The ketyl radical in the oxidation of ethyne by atomic oxygen at 300-600 K

Vinckier, Christiaan; Schaekers, Marc; Peeters, Jozef

doi:10.1021/j100249a028

Cited by 45 publications

(44 citation statements)

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“…This mechanism is shown in Table 1. [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] Following Peeters and co-workers, 10,11 we assumed that H + HCCO, reaction 2, occurs on both singlet and triplet surfaces, producing 92% CH 2 (a 1 A 1 ) and 8% CH 2 (X 3 …”

Section: Discussionmentioning

confidence: 99%

Photolysis of Ketene at 193 nm and the Rate Constant for H + HCCO at 297 K

2000

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The 193 nm photolysis of ketene was studied by measuring the amount of atomic hydrogen produced when very dilute ketene/Ar and ketene/H 2 mixtures were irradiated by a single pulse from an ArF excimer laser. Absolute concentrations of atomic hydrogen were monitored over a time interval of 0-2.5 ms by using Lyman-R atomic resonance absorption spectroscopy (ARAS). Four different photodissociation channels of ketene were identified: H 2 CCO + hν gives (a) CH 2 ( 3 B 1 ) + CO; (b) CH 2 ( 1 A 1 ) + CO; (c) HCCO + H; and (d) C 2 O(b 1 Σ + ) + H 2 . The quantum yields for each channel were measured as φ a ) 0.628, φ b ) 0.193, φ c ) 0.107, and φ d ) 0.072, respectively. To explore the secondary chemistry that occurred when using higher pressure H 2 CCO/Ar mixtures, a mechanism was constructed that used well-documented reactions and, for most processes, rate constants that had already been accurately determined. Modeling studies using this mechanism showed the [H] profile to be determined largely by the rate of the reaction H + HCCO f CH 2 + CO. An excellent fit to all of the experimental data was obtained when k 2 ) (1.7 ( 0.3) × 10 -10 cm 3 molecule -1 s -1 .

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Section: Discussionmentioning

confidence: 99%

Photolysis of Ketene at 193 nm and the Rate Constant for H + HCCO at 297 K

2000

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“…HCCO is formed in flames primarily by the oxidation of acetylene. 9,10 It has been observed in laboratory studies by infrared absorption 4 and laserinduced fluorescence spectroscopy. 1,2 Several kinetic studies involving HCCO have appeared recently, with total rate constant measurements reported for reactions with NO, 4-7 NO 2 , 5 O 2 , 5 O, 8 and C 2 H 2 .…”

Section: Introductionmentioning

confidence: 94%

Product Branching Ratio of the HCCO + NO Reaction

Rim

Hershberger

1999

J. Phys. Chem. A

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The reaction of HCCO radicals with NO was studied at room temperature by excimer laser photolysis of ketene precursor molecules followed by infrared absorption spectroscopic detection of CO and CO 2 product molecules. After quantification of product yields and consideration of secondary chemistry, we obtain the following product branching ratios (1σ error bars) at 296 K: 0.12 ( 0.04 for CO 2 + (HCN) and 0.88 ( 0.04 for CO + (HCNO). In addition, we estimate a relative quantum yield for HCCO production in the 193 nm photolysis of CH 2 CO to be 0.17 ( 0.02.

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“…14 Of these reactions, those involving the ketenyl radical, HCCO, play a central role, 14 particularly the rapid reaction of ketenyl with atomic hydrogen, 15,16 which leads to highly reactive CH 17 and CH 2 (ã 1 A 1 ); 18 These radicals are known to undergo rapid reactions with many hydrocarbons, notably C 2 H 2 , [19][20][21][22] leading to higher unsaturated hydrocarbons, which are the building blocks of polycyclic aromatic hydrocarbons. 23,24 In combustion, HCCO is formed mainly by oxidation of ethyne, [25][26][27][28][29] and thought to be removed mainly by reaction with O 2 , H, O, OH, and NO.…”

Section: Introductionmentioning

confidence: 99%

Absolute Rate Coefficient of the HCCO + NO Reaction over the Range T = 297−802 K

et al. 2002

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The absolute rate coefficient of the gas-phase reaction HCCO + NO was experimentally determined for the first time over an extended temperature range, 297-802 K. HCCO radicals were generated by pulsed-laser photolysis of CH 2 CO at 193 nm. Their subsequent decay, under pseudo-first-order conditions, was monitored in real time using a newly developed laser-photofragment/laser-induced fluorescence technique (Carl, S. A.; Sun, Q.; Peeters, J. J. Chem. Phys. 2000, 114, 10332) that involved pulsed-laser photodissociation of HCCO at 266 nm and laser-induced fluorescence at ca. 430 nm of the resulting nascent rotationally excited CH(X 2 Π) photofragment. The rate coefficient of the title reaction was found to exhibit a negative temperature dependence described by k 5 (T) (HCCO+NO) ) (1.6 ( 0.2) × 10 -11 exp(340 ( 30 K/T) cm 3 s -1 molecule -1 (2σ errors). In combination with the recent theoretically determined branching ratios for this reaction of this laboratory (Vereecken, L.; Sumathy, R.; Carl, S. A.; Peeters, J. Chem. Phys. Lett. 2001, 344, 400), the temperature dependencies of the two dominant product channels, HCN + CO 2 and HCNO + CO, may be described by k 5a ) (3.7 ( 0.3) × 10 -10 T -0.72(0.02 exp(200 ( 30 K/T) cm 3 s -1 molecule -1 and k 5b ) (1.4 ( 0.2) × 10 -11 exp(320 ( 30 K/T) cm 3 s -1 molecule -1 , respectively, where the given (2σ) error limits are derived from those of the present experimental work only.

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The ketyl radical in the oxidation of ethyne by atomic oxygen at 300-600 K

Cited by 45 publications

References 2 publications

Photolysis of Ketene at 193 nm and the Rate Constant for H + HCCO at 297 K

Photolysis of Ketene at 193 nm and the Rate Constant for H + HCCO at 297 K

Product Branching Ratio of the HCCO + NO Reaction

Absolute Rate Coefficient of the HCCO + NO Reaction over the Range T = 297−802 K

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