Coggiola, M. J. and Flicker, W. M. and Mosher, O. A. and Kuppermann, A. (1976) Electron-impact spectroscopy of the fluoroethylenes. Journal of Chemical Physics, 65 (7). pp. 2655-2667. ISSN 0021-9606. http://resolver.caltech.edu/CaltechAUTHORS:COGjcp76
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The electron-impact excitation spectra of the six fluoroethylenes and chlorotrifluoroethylene have been investigated at impact energies of 60, 40, and either 20 or 25 eV, and at scattering angles from 0° to 80°. The energy and angular dependence of the relative differential cross sections was determined for several features in the energy-loss range 0–16 eV. This information was used to identify transitions as either spin forbidden or spin allowed. In each molecule, the lowest observed inelastic transition is a spin-forbidden excitation with maximum intensity between 4.18 and 4.68 eV. The locations of these transitions, which are analogous to the N→T transition in ethylene, can be used to interpret the results of some photochemical electronic energy transfer experiments. A second weak singlet→triplet transition occurs in vinyl fluoride with a maximum intensity at 6.4 eV. The other features observed in the 6–10 eV energy-loss region of these molecules agree well with optical spectra. In particular, the large positive shift in the N→V transition energy of tetrafluoroethylene is confirmed. However, no such shift occurs in the N→V maximum intensity transition energy of chlorotrifluoroethylene (7.80 eV), indicating that the steric resistance to torsion is probably not the cause of the observed shift in tetrafluoroethylene. Transitions to many superexcited states lying above the first ionization potential are observed in each molecule. Using the term value method, many of these transitions, as well as lower-lying ones, are assigned to Rydberg series. The average term values obtained in this study agree well with those determined from other series of molecules.
|Additional Information:||Copyright © 1976 American Institute of Physics. (Received 19 August 1975) Work supported in part by the U.S. Energy Research Development Administration (Contract No. AT(04-3)-767), Report Code CALT-767P4-136. Work performed [by M.G.C.] in partial fulfillment of the requirements for the Ph.D. degree in chemistry at the California Institute of Technology. Arthur Amos Noyes Noyes Laboratory of Chemical Physics, Contribution No. 5158.|
|Subject Keywords:||FLUORINATED ALIPHATIC HYDROCARBONS, ELECTRON–MOLECULE COLLISIONS, ENERGY SPECTRA, EXCITATION|
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|Deposited On:||04 Jun 2008|
|Last Modified:||26 Dec 2012 10:04|
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