A Theoretical Study of the Photodissociation Mechanism of Cyanoacetylene in Its Lowest Singlet and Triplet Excited States

Luo, Cheng; Du, Wei-Na; Xue-mei, Duan; Li, Ze-Sheng

doi:10.1086/591486

Cited by 9 publications

(28 citation statements)

References 32 publications

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“…Recent experimental and ab-initio calculations (Silva et al 2009) agree well with theoretical work from Luo et al (2008) and lead to the branching ratios (for bimolecular products only) given in Table A.2. The possible minor production of C 2 + HCN (less than 10%) as well as the production of metastable HC 3 N * * were neglected in this study.…”

Section: A8 Photolysis Of C 3 Hsupporting

confidence: 77%

Photochemistry of C₃H_phydrocarbons in Titan’s stratosphere revisited

Hébrard¹,

Dobrijévic²,

Loison³

et al. 2013

A&A

124

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The description of C 3 hydrocarbon chemistry in current photochemical models of Titan's atmosphere is found to be far from complete. We have carefully investigated the photochemistry involving C 3 H p compounds in the atmosphere of Titan (considering both photolysis and neutral reactions), which considerably impacts the abundances of many other hydrocarbon species (including C 2 compounds). Model results indicate that three species (C 3 , c−C 3 H 2 and C 3 H 3 ) could be abundant enough to be present in the Cassini/INMS data. Because the error bars on predicted C 3 -hydrocarbon abundances are considerably larger than those of the observational data, new experimental and theoretical studies targeting the measurement of low-temperature reaction rate constants and product branching ratios are required to reduce current model uncertainties. In particular, we highlight 30 "key reactions", the uncertainty factors of which should be lowered to improve the quality of photochemical models involving C 3 H p molecules.

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Section: A8 Photolysis Of C 3 Hsupporting

confidence: 77%

Photochemistry of C₃H_phydrocarbons in Titan’s stratosphere revisited

Hébrard¹,

Dobrijévic²,

Loison³

et al. 2013

A&A

124

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“…For cyanoacetylene, the FCI/6-31+G(d) estimates come with small error bars, and one notices an excellent agreement between these values and their CCSDTQ counterparts, a statement holding for the Dunning double-ζ basis set results for which the FCI uncertainties are however larger. Using the CCSDTQ values as references, it appears that the previously obtained CASPT2 estimates 106 are, as expected, too low and that the CC3 transition energies are slightly more accurate than their CCSDT counterparts, although all CC estimates of Table 1 come, for a given basis set, in a very tight energetic window. There is also a very neat agreement between the CC/aVTZ and NEVPT2/aVTZ.…”

Section: Cyanoacetylene Cyanogen and Diacetylenementioning

confidence: 54%

A Mountaineering Strategy to Excited States: Highly-Accurate Energies and Benchmarks for Medium Size Molecules

Loos

Lipparini²,

Boggio‐Pasqua³

et al. 2019

Preprint

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Following our previous work focussing on compounds containing up to 3 non-hydrogen atoms [J. Chem. Theory Comput. 14 (2018) [4360][4361][4362][4363][4364][4365][4366][4367][4368][4369][4370][4371][4372][4373][4374][4375][4376][4377][4378][4379], we present here highly-accurate vertical transition energies obtained for 27 molecules encompassing 4, 5, and 6 non-hydrogen atoms: equation-of-motion coupled cluster theory up to the highest technically possible excitation order for these systems (CC3, EOM-CCSDT, and EOM-CCSDTQ), selected configuration interaction 1 arXiv:1912.04173v2 [physics.chem-ph] 31 Jan 2020 (SCI) calculations (with tens of millions of determinants in the reference space), as well as the multiconfigurational n-electron valence state perturbation theory (NEVPT2) method. All these approaches are applied in combination with diffuse-containing atomic basis sets. For all transitions, we report at least CC3/aug-cc-pVQZ vertical excitation energies as well as CC3/aug-cc-pVTZ oscillator strengths for each dipole-allowed transition. We show that CC3 almost systematically delivers transition energies in agreement with higher-level methods with a typical deviation of ±0.04 eV, except for transitions with a dominant double excitation character where the error is much larger. The present contribution gathers a large, diverse and accurate set of more than 200 highly-accurate transition energies for states of various natures (valence, Rydberg, singlet, triplet, n → π , π → π , . . . ). We use this series of theoretical best estimates to benchmark a series of popular methods for excited state calculations: CIS(D), ADC(2), CC2, STEOM-CCSD, EOM-CCSD, CCSDR(3), CCSDT-3, CC3, as well as NEVPT2. The results of these benchmarks are compared to the available literature data.Although these conclusions agree well with earlier studies, 69-71 they obviously only hold for single excitations, i.e., transitions with %T 1 in the 80-100% range. Therefore, we also recently proposed a set of 20 TBE for transitions exhibiting a significant double-excitation character (i.e., with %T 1 typically below 80%). 72 Unsurprisingly, our results clearly evidenced that the error in CC methods is intimately related to the %T 1 value. For example, for the ES with a significant yet not dominant double excitation character [such as the infamous A g ES of butadiene (%T 1 = 75%)] CC methods including triples deliver rather accurate estimates (MAE of 0.11 eV with CC3 and 0.06 eV with CCSDT), surprisingly outperforming second-order multi-reference schemes such as CASPT2 or the generally robust n-electron valence state perturbation theory (NEVPT2). In contrast, for ES with a dominant double excitation character, e.g., the low-lying (n, n) → (π , π ) excitation in nitrosomethane (%T 1 = 2%), single-reference methods (not including quadruples) have been found to be unsuitable with MAEs of 0.86 and 0.42 eV for CC3 and CCSDT, respectively. In this case, multiconfigurational methods are in practice required to obtain accurate results. 72 A clear limit of ...

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“…C 2 H 3 CN photodissociation is a secondary source of HC 3 N although as the HCN + C 2 H 3 reaction has a small rate constant, the C 2 H 3 CN abundance is lower than in earlier photochemical models so that HC 3 N production by C 2 H 3 CN photodissociation is correspondingly small. The photodissociation of HC 3 N in Titan's atmosphere leads mainly to H + C 3 N (Seki et al, 1996;Luo et al, 2008;Silva et al, 2009), although the photodissociation is thought to be a minor pathway with respect to absorption, leading to metastable HC 3 N ÃÃ formation (Clarke and Ferris, 1995;Seki et al, 1996;Halpern et al, 1988). A new experiment, using the CRESU method, has shown that the experimental rate constant for the C 3 N + CH 4 ?…”

Section: Cyanoacetylene (Hc 3 N)mentioning

confidence: 99%

“…At 193 nm, H + C 3 N products represent the other 30% quantum yield, with the C 2 H + CN products being very minor (Seki et al, 1996). Using theoretical work (Luo et al, 2008;Silva et al, 2009) we can assume that H + C 3 N is always the main bimolecular exit channel, although the C 2 H + CN channel may not be negligible at high energy (below 160 nm).…”

Section: B2 Hc 3 Nmentioning

confidence: 99%

The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan

Loison

Hébrard

Dobrijévic

et al. 2015

Icarus

143

287

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A Theoretical Study of the Photodissociation Mechanism of Cyanoacetylene in Its Lowest Singlet and Triplet Excited States

Cited by 9 publications

References 32 publications

Photochemistry of C₃H_phydrocarbons in Titan’s stratosphere revisited

Photochemistry of C₃H_phydrocarbons in Titan’s stratosphere revisited

A Mountaineering Strategy to Excited States: Highly-Accurate Energies and Benchmarks for Medium Size Molecules

The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan

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A Theoretical Study of the Photodissociation Mechanism of Cyanoacetylene in Its Lowest Singlet and Triplet Excited States

Cited by 9 publications

References 32 publications

Photochemistry of C3Hphydrocarbons in Titan’s stratosphere revisited

Photochemistry of C3Hphydrocarbons in Titan’s stratosphere revisited

A Mountaineering Strategy to Excited States: Highly-Accurate Energies and Benchmarks for Medium Size Molecules

The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan

Contact Info

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Photochemistry of C₃H_phydrocarbons in Titan’s stratosphere revisited

Photochemistry of C₃H_phydrocarbons in Titan’s stratosphere revisited