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    Université de Fribourg

    New light on the Kr⁻(4p⁵5s²) Feshbach resonances: high-resolution electron scattering experiments and B-spline R-matrix calculations

    Hoffmann, T. H. ; Ruf, M.-W. ; Hotop, Hartmut ; Zatsarinny, O. ; Bartschat, K. ; Allan, Michael

    In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2010, vol. 43, no. 8, p. 085206

    In a joint experimental and theoretical effort, we carried out a detailed study of electron scattering from Kr atoms in the energy range of the low-lying Kr⁻($4p^5 5s^2$) Feshbach resonances. Absolute angle-differential cross sections for elastic electron scattering were measured over the energy range 9.3–10.3 eV with an energy width of about 13 meV at scattering angles between 10° and...

    Université de Fribourg

    Low-energy electron attachment to the dichlorodifluoromethane (CCl₂F₂) molecule

    Graupner, K. ; Haughey, S. A. ; Field, T. A. ; Mayhew, C. A. ; Hoffmann, T. H. ; May, Olivier ; Fedor, Juraj ; Allan, Michael ; Fabrikant, Ilya I. ; Illenberger, E. ; Braun, M. ; Ruf, M.-W. ; Hotop, Hartmut

    In: The Journal of Physical Chemistry A, 2010, vol. 114, no. 3, p. 1474–1484

    Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl₂F₂) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl⁻ was measured over the energy range 0.001−1.8 eV at the gas...

    Université de Fribourg

    Resonance structure in electron–N₂ scattering around 11.5 eV: high-resolution measurements, ab initio calculations and line shape analyses

    Hoffmann, T. H. ; Allan, Michael ; Franz, K. ; Ruf, M.-W. ; Hotop, Hartmut ; Sauter, G. ; Meyer, W.

    In: Journal of Physics B, 2009, vol. 42, no. 21, p. 215202

    Using two different experimental setups with energy widths of about 6 and 13 meV, we obtained significantly improved results for the energy dependence of angle-differential (10°–180°) elastic and vibrationally inelastic cross sections for electron scattering from N₂ molecules in the energy range around the narrow N⁻₂(R²Σ⁺g) resonance. The energy location and the natural...

    Université de Fribourg

    Effects of interchannel coupling in associative detachment: electron spectra for H+Cl⁻ and H+Br⁻ collisions

    Živanov, Svetlana ; Allan, Michael ; Cížek, M. ; Horáček, J. ; Thiel, F. A. U. ; Hotop, Hartmut

    In: Physical Review Letters, 2002, vol. 89, no. 7, p. 073201

    We present experimental and theoretical energy spectra of the electrons detached in collisions of slow Cl⁻ and Br⁻ ions with atomic hydrogen. Nonlocal resonance theory predicts two kinds of features in the spectra: steplike structures associated with rovibrational onsets and steep rises associated with interchannel coupling, the latter being absent in a calculation using the simpler...

    Université de Fribourg

    Low-energy electron attachment to SF₆ molecules: Vibrational structure in the cross-section for SF₆⁻ formation up to 1 eV

    Braun, M. ; Ruf, M.-W. ; Hotop, Hartmut ; Allan, Michael

    In: Chemical Physics Letters, 2006, vol. 419, p. 517–522

    In high resolution electron attachment to SF₆, cusp structure due to interchannel coupling has been observed in the cross-section for SF₅⁻ formation at the thresholds for vibrational excitation of the SF₆(v₁) mode up to v₁ = 10. It is superimposed on the broad band peaking around 0.55 eV which has been previously attributed to attachment into a repulsive potential...

    Université de Fribourg

    Absolute angle-differential cross sections for electron-impact excitation of neon atoms from threshold to 19.5 eV

    Allan, Michael ; Franz, K. ; Hotop, Hartmut ; Zatsarinny, O. ; Bartschat, K.

    In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2006, vol. 39, p. L139-L144

    Absolute angle-differential cross sections for electron-impact excitation of neon atoms to the four levels with the (2p⁵3s) configuration have been determined both experimentally and theoretically for incident energies from threshold up to 19.5 eV at scattering angles of 135° and 180°. Excellent agreement between the experimental data and theoretical predictions, obtained by a Breit–Pauli...

    Université de Fribourg

    Elastic scattering, vibrational excitation, and attachment in low-energy electron-SF₆ scattering: Experiment and effective range theory

    Fabrikant, Ilya I. ; Hotop, Hartmut ; Allan, Michael

    In: Physical Review A, 2005, vol. 71, p. 022712-22721

    Cross sections at low energies for vibrationally elastic and inelastic scattering, as well as electron attachment to SF₆, have been calculated using a multichannel effective range theory (ERT) with complex boundary conditions. The most active vibrational modes, the totally symmetric mode ν1 and the infrared active mode ν3, have been included in the calculation. The ERT parameters were fitted...