Nascent kinetic energy distributions of the ions produced by electron-impact on the CH3F molecule

Torres, M. Inés; Martı́nez, Roberto; Rayo, M. N. Sanchez; Castaño, Fernando

doi:10.1016/s0009-2614(00)00861-7

Cited by 10 publications

(19 citation statements)

References 24 publications

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“…At the other higher photon energies additional peaks at m/ z = 14, 15, and 32 can be discerned and are assigned to CH 2 + , CH 3 + , and CHF + fragment ions in the mass spectra. In addition, similar to previous electron impact ionization and TPEPICO studies, 21,37 the CF + fragment ions which should involve threebody decomposition can be identified with very weak signal in the mass spectra too. Because of the released kinetic energy in the dissociation, the peak widths of CH 2 F + , CHF + , CH ion.…”

Section: Methodssupporting

confidence: 79%

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH₃F⁺ Ions

2017

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The vacuum ultraviolet (VUV) photoionization and dissociative photoionization of methyl fluoride (CHF) in the 12.2-19.8 eV energy range were investigated by using synchrotron radiation coupled to a double imaging photoelectron photoion coincidence (iPEPICO) spectrometer. The production of several fragment ions including CHF, CHF, CH, and CH as a function of state and internal energy of CHF ions was identified and analyzed, with their individual appearance energies measured through threshold photoelectron spectroscopy. Dynamical information was inferred from electron and ion kinetic energy correlation diagrams measured at chosen fixed photon energies. The detailed mechanisms governing the dissociation of state-selected CHF ions prepared in the XE, AA, and BE low-lying electronic states as well as outside the Franck-Condon region have been inferred based on the present experimental results and existing theoretical calculations. Both the CHF and CH primary fragment ions have three different channels of production from different electronic states of CHF. The spin-orbit splitting states of the F fragment, P and P, in the CH + F dissociation channels were assigned and adiabatically correlate to the XE ground state and the AA electronic state, respectively, with the aid of previous theoretical results. The CHF ions in the high energy part of the XE ground state are unstable and statistically dissociate to the CHF(1A) and H(S) fragments along the potential energy curve of the XE state. The AA electronic state is a repulsive state and exclusively dissociates to the CH(1A') and F(P) fragments. In addition, the CHF, CHF, CH, and CH fragment ions are also produced in the BE state and in the Franck-Condon gap by indirect processes, such as internal conversion or dissociative autoionization.

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Section: Methodssupporting

confidence: 79%

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH₃F⁺ Ions

2017

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“…The CH 3 F molecule can undergo a double ionization at 35.0 ± 0.5 eV and Coulombic repulsion yields CH 3 F 2+ ion fragmentation (Masuoka and Koyano 1991). However, the C + AP is found below this energy, at 28.8 ± 0.5 eV (table 2), and produced with a broad KED extending to 5 eV (Torres et al 2000b). The AP correlates with the formation of the C + ion with channel number 15, where H 2 , H and F appear as their partners, at a thermodynamic calculated energy of 24.26 eV.…”

Section: Excess Energymentioning

confidence: 92%

“…The fragment heats of formation, taken from JANAF tables (JANAF 1985) and other standard data collections (Lide 1992(Lide -1993 have been used to calculate the thermodynamic APs presented in the second column of the table. The fourth and fifth columns of table 2 summarize the KED reported elsewhere (Torres et al 2000b). Heavier ions such as CH 3 F + , CH 2 F + , CHF + and CF + are produced with a low KED of the order of 0.1 eV, matching a thermal distribution.…”

Section: Appearance Potentials (Aps)mentioning

confidence: 97%

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Electron-impact dissociative ionization of the CH₃F molecule

Torres

Martı́nez

Castaño

2002

J. Phys. B: At. Mol. Opt. Phys.

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“…The expected effect has its origin in the TICS decrease with the number of electrons and in the large kinetic energy of the ejected lightweight fragments. In fact it has been shown 21,48 that following the electron impact the lightweight fragments are ejected with much higher kinetic energies than heavier mass ones, and thus special care should be taken to avoid FIG. 3.…”

Section: Ch 3 Fmentioning

confidence: 99%

Evaluation of the computational methods for electron-impact total ionization cross sections: Fluoromethanes as benchmarks

Torres

Martı́nez

Rayo

et al. 2001

The Journal of Chemical Physics

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The experimental electron-impact total ionization cross sections ͑TICSs, ICSs͒ of CF 4 , CHF 3 , CH 2 F 2 , and CH 3 F fluoromethanes reported so far and a new set of data obtained with a linear double focusing time-of-flight mass spectrometer have been compared with the ab initio and ͑semi͒empirical based ICS available methods. TICSs computational methods include: two approximations of the binary-encounter dipole ͑BED͒ referred to hereafter as Kim ͑Kim-BEB͒ and Khare ͑Khare-BEB͒ methods, the Deutsch and Märk ͑DM͒ formalism, also requiring atomic and molecular ab initio information, the modified additivity rule ͑MAR͒, and the Harland and Vallance ͑HV͒ methods, both based on semiempirical or empirical correlations. The molecular ab initio information required by the Kim, Khare, and DM methods has been computed at a variety of quantum chemistry levels, with and without electron correlation and a comprehensive series of basis sets. The general conclusions are summarized as follows: the Kim method yields TICS in excellent agreement with the experimental method; the Khare method provides TICS very close to that of Kim at low electron-impact energies ͑Ͻ100 eV͒, but their Mott and Bethe contributions are noticeably different; in the Kim and Khare approximations the electron correlation methods improve the fittings to the experimental profiles in contrast with the large basis sets, that leads to poorer results; the DM formalism yields TICS profiles with shapes similar to the experimental and the BEB methods, but consistently lower and with the profiles maxima shifted towards lower incident electron energies; the MAR method supplies very good ICS profiles, between those of BEB and DM methods; finally, the empirical HV method provides rather poor fittings concomitant with the simplicity and the few empirical parameters used.

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Nascent kinetic energy distributions of the ions produced by electron-impact on the CH3F molecule

Cited by 10 publications

References 24 publications

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH₃F⁺ Ions

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH₃F⁺ Ions

Electron-impact dissociative ionization of the CH₃F molecule

Evaluation of the computational methods for electron-impact total ionization cross sections: Fluoromethanes as benchmarks

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Nascent kinetic energy distributions of the ions produced by electron-impact on the CH3F molecule

Cited by 10 publications

References 24 publications

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH3F+ Ions

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH3F+ Ions

Electron-impact dissociative ionization of the CH3F molecule

Evaluation of the computational methods for electron-impact total ionization cross sections: Fluoromethanes as benchmarks

Contact Info

Product

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Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH₃F⁺ Ions

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH₃F⁺ Ions

Electron-impact dissociative ionization of the CH₃F molecule