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Denifl, G.; Muigg, D.; Walker, Isobel C.; Cicman, P.; Matejčík, Štefan; Skalný, J. D.; Stamatovic, A.; Märk, T.D.

doi:10.1023/a:1022857202672

Cited by 26 publications

(32 citation statements)

References 18 publications

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“…The electrons are monochromatized using a standard 180°hemispherical analyzer such that the spread of the electron energy distribution is decreased from about 500 meV to a final energy resolution of about 30 meV FWHM with an electron current of approximately 0.5 nA. 8 Ions formed in the collision region were extracted by a weak penetrating electrostatic field and subsequently analyzed by a quadrupole mass spectrometer with a nominal mass range of 2000 amu. The ions were detected by a channel electron multiplier operated in pulse counting mode.…”

Section: Methodsmentioning

confidence: 99%

Ionization energy studies for ozone and OClO monomers and dimers

Probst¹,

Hermansson²,

Urban³

et al. 2002

The Journal of Chemical Physics

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Electron impact ionization cross sections measured close to threshold are reported for both the monomers and dimers of ozone and OClO using a new high resolution electron impact apparatus. The present appearance energies AE͑O 3 ϩ /O 3 ͒ϭ12.70Ϯ0.02 eV, AE ͑OClO ϩ /OClO͒ϭ10.55Ϯ0.02 and AE͑ClO ϩ /OClOϭ13.37Ϯ0.03 eV derived from the measured ionization cross sections are in excellent agreement with the vertical threshold values determined for these ions by high resolution PES and PIMS photoionization studies. The corresponding appearance energies determined for the dimer ions, 10.10Ϯ0.3 eV for ͑O 3 ͒ 2 ϩ and 9.87Ϯ0.2 eV for ͑OClO͒ 2 ϩ , are both red shifted with respect to the monomer case. The bond energy ͑0.70-0.3ϩ0.5͒ eV of ͑OClO͒ 2 ϩ estimated from these data is similar to that of other dimer ions, whereas the bond energy of ͑O 3 -O 3 ϩ ) with ͑2.55Ϫ0.4ϩ0.6͒ eV is rather large suggesting an unusual structure for the cationic ozone dimer ion. Based on quantum chemical calculations on various levels we are led to the conclusion that the ion produced by ionization of the ozone dimer is no longer a conventional dimer ion where the two monomer units are still present ͑as is the case for the OClO system͒, but rather an ion of form O 2 •••O 4 ϩ or a twisted ring structure of ͑O 6 ͒ ϩ .

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Section: Methodsmentioning

confidence: 99%

Ionization energy studies for ozone and OClO monomers and dimers

Probst¹,

Hermansson²,

Urban³

et al. 2002

The Journal of Chemical Physics

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“…Low-energy electron attachment to CCl 2 F 2 has been studied quite extensively, by both electron swarm ,,− and electron beam methods. ,,− , For work carried out prior to 1997, we refer the reader to the review of Christophorou and Olthoff . The swarm experiments yielded thermal attachment rate coefficients (i.e., equal electron temperature T e and gas temperature T G ) at temperatures close to T = 300 K that scatter over the range (0.7−3.2) × 10 −9 cm 3 s −1 . ,, With rising temperature, the thermal rate coefficients were found to increase with an Arrhenius-type behavior k ( T ) = A exp(− E a /( k B T ) ( k B = Boltzmann constant), yielding an activation energy E a of about 150 meV. , The data of Smith et al were extended to temperatures below 300 K by LeGarrec et al Very recently, Miller et al studied the rate over the broad temperature range 291−1100 K; they obtained an activation energy of 126(20) meV.…”

Section: Introductionmentioning

confidence: 99%

“…DEA yields for anion formation from CCl 2 F 2 have been measured in electron beam experiments at resolutions of (0.05−0.5) eV. ,,− , At energies below about 2.0 eV (essentially only formation of Cl − ), the attachment spectra either showed a single rather broad peak or a combination of a resolution-limited peak close to 0 eV and a broader peak with a maximum in the range 0.6−1.1 eV . Swarm-unfolded data indicated a further maximum around 0.3 eV .…”

Section: Introductionmentioning

confidence: 99%

Low-Energy Electron Attachment to the Dichlorodifluoromethane (CCl₂F₂) Molecule

et al. 2009

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Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl(2)F(2)) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl(-) was measured over the energy range 0.001-1.8 eV at the gas temperature T(G) = 300 K. It exhibits cusp structure at thresholds for vibrational excitation of the nu(3)(a(1)) mode due to interaction with the attachment channels. With reference to the thermal attachment rate coefficient k(T = 300 K) = 2.2(8) x 10(-9) cm(3) s(-1) (fitted average from several data), a new highly resolved absolute attachment cross section for T(G) = 300 K was determined. Partial cross sections for formation of the anions Cl(-), Cl(2)(-), F(-), ClF(-), and CCl(2)F(-) were measured over the range 0-12 eV, using three different electron beam experiments of medium energy resolution. The dependence of the attachment rate coefficient k(T(e);T(G) = 300 K) on electron temperature T(e) was calculated over the range 50-15 000 K, based on a newly constructed total cross section for anion formation at T(G) = 300 K. R-matrix calculations for Cl(-) production have been carried out for comparison with the experimental data. The R-matrix results are in line with the main experimental observations and predict the dependence of the DEA cross section on the initial vibrational level nu(3)() and on the vibrational temperature. Furthermore, the cross section for vibrational excitation of the nu(3) mode has been computed.

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“…However, in any case, the electron capture predominantly leads to dissociation of the studied CFC molecules. Dissociative electron attachment to the CFCl 3 and CF 2 Cl 2 molecules in the gas phase was investigated rather extensively. − …”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Radiation-Induced Degradation of CFCl₃ and CF₂Cl₂ in Noble-Gas Matrixes: An Evidence for “Hot” Ionic Channels in the Solid Phase

2016

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The X-ray-induced transformations of simple chlorofluorocarbons (CFCl and CFCl) in solid noble-gas matrixes (Ne, Ar, Kr, and Xe) at 7 K were studied in order to elucidate basic mechanisms of the radiation-chemical degradation with possible implications for stratospheric and extraterrestrial ice chemistry. The decomposition of parent molecules and formation of products were monitored by FTIR spectroscopy, and the identification was supported by ab initio calculations at the CCSD(T) level. It was shown that the ionic reaction channels were predominating in most cases (except for CFCl/Xe system). The primary radical cations (CFCl and CFCl) are either stabilized in matrixes or undergo fragmentation to yield the corresponding secondary cations (CFCl, CCl, CFCl) and halogen atoms. The probability of fragmentation through different channels demonstrates a remarkable matrix dependence, which was explained by the effect of excess energy resulting from the exothermic positive hole transfer from matrix atoms to freon molecules. A qualitative correlation between "hot" ionic fragmentation at low temperatures and gas-phase ion energetics was found. However, dissociative electron attachment leads to formation of neutral radicals (CFCl or CFCl) and chloride anions. One more possible way of dissociative electron attachment in the case of CFCl is formation of CF and Cl. A general scheme of the radiation-induced processes is proposed.

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Untitled

Cited by 26 publications

References 18 publications

Ionization energy studies for ozone and OClO monomers and dimers

Ionization energy studies for ozone and OClO monomers and dimers

Low-Energy Electron Attachment to the Dichlorodifluoromethane (CCl₂F₂) Molecule

Mechanisms of Radiation-Induced Degradation of CFCl₃ and CF₂Cl₂ in Noble-Gas Matrixes: An Evidence for “Hot” Ionic Channels in the Solid Phase

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Untitled

Cited by 26 publications

References 18 publications

Ionization energy studies for ozone and OClO monomers and dimers

Ionization energy studies for ozone and OClO monomers and dimers

Low-Energy Electron Attachment to the Dichlorodifluoromethane (CCl2F2) Molecule

Mechanisms of Radiation-Induced Degradation of CFCl3 and CF2Cl2 in Noble-Gas Matrixes: An Evidence for “Hot” Ionic Channels in the Solid Phase

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Product

Resources

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Low-Energy Electron Attachment to the Dichlorodifluoromethane (CCl₂F₂) Molecule

Mechanisms of Radiation-Induced Degradation of CFCl₃ and CF₂Cl₂ in Noble-Gas Matrixes: An Evidence for “Hot” Ionic Channels in the Solid Phase