TY - JOUR
T1 - Formation mechanism and spectroscopy of C6H radicals in extreme environments
T2 - A theoretical study
AU - Chin, Chih Hao
AU - Zhu, Tong
AU - Zhang, John Zeng Hui
N1 - Funding Information:
C. H. C. performed the calculations and analysed the data. C. H. C., T. Z. and J. Z. H. Z. co-wrote the paper. This work was supported by the National Natural Science Foundation of China (Grants No. 91641116). We thank the East China Normal University Multifunctional Platform for Innovation (No. 001) for providing us with computer time.
Publisher Copyright:
This journal is © the Owner Societies.
PY - 2019
Y1 - 2019
N2 - This study examined the reaction mechanisms of singlet (rhombic) and triplet (linear) C4 with acetylene by using accurate ab initio CCSD(T)/CBS//B3LYP/6-311G(d,p) calculations followed by a kinetic analysis of various reaction pathways and computations of relative product yields in combustion and planetary atmospheres. These calculations were combined with the Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of reaction rate constants for predicting product-branching ratios, which depend on the collision energy under single-collision conditions. The results demonstrate that the initial reaction begins with the formation of an intermediate3i2 with an entrance barrier of 3.0 kcal mol-1 and an intermediate1i1 without entrance barriers. The product-branching ratios obtained by solving kinetic equations with individual rate constants calculated using the RRKM and variational transition-state theories for determining the collision energies between 5 kcal mol-1 and 25 kcal mol-1 demonstrate that l-C6H + H is the dominant reaction product, whereas HC3C3 + H, l-C6 + H2, c-C6H + H, and c-C6 + H2 are minor products. The electronic absorption spectra of solid neon matrices in the range of 17140-22200 cm-1 were obtained by Maier et al., and the optimized ground and excited state structures of C6H were used to simulate the absorption spectra by one-photon excitation equations. The displaced harmonic oscillator approximation and the Franck-Condon approximation were used to simulate the absorption spectrum of the B2Π ← X2Π transition of C6H. This indicates that the vibronic structures were dominated by one of the six active completely symmetric modes, with v3 being the most crucial.
AB - This study examined the reaction mechanisms of singlet (rhombic) and triplet (linear) C4 with acetylene by using accurate ab initio CCSD(T)/CBS//B3LYP/6-311G(d,p) calculations followed by a kinetic analysis of various reaction pathways and computations of relative product yields in combustion and planetary atmospheres. These calculations were combined with the Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of reaction rate constants for predicting product-branching ratios, which depend on the collision energy under single-collision conditions. The results demonstrate that the initial reaction begins with the formation of an intermediate3i2 with an entrance barrier of 3.0 kcal mol-1 and an intermediate1i1 without entrance barriers. The product-branching ratios obtained by solving kinetic equations with individual rate constants calculated using the RRKM and variational transition-state theories for determining the collision energies between 5 kcal mol-1 and 25 kcal mol-1 demonstrate that l-C6H + H is the dominant reaction product, whereas HC3C3 + H, l-C6 + H2, c-C6H + H, and c-C6 + H2 are minor products. The electronic absorption spectra of solid neon matrices in the range of 17140-22200 cm-1 were obtained by Maier et al., and the optimized ground and excited state structures of C6H were used to simulate the absorption spectra by one-photon excitation equations. The displaced harmonic oscillator approximation and the Franck-Condon approximation were used to simulate the absorption spectrum of the B2Π ← X2Π transition of C6H. This indicates that the vibronic structures were dominated by one of the six active completely symmetric modes, with v3 being the most crucial.
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U2 - 10.1039/c9cp03662h
DO - 10.1039/c9cp03662h
M3 - Article
C2 - 31599891
AN - SCOPUS:85074118359
SN - 1463-9076
VL - 21
SP - 23044
EP - 23055
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 41
ER -