Electron-impact dissociative ionization of the CH<sub>3</sub>F molecule

Torres, M. Inés; Martı́nez, Roberto; Castaño, Fernando

doi:10.1088/0953-4075/35/19/313

Cited by 10 publications

(11 citation statements)

References 29 publications

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“…The dissociation of the CH 3 F + ion has been previously studied by several methods, including electron impact ionization, − ion charge-transfer reaction, photoionization mass spectrometry, ,,− photoelectron photoion coincidence (PEPICO) spectroscopy, and threshold PEPICO (TPEPICO) spectroscopy. , Many fragmentation channels to produce CH 2 F + , CHF + , CF + , CH 3 + , and CH 2 + fragment ions are observed in these experiments. The appearance energy corresponding to the lowest dissociation limit of CH 2 F + + H has been measured to be 13.358 eV .…”

Section: Introductionmentioning

confidence: 99%

CH₃⁺ Formation in the Dissociation of Energy-Selected CH₃F⁺ Studied by Double Imaging Electron/Ion Coincidences

2015

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The dissociation of energy-selected methyl fluoride ion CH3F(+) along the CH3(+) and F formation channel has been investigated in detail in the 12.2-19.8 eV energy range. Three low-lying electronic states of the CH3F(+) ion, X(2)E, A(2)A1, and B(2)E, were prepared and analyzed by the method of double imaging photoelectron photoion coincidence (i(2)PEPICO). Three types of CH3(+) fragment ions corresponding to the dissociation of X(2)E, A(2)A1, and B(2)E electronic states have been observed and identified through their kinetic energy release distribution (KERD) curves, showing that the dissociation of the CH3F(+) ion in the different electronic states along the CH3(+) formation channel is state-specific, even outside of the Franck-Condon region. Highly excited vibrational levels of the X(2)E ground state can be populated through a resonant or near-resonant autoionization process and undergo vibrational predissociation into CH3(+) fragment ions. The A(2)A1 first excited state is repulsive along the F-loss coordinate, and its dissociation is direct and fast. The CH3F(+) ions in the B(2)E excited state first undergo an internal conversion toward the hot cation ground state X(2)E and then statistically dissociate into CH3(+) and F fragments.

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Section: Introductionmentioning

confidence: 99%

CH₃⁺ Formation in the Dissociation of Energy-Selected CH₃F⁺ Studied by Double Imaging Electron/Ion Coincidences

2015

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“…Experimentally, IE a s of halomethanes and radicals and AEs of ion fragments from halomethanes have been measured by electron impact ionization (EI) [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], photoionization mass spectrometry (PIMS) or photoionization efficiency spectroscopy (PIES) , photoelectron spectroscopy (PE) [41][42][43][44][45][46][47][48][49][50][51][52][53], and (threshold) photoelectronphotoion coincidence (TPEPICO) techniques [54][55][56][57][58][59][60][61][62][63][64][65][66][67]. The early results, mainly from EI, PI, and PE studies, have been collected by NIST [68].…”

Section: Introductionmentioning

confidence: 99%

Cations of halogenated methanes: adiabatic ionization energies, potential energy surfaces, and ion fragment appearance energies

Wang

2009

Struct Chem

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The DFT-B3LYP and G3X model chemistry were used to predict the cation structures and energetics of fluorinated, chlorinated, and brominated methanes. Ion-complex structures between methylene cations and HX (X = F, Cl, Br) were found for all H-containing cations, and [CHF-FH] ? , [CF 2 -FH] ? , [CCl 2 -ClH] ? , and [CCl 2 -FH] ? structures are more stable than their normal tetravalent structures. Several cations should also be better described as ion-complex structures between methyl cations and halogen atoms, e.g., [CF 3 -Br] ? . Transition states connecting normal and ion-complex structures were also located, and potential energy diagrams were constructed for decomposition of methane cations and to predict the fragmentation pathways. The G3X energies were used to predict the adiabatic ionization energies (IE a s) and ion fragment appearance energies (AEs) from methanes. Many of the experimental AEs correspond to the energies of transition states instead of the thermodynamic dissociation limits.

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“…Information on electron attachment interactions has been found on several fluoroalkanes, − but to the best of our knowledge, experimental studies on electron interactions with the R134a have not been yet reported. In the low energy regime (<10 eV), it is essential to guarantee that two main conditions are fulfilled: a high electron energy resolution and a sufficient electron current in the interaction region even at energies near zero eV.…”

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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Electron-impact dissociative ionization of the CH₃F molecule

Abstract: Electron-impact dissociative ionization of the CH 3 F molecule has been studied in a double-focusing time-of-flight mass spectrometer. The absolute partial ionization cross sections of the nascent ions, namely CH

Cited by 10 publications

References 29 publications

CH₃⁺ Formation in the Dissociation of Energy-Selected CH₃F⁺ Studied by Double Imaging Electron/Ion Coincidences

CH₃⁺ Formation in the Dissociation of Energy-Selected CH₃F⁺ Studied by Double Imaging Electron/Ion Coincidences

Cations of halogenated methanes: adiabatic ionization energies, potential energy surfaces, and ion fragment appearance energies

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

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Electron-impact dissociative ionization of the CH3F molecule

Abstract: Electron-impact dissociative ionization of the CH 3 F molecule has been studied in a double-focusing time-of-flight mass spectrometer. The absolute partial ionization cross sections of the nascent ions, namely CH

Cited by 10 publications

References 29 publications

CH3+ Formation in the Dissociation of Energy-Selected CH3F+ Studied by Double Imaging Electron/Ion Coincidences

CH3+ Formation in the Dissociation of Energy-Selected CH3F+ Studied by Double Imaging Electron/Ion Coincidences

Cations of halogenated methanes: adiabatic ionization energies, potential energy surfaces, and ion fragment appearance energies

Electron Driven Reactions in Tetrafluoroethane: Positive and Negative Ion Formation

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Product

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Electron-impact dissociative ionization of the CH₃F molecule

CH₃⁺ Formation in the Dissociation of Energy-Selected CH₃F⁺ Studied by Double Imaging Electron/Ion Coincidences

CH₃⁺ Formation in the Dissociation of Energy-Selected CH₃F⁺ Studied by Double Imaging Electron/Ion Coincidences