Vacuum Ultraviolet Absorption Spectra of Some Halogen Derivatives of Methane. Correlation of the Spectra<sup>1</sup>

Zobel, Carsten; Duncan, A. B. F.

doi:10.1021/ja01614a084

Cited by 73 publications

(21 citation statements)

References 2 publications

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“…6 upper spectrum). Absorption cross sections have been determined by a number of groups, 13,35,[43][44][45][46][47] and the values shown in Fig. 6 is 261.5 cm -1 .…”

Section: Ivb Cf 2 CLmentioning

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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“…6 upper spectrum). Absorption cross sections have been determined by a number of groups, 13,35,[43][44][45][46][47] and the values shown in Fig. 6 is 261.5 cm -1 .…”

Section: Ivb Cf 2 CLmentioning

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 latter are quently occurring in the organism. It is signifithought to be antibonding in the C-C1 or cant in this respect that certain fluorocarbons are C-Br bonds (17,19). The related U.V.…”

Section: Discussionmentioning

confidence: 99%

On the Hydrogen Bond Breaking Ability of Fluorocarbons Containing Higher Halogens

Paolo¹,

Sándorfy²

1974

Can. J. Chem.

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Infrared measurements show that fluorocarbons containing higher halogens are able to open O—H---O, N—H---N, S—H---S, N—H---O=C, type hydrogen bonds. This is probably due to a competitive mechanism of association consisting in the formation of donor–acceptor complexes. It is suggested that the breaking or perturbation of hydrogen bonds by this mechanism is of importance for the explanation of the anesthetic activity of these compounds.

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“…In order to obtain the thermochemical data, we also need to obtain the IR spectral and kinetic data at high temperatures, adding Correspondence to: T. Tsuboi (e-mail: tsuboi@ynu.ac.jp) An abridged version of this paper was presented at the 22nd Int. Symposium on Shock Waves at London, United Kingdom, from July 18 to 23,1999 to the results for the VUV region (Chou et al 1978, Lacher et al 1950, Zobel and Duncan 1955. These molecules have no emission and absorption spectra at around 3-4 µm.…”

Section: Introductionmentioning

confidence: 92%

Infrared absorption and thermal decomposition of some CFCs

2001

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The spectra of CCl2F2, CHClF2 and CCl3F were observed in the wavelength range 7-13 µm. The decadic molar extinction coefficients were measured and compared with the data calculated in this work and also with the HITRAN database. Using the shock tube technique the emission spectra at high temperature were measured and using these emission spectra the pressure-dependent unimolecular rate constants of thermal decomposition of CCl2F2 and CHClF2 were measured in the temperature range 1200-1900 K and in the density range 10 −5 -10 −4 mol/cm 3 .

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Vacuum Ultraviolet Absorption Spectra of Some Halogen Derivatives of Methane. Correlation of the Spectra¹

Cited by 73 publications

References 2 publications

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

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

On the Hydrogen Bond Breaking Ability of Fluorocarbons Containing Higher Halogens

Infrared absorption and thermal decomposition of some CFCs

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Vacuum Ultraviolet Absorption Spectra of Some Halogen Derivatives of Methane. Correlation of the Spectra1

Cited by 73 publications

References 2 publications

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

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

On the Hydrogen Bond Breaking Ability of Fluorocarbons Containing Higher Halogens

Infrared absorption and thermal decomposition of some CFCs

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Vacuum Ultraviolet Absorption Spectra of Some Halogen Derivatives of Methane. Correlation of the Spectra¹