Fragmentation of Valence and Carbon Core Excited and Ionized CH<sub>2</sub>FCF<sub>3</sub> Molecule

Morcelle, V.; Medina, Aline; Ribeiro, Leonardo C.; Prazeres, Ítalo; Marinho, Ricardo R. T.; Arruda, Manuela S.; Mendes, Luiz A. Vieira; Santos, Mabele J.; Tenório, Bruno Nunes Cabral; Rocha, Alexandre B.; Santos, A. C. F.

doi:10.1021/acs.jpca.8b09173

Cited by 13 publications

(24 citation statements)

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“…Tetrafluoroethane, CF 3 CH 2 F, also known as R134a, is a HFC compound widely used as refrigerant in automotive air conditioning, domestic refrigeration systems and aerosol applications. , The R134a molecule has become one of the best substitutes for chlorine-related compounds due to its low GWP value (1430) and an atmospheric lifetime of 13.8 years . That is consequence of the reactivity with hydroxyl radicals (OH • ) found in the troposphere, which leads to smaller atmospheric accumulations.…”

Section: Introductionmentioning

confidence: 99%

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

Pereira‐da‐Silva

Rodrigues

Ramos

et al. 2021

J. Am. Soc. Mass Spectrom.

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In the search for alternatives to chlorine-containing gases, tetrafluoroethane, CF3CH2F (R134a), a widely used refrigerant gas, has been recognized as a promising substitute for dichlorodifluoromethane, CCl2F2 (R12). When R12 is replaced by R134a, the global warming potential drops from 8100 to 1430, the ozone depletion potential changes from 1 to 0, and the atmospheric lifetime decreases from 100 to 14 years. Electron interactions in the gas phase play a fundamental role in the atmospheric sciences. Here, we present a detailed study on electron-driven fragmentation pathways of CF3CH2F, in which we have investigated processes induced by both electron ionization and electron attachment. The measurements allow us to report the ion efficiency curves for ion formation in the energy range of 0 up to 25 eV. For positive ion formation, R134a dissociates into a wide assortment of ions, in which CF3 + is observed as the most abundant out of seven ions with a relative intensity above 2%. The results are supported by quantum chemical calculations based on bound state techniques, electron-impact ionization models, and electron-molecule scattering simulations, showing a good agreement. Moreover, the experimental first ionization potential was found at 13.10 ± 0.17 eV and the second at around 14.25 eV. For negative ion formation, C2F3 – was detected as the only anion formed, above 8.3 eV. This study demonstrates the role of electrons in the dissociation of R134a, which is relevant for an improvement of the refrigeration processes as well as in atmospheric chemistry and plasma sciences.

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Section: Introductionmentioning

confidence: 99%

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

Pereira‐da‐Silva

Rodrigues

Ramos

et al. 2021

J. Am. Soc. Mass Spectrom.

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“…However, the values of the fitting parameters do not affect the conclusions about the KO and SO processes. In addition, the structure around 40 eV is not clearly due to KO process; it is also found in single ionization of SUVA 14 and C 2 Cl 4 28 molecules.…”

Section: Resultsmentioning

confidence: 89%

“…The experimental setup has been described in detail in a previous work. 14 Briefly, the experiments were executed at the D05A -TGM 17 beamline at Laborat orio Nacional de Luz Síncrotron (LNLS) in Campinas, Brazil. The source of EUV and X-ray radiation was a bending magnet that enabled us to work in the photon energy range of 21.21 to 320 eV.…”

Section: Methodsmentioning

confidence: 99%

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Double‐valence photoionization of SUVA134a molecule (CFH₂CF₃)

Morcelle

Medina

Ribeiro

et al. 2021

Rapid Comm Mass Spectrometry

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In this work we investigate the single-photon double ionization of the SUVA 134a (1,1,1,2-tetrafluoroethane) molecule in the energy range from 21.21 to 320 eV. Our experimental data are supported by Thomas' and Samson's models. It is shown that the double photoionization of the SUVA 134a can be expressed as a sum of the so-called shake-off (SO) and the knockout (KO) processes. Methods:The experiments were executed at the TGM beamline at Laborat orio Nacional de Luz Síncrotron in Campinas, Brazil. The source of EUV and X-ray radiation was a bending magnet that enabled us to work in the photon energy range of 21.21 to 320 eV. The spectrometer was devised to collect 100% of the ions with kinetic energies up to 30 eV. The photoelectron-photoion (PEPICO) and photoelectron-photoion-photoion (PE2PICO) coincidence techniques were used in the present work. Results:The ratio of double-to-total photoionization as a function of the photon energy for the SUVA molecule exhibits remarkably similar behavior with other atomic and molecular systems. SO depends on large excess energy above the ionization threshold, enabling the photoelectron to leave the interaction region rather speedily to yield a sudden change in the Coulomb field that the shaken electron feels. The measured asymptotic SO probability is P SO (∞) = 0.09. Conclusions:The present analysis shows that the separation of SO and KO processes relies on the experimental evidence that there is no significant interference between SO and KO. The analysis also shows that the separate formulation of KO and SO presents a factual portrayal of double photoionization.Despite having 50 electrons, SUVA has lower double-to-total photoionization fraction (9%) in comparison, for instance, to argon atoms ($20%), which has 18 electrons. This lower e-e correlation could be attributed to its larger volume, that is, lower electron density. | INTRODUCTIONAt low photon energies (EUV), photo-double ionization of atoms and molecules is a rare event, corresponding to only a small percentage when compared to single ionization. It can take place either directly or indirectly. Photo-double ionization of atoms and molecules by a single photon is a central many-body process. Direct double ionization is portrayed by a single photon absorption by the target followed by the sudden ejection of two electrons, as opposed to sequential or indirect core ionization or excitation followed by a series of Auger decays, or

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“…The experiment has been described in detail previously [4]. Briefly, in our experiment, we make use of coincident detection, in which two or more particles are observed and the interdependencies of their properties can thus be determined.…”

Section: Methodsmentioning

confidence: 99%

Ionization and Fragmentation of a Global Warming Gas by EUV and X-Ray Photons

Morcelle

Medina

Ribeiro

et al. 2019

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An experimental investigation of the processes leading tothe fragmentation of the singly ionized 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3) by EUV and soft X-rays is presented. HFC-134ais taken into consideration as the most convenient replacement for CFC-12 in refrigeration applications due to the fact that it has null ozone depletion factor. Dissociation of the singly ionized HFC-134amolecule was induced by valence, direct and indirect C 1s core photoionization or photoexcitation and the ionic fragments were detected in coincidence (PEPICO mode) with the ejected electrons without energy analysis. The singly ionized parent ion CF4CH2+can be detected even at photon energies above the C 1s threshold.

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Fragmentation of Valence and Carbon Core Excited and Ionized CH₂FCF₃ Molecule

Cited by 13 publications

References 19 publications

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

Double‐valence photoionization of SUVA134a molecule (CFH₂CF₃)

Ionization and Fragmentation of a Global Warming Gas by EUV and X-Ray Photons

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Fragmentation of Valence and Carbon Core Excited and Ionized CH2FCF3 Molecule

Cited by 13 publications

References 19 publications

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

Double‐valence photoionization of SUVA134a molecule (CFH2CF3)

Ionization and Fragmentation of a Global Warming Gas by EUV and X-Ray Photons

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Fragmentation of Valence and Carbon Core Excited and Ionized CH₂FCF₃ Molecule

Double‐valence photoionization of SUVA134a molecule (CFH₂CF₃)