High resolution photoabsorption spectrum of hexafluoro-1,3-butadiene (1,3-C4F6) as studied by vacuum ultraviolet (VUV) synchrotron radiation

Elastic differential cross sections for C₄F₆ isomers in the 1.5-200 eV energy electron impact: similarities with six fluorine containing molecules and evidence of F-atom like scattering

We report absolute elastic differential cross sections for electron interactions with the C4F6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6). The incident electron energy range is 1.5-200 eV, and the scattered electron angular range for the differential measurements varies from 15° to 150°. In all cases the absolute scale of the differential cross section was set using the relative flow technique, with helium as the reference species. Atomic-like behaviour in these scattering systems is shown here for the first time, and is further investigated by comparing the elastic cross sections for the C4F6 isomers with other fluorinated molecules, such as SF6 and CnF6 (n = 2, 3, and 6). We note that for all the six-F containing molecules, the scattering process for electron energies above 30 eV is indistinguishable. Finally, we report results for calculations of elastic differential cross sections for electron scattering from each of these isomers, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements is found to be quite remarkable in all cases.

Electronic excitation to singlet states of 1,3-C4F6, c-C4F6 and 2-C4F6 by electron impact--electron energy-loss spectroscopy and ab initio calculations

We report on the first measurements of the electron impact electronic excitation cross sections for C(4)F(6) isomers, hexafluoro-1,3-butadiene (1,3-C(4)F(6)), hexafluorocyclobutene (c-C(4)F(6)), and hexafluoro-2-butyne (2-C(4)F(6)), measured at 100 eV, 3° scattering angle, while sweeping the energy loss over the range 2.0-15.0 eV. Under these experimental conditions, optically allowed transitions are favored. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. The n = 3 members of the Rydberg series have been assigned converging to the lowest ionization energy limits of the C(4)F(6) isomers and classified according to the magnitude of the quantum defects (δ).