Photoionization of Propargyl and Bromopropargyl Radicals: A Threshold Photoelectron Spectroscopic Study

Hemberger, Patrick; Lang, Melanie; Noller, Bastian; Fischer, Ingo; Alcaraz, Christian; Miranda, Bárbara K. Cunha de; Garcı́a, Gustavo; Dossmann, Héloïse

doi:10.1021/jp112110j

Cited by 44 publications

(43 citation statements)

References 61 publications

(107 reference statements)

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“…2). Furthermore, the TPE spectrum of the propargyl radical recorded at 3.46 mm above the burner surface fits the intensity and position of the adiabatic ionization energy at 8.70 eV obtained from a Franck-Condon simulation [29] very well and is also in agreement with previous experimental data [30]. Concentration of propargyl radicals directly affects the formation of benzene and phenyl due to the recombination reaction (C 3 H 3 + C 3 H 3 = C 6 H 6 or C 6 H 5 + H) and reaction with the allyl radical (C 3 H 5 ).…”

Section: Combustion Intermediate Speciessupporting

confidence: 88%

Flame structure of a low-pressure laminar premixed and lightly sooting acetylene flame and the effect of ethanol addition

Bierkandt

Kasper

Akyildiz

et al. 2015

Proceedings of the Combustion Institute

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The flame structure of a fuel-rich (ϕ = 2.4), laminar premixed, and lightly sooting acetylene flame at 40 mbar and the influence of ethanol addition on the species pool was investigated. Special emphasis was put on the analysis of important soot precursors like propargyl, benzene, and the polyynes. The mole fractions of more than 50 stable and radical species up to m/z = 170 are obtained experimentally in the flames by molecular-beam mass spectrometry (MBMS) in combination with single-photon ionization (SPI) by vacuum ultraviolet (VUV) radiation from the Advanced Light Source (ALS) in Berkeley, CA, USA. For the neat acetylene flame, successful measurements were performed with a combination of MBMS and imaging photoelectron photoion coincidence spectrometry (iPEPICO) at the VUV beamline at the Swiss Light Source (SLS) in Villigen, Switzerland and add additional species information to the data set. Some interesting isomers (C 3 H 2 , C 4 H 5 , C 4 H 2 O) can be clearly identified by comparison of measured photoionization efficiency (PIE) curves or threshold photoelectron (TPE) spectra with Franck-Condon simulations or literature spectra, respectively. Because of apparatus improvements, the chemical resolution in this study goes beyond prior work and provides a highquality data set for the development of reaction mechanisms at fuel-rich, low-pressure conditions.

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Section: Combustion Intermediate Speciessupporting

confidence: 88%

Flame structure of a low-pressure laminar premixed and lightly sooting acetylene flame and the effect of ethanol addition

Bierkandt

Kasper

Akyildiz

et al. 2015

Proceedings of the Combustion Institute

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“…The resonantly stabilized propargyl radical is the only species responsible for the signal observed at m / z 39. The photoelectron spectrum of propargyl is also displayed in Figure . Indeed, its photoelectron spectrum resembles that of the product detected here very well.…”

Section: Resultssupporting

confidence: 71%

Dissociative Ionization and Thermal Decomposition of Cyclopentanone

Pastoors

Bodi

Hemberger

et al. 2017

Chemistry A European J

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Despite the growing use of renewable and sustainable biofuels in transportation, their combustion chemistry is poorly understood, limiting our efforts to reduce harmful emissions. Here we report on the (dissociative) ionization and the thermal decomposition mechanism of cyclopentanone, studied using imaging photoelectron photoion coincidence spectroscopy. The fragmentation of the ions is dominated by loss of CO, C2H4, and C2H5, leading to daughter ions at m/z 56 and 55. Exploring the C5H8O. + potential energy surface reveals hydrogen tunneling to play an important role in low‐energy decarbonylation and probably also in the ethene‐loss processes, yielding 1‐butene and methylketene cations, respectively. At higher energies, pathways without a reverse barrier open up to oxopropenyl and cyclopropanone cations by ethyl‐radical loss and a second ethene‐loss channel, respectively. A statistical Rice–Ramsperger–Kassel–Marcus model is employed to test the viability of this mechanism. The pyrolysis of cyclopentanone is studied at temperatures ranging from about 800 to 1100 K. Closed‐shell pyrolysis products, namely 1,3‐butadiene, ketene, propyne, allene, and ethene, are identified based on their photoion mass‐selected threshold photoelectron spectrum. Furthermore, reactive radical species such as allyl, propargyl, and methyl are found. A reaction mechanism is derived incorporating both stable and reactive species, which were not predicted in prior computational studies.

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“…The strong band at 8.70 eV corresponds to the adiabatic ionization energy and is in perfect agreement with previous theoretical [26,27] and experimental values. [28,29] For comparison the simulation (red line) based on the Franck-Condon (FC) factors calculated by Botschwina and Oswald is given, [26] which exhibits an excellent agreement with the experimental data. The two small features at 8.83a nd 8.96 eV that originate fromt he pseudosymmetric and pseudoantisymmetric CC stretching vibrationare also well represented.…”

Section: Ms-tpe Spectra Of the Intermediates And Productsmentioning

confidence: 65%

Decomposition of Picolyl Radicals at High Temperature: A Mass Selective Threshold Photoelectron Spectroscopy Study

Reusch

Holzmeier

Gerlach

et al. 2019

Chemistry A European J

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The reactionp roducts of the picolyl radicals at high temperature were characterized by mass-selective threshold photoelectron spectroscopy in the gasp hase. Aminomethylpyridines were pyrolyzedt oi nitiallyp roduce picolyl radicals( m/z = 92). At higher temperatures further thermalr eaction products are generated in the pyrolysis reactor.A ll compoundsw ere identified by mass-selected threshold photoelectron spectroscopya nd severalh itherto unexplored reactive molecules were characterized. The mechanism forseveraldissociation pathways wasoutlined in computations.T he spectrum of m/z = 91, resulting from hydrogen loss of picolyl, shows four isomers, two ethynyl pyr-roles with adiabatic ionizatione nergies (IE ad )o f7 .99 eV (2ethynyl-1H-pyrrole)a nd 8.12 eV (3-ethynyl-1H-pyrrole), and two cyclopentadienec arbonitriles with IE'so f9 .14 eV (cyclopenta-1,3-diene-1-carbonitrile)a nd 9.25eV( cyclopenta-1,4diene-1-carbonitrile). As econd consecutive hydrogen loss forms the cyanocyclopentadienyl radicalw ith IE'so f9 .07 eV (T 0 )a nd 9.21 eV (S 1 ). This compound dissociates further to acetylene and the cyanopropynyl radical (IE = 9.35 eV). Furthermore, the cyclopentadienyl radical, penta-1,3-diyne, cyclopentadiene and propargylw ere identified in the spectra. Computationsi ndicate that dissociation of picolyl proceeds initially via ar esonance-stabilized seven-membered ring.

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Photoionization of Propargyl and Bromopropargyl Radicals: A Threshold Photoelectron Spectroscopic Study

Cited by 44 publications

References 61 publications

Flame structure of a low-pressure laminar premixed and lightly sooting acetylene flame and the effect of ethanol addition

Flame structure of a low-pressure laminar premixed and lightly sooting acetylene flame and the effect of ethanol addition

Dissociative Ionization and Thermal Decomposition of Cyclopentanone

Decomposition of Picolyl Radicals at High Temperature: A Mass Selective Threshold Photoelectron Spectroscopy Study

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