Reactions of O(3<i>P</i>) with alkynes: The CO and H atom channels

Xing, Guoqiang; Huang, X. T.; Wang, Xuebin; Bersohn, R.

doi:10.1063/1.471902

Cited by 24 publications

(47 citation statements)

References 24 publications

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“…Predominant formation of the methylketenyl isomer of C 3 H 3 O is in agreement with the observations of Kanofsky et al 20 It furthermore supports that the larger H-vs D-atom ratio from O( 3 P) + d 1 -propyne observed by Xing et al 55 is contaminated by H-atom sources other than R1c.…”

Section: Resultssupporting

confidence: 74%

Multiplexed Photoionization Mass Spectrometry Investigation of the O(³P) + Propyne Reaction

et al. 2015

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The reaction of O((3)P) + propyne (C3H4) was investigated at 298 K and 4 Torr using time-resolved multiplexed photoionization mass spectrometry and a synchrotron-generated tunable vacuum ultraviolet light source. The time-resolved mass spectra of the observed products suggest five major channels under our conditions: C2H3 + HCO, CH3 + HCCO, H + CH3CCO, C2H4 + CO, and C2H2 + H2 + CO. The relative branching ratios for these channels were found to be 1.00, (0.35 ± 0.11), (0.18 ± 0.10), (0.73 ± 0.27), and (1.31 ± 0.62). In addition, we observed signals consistent with minor production of C3H3 + OH and H2 + CH2CCO, although we cannot conclusively assign them as direct product channels from O((3)P) + propyne. The direct abstraction mechanism plays only a minor role (≤1%), and we estimate that O((3)P) addition to the central carbon of propyne accounts for 10% of products, with addition to the terminal carbon accounting for the remaining 89%. The isotopologues observed in experiments using d1-propyne (CH3CCD) and analysis of product branching in light of previously computed stationary points on the singlet and triplet potential energy surfaces (PESs) relevant to O((3)P) + propyne suggest that, under our conditions, (84 ± 14)% of the observed product channels from O((3)P) + propyne result from intersystem crossing from the initial triplet PES to the lower-lying singlet PES.

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Section: Resultssupporting

confidence: 74%

Multiplexed Photoionization Mass Spectrometry Investigation of the O(³P) + Propyne Reaction

et al. 2015

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“…8,20,21 In addition, an attempt to detect CH 2 (a 1 A 1 ) emission in collision free experiments failed. 35 Nevertheless, according to the theoretical study reported by Yarkony, 36 ISC can occur likely, while recent quasiclassicaltrajectory surface-hopping (QCT-SH) results reported by Rajak and Maiti 37 suggested that a fraction of about one third of the CH 2 + CO channel (which overall is found to account for 21% of the reaction yield at E c = 39.7 kJ mol À1 ) (see Table 1) originates via ISC leading to singlet CH 2 .…”

Section: à9mentioning

confidence: 95%

Dynamics of the O(3P) + C2H2 reaction from crossed molecular beam experiments with soft electron ionization detection

Leonori

Balucani

Capozza

et al. 2014

Phys. Chem. Chem. Phys.

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The reaction between ground state oxygen atoms, O((3)P), and the acetylene molecule, C2H2, has been investigated in crossed molecular beam experiments with mass-spectrometric detection and time-of-flight analysis at three different collision energies, Ec = 34.4, 41.1 and 54.6 kJ mol(-1). From product angular and velocity distribution measurements of the HCCO and CH2 products in the laboratory frame, product angular and translational energy distributions in the center-of-mass frame were determined. Measurements on the CH2 product were made possible by employing for product detection the recently implemented soft electron-ionization (EI) technique with low-energy, tunable electrons, which has permitted suppressing interference coming from the dissociative ionization of reactants, products and background gases. It has been found that the title reaction leads only to two competing channels: H + HCCO (ketenyl) and CO + CH2 (triplet methylene). The branching ratio of cross sections between the two competing channels has been determined to be σ(HCCO)/[σ(HCCO) + σ(CH2)] = 0.79 ± 0.05, independent of collision energy within the experimental uncertainty. This value is in line with that obtained in the most recent and accurate kinetics determination at room temperature as well as with that predicted from recent theoretical calculations based on statistical rate theory and weak-collision master equation analysis and on dynamics surface-hopping quasiclassical trajectory calculations on-the-fly on coupled triplet/singlet ab initio potential energy surfaces. The firm assessment of the branching ratio as a function of translational energy for this important reaction, besides its fundamental significance, is of considerable relevance for the implementation of theoretical models of hydrocarbon combustion.

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“…The reaction has been investigated extensively in kinetics experiments under different conditions of pressure and temperature (300-800 K) [120][121][122]. Channel (3f), leading to the molecular products C 2 H 4 + CO, was recognised in early kinetics work as the main reaction channel [120,124]. In the kinetics experiments only one or a few of the possible products have been identified and the identity of the primary reaction products and their BR has remained the subject of considerable uncertainty over the years.…”

Section: Reaction O( 3 P) + Ch 2 =C=chmentioning

confidence: 99%

“…The last four channels can only originate from the singlet PES. A VUV LIF study by Xing et al [138] provided information on H, H 2 and CO channels by determining the translational energy distribution of the H product and the internal energy of H 2 and CO. More recently, electronic structure calculations have been reported for this reaction, together with an FTIR determination of the vibrational distribution of the CO product (from channels 5f, 5g, 5l and 5m) [139]. Despite a considerable amount of previous experimental (mostly kinetics) work, a detailed characterisation of the product BRs and of the role of ISC was still lacking.…”

Section: Reaction O( 3 P) + Ch 3 Cchmentioning

confidence: 99%

Reaction dynamics of oxygen atoms with unsaturated hydrocarbons from crossed molecular beam studies: primary products, branching ratios and role of intersystem crossing

Casavecchia

Leonori

Balucani

2015

International Reviews in Physical Chemistry

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We review the progress made in the understanding of the dynamics of the reactions of ground state oxygen atoms, O( 3 P), with unsaturated hydrocarbons (acetylene, ethylene, allene, propyne and propene) which are of great relevance, besides from a fundamental point of view, in combustion chemistry and of interest also in atmosphere-and astro-chemistry. Advances in this area have been made possible by an improved crossed molecular beams (CMBs) instrument with rotating mass spectrometric detection and time-of-flight analysis which features product detection by lowenergy electron soft-ionisation for increased sensitivity and universal detection power. This apparatus offers the capability of identifying virtually all primary reaction channels, characterising the dynamics, and determining the branching ratios (BRs) for these polyatomic multichannel nonadiabatic reactions. The reactive scattering results are rationalised with the assistance of theoretical information from other laboratories on the stationary points and product energetics of the relevant ab initio potential energy surfaces (PESs). For the simpler prototypical systems, such as O( 3 P) + ethylene, detailed comparisons with synergic state-of-the-art quasiclassical trajectory surface-hopping calculations on full dimensional ab initio coupled triplet and singlet PESs have recently been possible. For more complex systems, such as O( 3 P) + propene, comparisons with the results of synergic statistical calculations of BRs on ab initio coupled triplet and singlet PESs, have also been carried out very recently. The combined experimental/theoretical approach has allowed for a better understanding of the mechanism of these reactions. And overall has deepened considerably our understanding of chemical reactivity; in addition, these studies provide an important bridge between CMBs dynamics and thermal kinetics as well as valuable information for improving combustion and astrochemistry models.

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Reactions of O(3P) with alkynes: The CO and H atom channels

Cited by 24 publications

References 24 publications

Multiplexed Photoionization Mass Spectrometry Investigation of the O(³P) + Propyne Reaction

Multiplexed Photoionization Mass Spectrometry Investigation of the O(³P) + Propyne Reaction

Dynamics of the O(3P) + C2H2 reaction from crossed molecular beam experiments with soft electron ionization detection

Reaction dynamics of oxygen atoms with unsaturated hydrocarbons from crossed molecular beam studies: primary products, branching ratios and role of intersystem crossing

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Reactions of O(3P) with alkynes: The CO and H atom channels

Cited by 24 publications

References 24 publications

Multiplexed Photoionization Mass Spectrometry Investigation of the O(3P) + Propyne Reaction

Multiplexed Photoionization Mass Spectrometry Investigation of the O(3P) + Propyne Reaction

Dynamics of the O(3P) + C2H2 reaction from crossed molecular beam experiments with soft electron ionization detection

Reaction dynamics of oxygen atoms with unsaturated hydrocarbons from crossed molecular beam studies: primary products, branching ratios and role of intersystem crossing

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Multiplexed Photoionization Mass Spectrometry Investigation of the O(³P) + Propyne Reaction

Multiplexed Photoionization Mass Spectrometry Investigation of the O(³P) + Propyne Reaction