NCCN and NCCCCN Formation in Titans Atmosphere: 1. Competing Reactions of Precursor HCCN ( 3 A) with H ( 2 S) and CH 3 ( 2 A)
Date
2004
Authors
Osamura, Yoshihiro
Petrie, Simon
Journal Title
Journal ISSN
Volume Title
Publisher
American Chemical Society
Abstract
Quantum chemical calculations, at the CCSD(T)/aug-cc-PVTZ//B3-LYP/6-311G** level of theory, have been used to characterize stationary points on the C2 H2N and C3H4N potential energy surfaces. Reactions which occur on these surfaces include the processes H (2S) + HCCN (3A″) and CH3 ( 2A″) + HCCN (3A″), which are previously unconsidered but very important potential loss processes for the proposed key intermediate, HCCN (3A″), implicated in the formation of NCCN and NCCCCN within the upper atmosphere of the Saturnian satellite Titan. We find that both H (2S) + HCCN (3A″) and CH3 (2A′) + HCCN (3A″) have exothermic product channels lacking positive activation energy barriers, and thus should occur with high efficiency at the low temperatures (∼200 K) characteristic of Titan's atmosphere. We suggest that the occurrence of these competing reactions poses severe problems for the viability of existing mechanisms of Titanian NCCN and NCCCCN formation.
Description
Keywords
Keywords: Activation energy; Isomers; Mass spectrometry; Mathematical models; Perturbation techniques; Photolysis; Potential energy; Quantum theory; Energy barriers; Kinetic modeling; Quantum chemical calculations; Titanian atmosphere models; Ethylene
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Source
Journal of Physical Chemistry A
Type
Journal article