[CF2Cl-], Chlorodifluoromethide ion. Capture of an elusive species

Burton, Donald J.; Wheaton, Gregory A.

doi:10.1021/ja00828a055

Cited by 20 publications

(6 citation statements)

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“…From electron impact measurements, it has been suggested that the breaking of the C-F bond is the main process leaving an excited CF 2 Clfragment 23,24 which may further decompose into Cl -, F -, and CF -. 23 This picture is supported by the gasphase DA data showing a weak CF 2 Clsignal concentrated at the lower energy part of the second resonance.…”

Section: Resultsmentioning

confidence: 99%

Dissociative Electron Attachment to Gas- and Condensed-Phase CF₃Cl: Anion Desorption and Trapping

Weik¹,

Illenberger²,

Nagesha³

et al. 1998

J. Phys. Chem. B

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The interaction of electrons in the energy range from near zero to 10 eV with CF3Cl physisorbed on a Kr surface is studied and compared with previous gas-phase experiments on isolated molecules and CF3Cl clusters. In the gas phase CF3Cl shows resonances in the dissociative attachment (DA) cross section at 1.4 eV, near 4−5 eV, and at 9 eV with the 1.4 eV feature assigned as a single particle resonance with a strong C−Cl repulsive nature. From adsorbed CF3Cl, we observe desorption of Cl- and F- with resonances in the cross section which can be correlated to the gas-phase DA features. Despite its antibonding nature, Cl- desorption via the single particle resonance is very weak, indicating that direct desorption processes do not occur; i.e., orientations of the molecule with the C−Cl axis pointing away from the surface can be excluded, and desorption is always preceded by postdissociation interactions. Charge trapping is virtually restricted to the low-energy resonance. Its maximum is at 0.8 eV and reflects the energy shift of the transient ion due to solvation. The absolute trapping cross section is 43 × 10-18 cm2, exceeding the gas-phase DA value by about 1 order of magnitude. The behavior of the low-energy resonance is described in terms of one-dimensional potential energy curves previously used to model temperature effects in DA to gas-phase CF3Cl, with the anionic curve shifted by the solvation energy. It is shown that autodetachment, which is by far the dominant decay channel in the gas phase, is substantially suppressed in the condensed phase.

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Section: Resultsmentioning

confidence: 99%

Dissociative Electron Attachment to Gas- and Condensed-Phase CF₃Cl: Anion Desorption and Trapping

Weik¹,

Illenberger²,

Nagesha³

et al. 1998

J. Phys. Chem. B

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“…Low-energy secondary photoelectrons can attach to the adsorbed CF 3 Cl molecules to form a negative CF 3 Cl *− ion if the energy and incident direction of the electron upon a CF 3 Cl molecule is in the range for a negative-ion resonance. 47 The negative ion at the surface can then either reemit the electron ͑autodetachment͒ and be quenched by the surface or dissociate to produce one excited CF 2 Cl *− and one neutral F fragment, [48][49][50] e − + CF 3 Cl → CF 3 Cl *− → CF 2 Cl *− + F ͑DA: step 1͒, where a F atom will desorb from the surface for the case of a C-F bond oriented away from the surface or react with surface silicon atom to form surface SiF if the C-F bond is pointing toward the surface. The excited CF 2 Cl *− may further decay according to 48,50…”

Section: Photon-exposure Dependences Of the F − And F + Yields From Tmentioning

confidence: 99%

Continuous-time core-level photon-stimulated desorption spectroscopy for monitoring soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface

Chou

Wen

2006

Phys. Rev. B

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Continuous-time core-level photon-stimulated desorption ͑PSD͒ spectroscopy was proposed for monitoring the soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface. Monochromatic synchrotron radiation was used as a soft x-ray light source in the photon-induced reactions of CF 3 Cl adsorbed on a Si͑111͒-7 ϫ 7 surface at 30 K and also as a probe for studying the produced fluorination states of the bonding surface Si atom in the positive-ion PSD spectroscopy. The F + PSD spectrum was obtained by monitoring the F + signal as a function of incident photon energy near the Si͑2p͒ edge ͑98-110 eV͒. Sequential F + PSD spectra were measured as a function of photon exposure at four adsorbate coverages ͑the first dose= 0.3ϫ 10 15 molecules/ cm 2 , the second dose= 0.8ϫ 10 15 molecules/ cm 2 , the third dose= 2.2 ϫ 10 15 molecules/ cm 2 , and the fourth dose= 3.2ϫ 10 15 molecules/ cm 2 ͒. For the first and second CF 3 Cl-dosed surfaces, the sequential F + PSD spectra show the variation of their shapes with photon exposure and indicate the formation of surface SiF species. The sequential F + PSD spectra for the third and fourth CF 3 Cl-dosed surfaces also show the variation of their shapes with photon exposure and depict the production of surface SiF and SiF 3 species.

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“…This feature was attributed to an excited resonance resulting in a precursor (CF 3 Cl)* Ϫ ion which then followed by sequential dissociation with the cleavage of a C-F bond and leaving an electronically excited (CF 2 Cl)* Ϫ fragment as the first step [57][58][59] ͑ CF 3 Cl͒* Ϫ ͑ 4.1 eV͒→͑CF 2 Cl͒* Ϫ ϩF ͑DA: step 1).…”

Section: Dissociative Attachment On Cf 3 CL Of Photoelectrons Emitmentioning

confidence: 99%

“…The electronically excited (CF 2 Cl)* Ϫ may further decay according to 57,59 ͑ CF 2 Cl͒* Ϫ →CFClϩF Ϫ ͑ DA: step 2 ͒.…”

Section: Dissociative Attachment On Cf 3 CL Of Photoelectrons Emitmentioning

confidence: 99%

Photon-stimulated desorption of F− ions from CF3Cl adsorbed on Si(111)-7×7

Wen

Chou

2004

The Journal of Chemical Physics

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We report the photon-stimulated desorption of negative ions induced by direct dipolar dissociation and dissociative electron attachment. The photon-stimulated desorption of F(-) ions from CF(3)Cl physisorbed on a Si(111)-7x7 surface at 30 K in the photon energy range 12-35 eV was studied. The F(-) ion yield exhibits four resonances, at 12.8, 16.2, 19.5, and 22.3 eV, quite unlike the gas phase photodissociation cross section. The intensities of these resonances depend strongly on the CF(3)Cl coverage in a manner which varies from peak to peak. The resonances at 19.5 and 22.3 eV, which have a significant enhancement in the monolayer regime, are due to electron mediated dipolar dissociation of adsorbed CF(3)Cl molecules. The enhancement is attributed to surface electron attachment following molecular excitation. A significant enhancement in the monolayer regime has also been observed for the resonances at 12.8 and 16.2 eV. These two resonances are ascribable to a combination of electron mediated dipolar dissociation and dissociative electron attachment driven by photoelectrons generated in the neighboring molecules.

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[CF2Cl-], Chlorodifluoromethide ion. Capture of an elusive species

Cited by 20 publications

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Dissociative Electron Attachment to Gas- and Condensed-Phase CF₃Cl: Anion Desorption and Trapping

Dissociative Electron Attachment to Gas- and Condensed-Phase CF₃Cl: Anion Desorption and Trapping

Continuous-time core-level photon-stimulated desorption spectroscopy for monitoring soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface

Photon-stimulated desorption of F− ions from CF3Cl adsorbed on Si(111)-7×7

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[CF2Cl-], Chlorodifluoromethide ion. Capture of an elusive species

Cited by 20 publications

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Dissociative Electron Attachment to Gas- and Condensed-Phase CF3Cl: Anion Desorption and Trapping

Dissociative Electron Attachment to Gas- and Condensed-Phase CF3Cl: Anion Desorption and Trapping

Continuous-time core-level photon-stimulated desorption spectroscopy for monitoring soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface

Photon-stimulated desorption of F− ions from CF3Cl adsorbed on Si(111)-7×7

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Dissociative Electron Attachment to Gas- and Condensed-Phase CF₃Cl: Anion Desorption and Trapping

Dissociative Electron Attachment to Gas- and Condensed-Phase CF₃Cl: Anion Desorption and Trapping