elusive. We provide persuasive evidence through laboratory experiments and computations that prototype PAHs like anthracene and phenanthrene (C14H10) are synthesized via barrierless reactions involving naphthyl radicals (C10H7•) with vinylacetylene (CH2=CH–C≡CH) in low-temperature environments. These elementary reactions are rapid, have no entrance barriers, and synthesize anthracene and phenanthrene via van der Waals complexes and submerged barriers. This facile route to anthracene and phenanthrene—potential building blocks to complex PAHs and aerosols in Titan—signifies a critical shift in the perception that PAHs can only be formed under high-temperature conditions, providing a detailed understanding of the chemistry of Titan’s atmosphere by untangling elementary reactions on the most fundamental level.},
doi = {10.1038/s41550-018-0585-y},
url = {https://www.osti.gov/biblio/1603089},
journal = {Nature Astronomy},
issn = {ISSN 2397-3366},
number = {12},
volume = {2},
place = {United States},
publisher = {Springer Nature},
year = {2018},
month = {10}}
Univ. of Hawaii at Manoa, Honolulu, HI (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; Ministry of Education and Science of the Russian Federation
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 367, Issue 1889https://doi.org/10.1098/rsta.2008.0233