PHOTODISSOCIATION OF THE DIACETYLENE DIMER AND IMPLICATIONS FOR HYDROCARBON GROWTH IN TITAN'S ATMOSPHERE
- Department of Chemistry, Wayne State University, Detroit, MI 48202 (United States)
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States)
The surface of Titan is obscured by multiple aerosol layers whose composition and formation mechanism have remained poorly understood. These organic haze layers are believed to arise from photolysis and electron impact triggered chemistry in the dense nitrogen (N{sub 2}) and methane (CH{sub 4}) atmosphere involving highly unsaturated hydrocarbon molecules such as acetylene (HCCH), diacetylene (HCCCCH), and triacetylene (HCCCCCCH). Here we show via laboratory studies combined with electronic structure calculations that the photodissociation of the diacetylene dimer ((HCCCCH){sub 2}) readily initiates atomic hydrogen loss and atomic hydrogen transfer reactions forming two prototypes of resonantly stabilized free radicals, C{sub 4}H{sub 3} and C{sub 8}H{sub 3}, respectively. These structures represent hydrogenated polyynes which can neither be synthesized via traditional photodissociation pathways of the monomer nor via hydrogen addition to the polyynes. The photodissociation dynamics of mixed dimers involving acetylene, diacetylene, and even triacetylene present a novel, hitherto overlooked reaction class and show the potential to synthesize more complex, resonantly stabilized free radicals considered to be major building blocks to polycyclic aromatic hydrocarbons in Titan's low-temperature atmosphere.
- OSTI ID:
- 21448828
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 714; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACETYLENE
AEROSOLS
ALKANES
ALKYNES
AROMATICS
ATMOSPHERES
CHEMICAL REACTIONS
COLLOIDS
DECOMPOSITION
DISPERSIONS
DISSOCIATION
ELECTRONIC STRUCTURE
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HYDROCARBONS
HYDROGEN
HYDROGEN TRANSFER
LEPTONS
METHANE
NITROGEN
NONMETALS
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PLANETARY ATMOSPHERES
PLANETS
POLYCYCLIC AROMATIC HYDROCARBONS
RADICALS
SATELLITES
SOLS