Near-threshold shape resonance in the photoionization of 2-butyne

Xu, Haiping; Jacovella, Ugo; Ruščić, Branko; Pratt, S. T.; Lucchese, Robert R.

doi:10.1063/1.3701762

Cited by 23 publications

(47 citation statements)

References 59 publications

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“…78,79 The onset at 8.2 eV as well as the following structures (up to 9.4 eV) could therefore be due to auto-ionizing states of the neutral species at these energies. To our knowledge it is not possible to easily predict such features or to attribute them to one of the three considered isomers.…”

Section: Physical Chemistry Chemical Physics Accepted Manuscriptmentioning

confidence: 99%

Flow tube studies of the C(³P) reactions with ethylene and propylene

Capron

Bourgalais

Kailasanathan

et al. 2015

Phys. Chem. Chem. Phys.

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Product detection studies of C((3)P) atom reactions with ethylene, C2H4(X(1)Ag) and propylene, C3H6(X(1)A') are carried out in a flow tube reactor at 332 K and 4 Torr (553.3 Pa) under multiple collision conditions. Ground state carbon atoms are generated by 193 nm laser photolysis of carbon suboxide, C3O2 in a buffer of helium. Thermalized reaction products are detected using tunable VUV photoionization and time of flight mass spectrometry. For C((3)P) + ethylene, propargyl (C3H3) is detected as the only molecular product in agreement with previous studies on this reaction. The temporal profiles of the detected ions are used to discriminate C((3)P) reaction products from side reaction products. For C((3)P) + propylene, two reaction channels are identified through the detection of methyl (CH3) and propargyl (C3H3) radicals for the first channel and C4H5 for the second one. Franck-Condon Factor simulations are employed to infer the C4H5-isomer distribution. The measured 1 : 4 ratio for the i-C4H5 isomer relative to the methylpropargyl isomers is similar to the C4H5 isomer distribution observed in low-pressure flames and differs from crossed molecular beams data. The accuracy of these isomer distributions is discussed in view of large uncertainties on the photoionization spectra of the pure C4H5 isomers.

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Section: Physical Chemistry Chemical Physics Accepted Manuscriptmentioning

confidence: 99%

Flow tube studies of the C(³P) reactions with ethylene and propylene

Capron

Bourgalais

Kailasanathan

et al. 2015

Phys. Chem. Chem. Phys.

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“…In contrast to CH 3 -(CC) 2 -CH + 3 , which has been well characterised by emission spectroscopy [15,16], the experimental information available on CH 3 -CC-CH + is currently limited to that contained in the He I photoelectron spectrum of CH 3 -CC-CH 3 [17], which was recorded with partial resolution of the vibrational structure. Additional experimental information was obtained by vacuumultraviolet (VUV) photoabsorption [18], photoionisation, and photoelectron spectroscopy of CH 3 -CC-CH 3 in combination with velocity-map imaging of low-energy photoelectrons [19]. These studies have been complemented, in Ref.…”

Section: Please Scroll Down For Articlementioning

confidence: 99%

“…These studies have been complemented, in Ref. [19], by ab initio calculations relying on the composite G3X approach (see Ref. [20]), with a determination of the vibrational frequencies of the cation using B3LYP/6-31G(2df,p) density functional theory.…”

Section: Please Scroll Down For Articlementioning

confidence: 99%

Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH₃–CC–CH⁺₃and CD₃–CC–CD⁺₃

2015

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Pulsed-field-ionisation zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of 2-butyne (CH 3 -CC-CH 3 ) and its fully deuterated isotopomer have been recorded in the region of the origin band of theX + 2 E 1 ←X 1 A 1 ionising transition. The spectral congestion originating from the combined effects of the internal rotation of the methyl groups, the spin-orbit coupling, and the Jahn-Teller effect prevented the full resolution of the rotational structure of the photoelectron spectra. A tentative analysis of the rotational branch structure of the photoelectron spectra using rovibronic photoionisation selection rules derived in the permutation-inversion spin double group G 36 (M 2 ) suggests a splitting of ∼10.5 cm −1 between the two spin-orbit components E 3/2 and E 1/2 of theX + 2 E 1 ground state and an almost free internal rotation of the methyl groups in the cations. Assignments are proposed for several low-lying vibrational levels of the cations.

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“…The spectacularly fast-rising cross section of 2-butyne, attributed to a shape resonance, is discussed in detail by Xu et al 27 In comparison, 1-butyne does not share such a rapid increase but nevertheless bears strong photoionization cross-section values soon after the ionization onset, particularly compared to the butadienes. These four C 4 H 6 isomers have well separated AIEs and the general morphologies of their spectra are markedly different.…”

Section: The M/z 54 Reaction Productmentioning

confidence: 99%

Product Branching Fractions of the CH + Propene Reaction from Synchrotron Photoionization Mass Spectrometry

et al. 2013

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The CH(X2Π) + propene reaction is studied in the gas phase at 298 K and 4 Torr (533.3 Pa) using VUV synchrotron photoionization mass spectrometry. The dominant product channel is the formation of C4H6 (m/z 54) + H. By fitting experimental photoionization spectra to measured spectra of known C4H6 isomers, the following relative branching fractions are obtained: 1,3-butadiene (0.63 ± 0.13), 1,2-butadiene (0.25 ± 0.05), and 1-butyne (0.12 ± 0.03) with no detectable contribution from 2-butyne. The CD + propene reaction is also studied and two product channels are observed that correspond to C4H6 (m/z 54) + D and C4H5D (m/z 55) + H, formed at a ratio of 0.4 (m/z 54) to 1.0 (m/z 55). The D elimination channel forms almost exclusively 1,2-butadiene (0.97 ± 0.20) whereas the H elimination channel leads to the formation of deuterated 1,3-butadiene (0.89 ± 0.18) and 1-butyne (0.11 ± 0.02); photoionization spectra of undeuterated species are used in the fitting of the measured m/z 55 (C4H5D) spectrum. The results are generally consistent with a CH cycloaddition mechanism to the C═C bond of propene, forming 1-methylallyl followed by elimination of a H atom via several competing processes. The direct detection of 1,3-butadiene as a reaction product is an important validation of molecular weight growth schemes implicating the CH + propene reaction, for example, those reported recently for the formation of benzene in the interstellar medium ( Jones, B. M. Proc. Natl. Acad. Sci. U.S. A. 2011, 108, 452−457 ABSTRACTThe CH (X 2 Π) + propene reaction is studied in the gas phase at 298 K and 4 Torr (533.3 Pa) using VUV synchrotron photoionization mass spectrometry. The dominant product channel is the formation of C 4 H 6 (m/z 54) + H. By fitting experimental photoionization spectra to measured spectra of known C 4 H 6 isomers, the following relative branching fractions are obtained: 1,3-butadiene (0.63 ± 0.13), 1,2-butadiene (0.25 ± 0.05) and 1-butyne (0.12 ± 0.03) with no detectable contribution from 2-butyne. The CD + propene reaction is also studied and two product channels are observed that correspond to 2011, 108, 452-457).KEYWORDS: radical, gas-phase, photoionization, synchrotron, propene, methylidyne, mass spectrometry. 3 INTRODUCTIONThe highly reactive methylidyne (CH) radical affects the chemistry of energetic gasphase environments including combustion 1-3 , interplanetary atmospheres 4-6 and the interstellar medium. 7 In order to accurately model these systems, detailed chemical data are needed in the form of reaction rate coefficients and product branching fractions. Our purpose here is to determine total product branching fractions and provide mechanistic details for the CH (X 2 Π) + propene reaction. The present work builds on a series of previous product detection studies of the CH radical with small, unsaturated hydrocarbons: acetylene (C 2 H 2 ), ethylene (C 2 H 4 ), allene (C 3 H 4 , CH 2 CCH 2 ) and propyne (C 3 H 4 , CH 3 CCH). 8 Recent works have also investigated the CH reaction with the carbonyl-conta...

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Near-threshold shape resonance in the photoionization of 2-butyne

Cited by 23 publications

References 59 publications

Flow tube studies of the C(³P) reactions with ethylene and propylene

Flow tube studies of the C(³P) reactions with ethylene and propylene

Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH₃–CC–CH⁺₃and CD₃–CC–CD⁺₃

Product Branching Fractions of the CH + Propene Reaction from Synchrotron Photoionization Mass Spectrometry

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Near-threshold shape resonance in the photoionization of 2-butyne

Cited by 23 publications

References 59 publications

Flow tube studies of the C(3P) reactions with ethylene and propylene

Flow tube studies of the C(3P) reactions with ethylene and propylene

Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH3–CC–CH+3and CD3–CC–CD+3

Product Branching Fractions of the CH + Propene Reaction from Synchrotron Photoionization Mass Spectrometry

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Flow tube studies of the C(³P) reactions with ethylene and propylene

Flow tube studies of the C(³P) reactions with ethylene and propylene

Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH₃–CC–CH⁺₃and CD₃–CC–CD⁺₃