Electron-impact induced light emission from CF2Br2 and CF2H2

Martı́nez, Roberto; Castaño, Fernando; Rayo, M. N. Sanchez; Pereira, R.

doi:10.1016/0301-0104(93)80129-w

Cited by 20 publications

(13 citation statements)

References 69 publications

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“…(3)Our calculated minimum energies are within a limit of 0.1 eV in agreement with the data reported by Martinez et al[7]. The excitation function of CHF at the same wavelength shows above the first threshold two further onsets at impact energies of 27.0 eV and 38.5 eV.…”

supporting

confidence: 81%

“…They concluded that this dissociation channel contributes mainly the continuous radiation in the CHF emission spectrum. This assumption cannot explain the appearance of the same UV emission in our measurement of the CH F emission spectrum which shows exactly the same feature as the emission spectrum measured by Martinez et al [7]. At least there should be one further dissociative channel which leads to the production of CF (A I ) in both compounds.…”

Section: Emission Spectra Following 100 Ev Electron Impactcontrasting

confidence: 35%

“…The dissociation of fluoro-methanes following electron and ion impact as well as photon impact has been subject to several investigations and optical emission spectra in the visible, ultraviolet (UV) and vacuum ultraviolet (VUV) region were examined by various groups [1][2][3][4][5][6][7][8][9][10]. The spectra of all CH V F W -compounds show atomic H, C and F lines and bands of diatomic fragments due to CH, CH> and CF radiation.…”

Section: Introductionmentioning

confidence: 99%

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Absolute and relative emission cross sections for electron impact on CH3F, CH2F2 and CHF3

Keller

Mang

Nikola

et al. 1996

Z Phys D - Atoms, Molecules and Clusters

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supporting

confidence: 81%

Section: Emission Spectra Following 100 Ev Electron Impactcontrasting

confidence: 35%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Absolute and relative emission cross sections for electron impact on CH3F, CH2F2 and CHF3

Keller

Mang

Nikola

et al. 1996

Z Phys D - Atoms, Molecules and Clusters

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“…63 We note that the lifetime of the upper state of the 353 nm band measured in this work, 22.6 ns (Table VIII), is very similar to that of the D' 2 3 Π g ion-pair state measured from the D'−A' band at 290 nm. 11,64 V.E H* (n = 6,5,4,3)…”

Section: Discussionmentioning

confidence: 99%

“…Many groups have measured optical emission spectra from these molecules in an attempt to diagnose the emitters produced following VUV excitation. The excitation sources employed have been an ArF laser operating in the multi-photon mode, 2 high energy electrons, [3][4][5][6][7][8][9][10][11][12] fixedenergy gaseous lamps, 13 microwave discharges 14 and rare gas metastables. 15 Despite the many advantages of using tunable VUV photons from a synchrotron radiation (SR) source for such studies, 1 only one such study, on CF 2 Cl 2 , has been reported.…”

Section: Introductionmentioning

confidence: 99%

Vacuum–ultraviolet absorption and fluorescence spectroscopy of CF2H2, CF2Cl2, and CF2Br2 in the range 8–22 eV

Seccombe

Chim

Tuckett

et al. 2001

The Journal of Chemical Physics

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The vacuum-UV absorption and fluorescence spectroscopy of CF 2 X 2 (X=H,Cl,Br) in the range nm is reported. Tunable vacuum-UV radiation in the range 8-22 eV from synchrotron sources at either Daresbury, UK or BESSY1, Germany is used to excite the titled molecules. Fluorescence excitation spectra, with undispersed detection of the fluorescence, were recorded at Daresbury with a resolution of 0.1 nm. VUV absorption spectra at a resolution of 0.08 nm, and dispersed emission spectra with an optical resolution of 8 nm were recorded at BESSY1. Action spectra, in which the VUV energy is scanned with detection of the fluorescence at a specific wavelength, were also recorded at BESSY1 with a resolution of 0.3 nm ; appearance energies for production of a particular emitting state of a fragment are then obtained. Using the single-bunch mode of BESSY1, lifetimes of all emitting states that fall in the range ca. 3-80 ns have been measured. The peaks in the VUV absorption spectra of CF 2 X 2 are assigned to Rydberg transitions. For CF 2 H 2 below 11 eV, there is good agreement between the absorption and the fluorescence excitation spectra, whereas above 11 eV and for the whole range 8-22 eV for CF 2 Cl 2 and CF 2 Br 2 there is little similarity. This suggests that photodissociation to emitting states of fragment species represent minor channels. In the range 8-15 eV, emission is due mainly to CF 2 Ã 1 B 1 − X 1 A 1 and weakly to CFX Ã 1 A" − X 1 A'. These products form by photodissociation of Rydberg states of CF 2 X 2 , and the thresholds for their production therefore relate to energies of the Rydberg states of the parent molecule. For CF 2 H 2 below 11.8 eV CF 2 Ã 1 B 1 can only form with H 2 , whereas for CF 2 Cl 2 and CF 2 Br 2 it is not possible to say whether the other products are 2X or X 2 . For energies above ca. 15 eV, emission is due to diatomic fragments ; CF B 2 ∆ and A 2 Σ + , CCl A 2 ∆, CH B 2 Σ -and A 2 ∆, Cl 2 and Br 2 D' 2 3 Π g , and possibly CBr A 2 ∆. From their appearance energies, there is evidence that, with the exception of CF B 2 ∆ / CF 2 H 2 where the ground state of HF must form , the excited state of CF, CCl or CH forms in association with three atoms. Our results yield no information whether the three bonds in CF 2 X 2 * break simultaneously or sequentially. We suggest that the anomalous behaviour of CF 2 H 2 , in forming H-H or H-F bonds in unimolecular photofragmentation processes, relates to the small size of the hydrogen atom, and hence the unimportance of steric effects in the tightlyconstrained transition state. In no cases is emission observed from excited states of either the CF 2 X free radical or the parent molecular ion, CF 2 X 2 + .4

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