Affiner les résultats

Type de document

Institution

Collection spécifique

Langue

Domaine

Université de Fribourg

Absolute angle-differential cross sections for electron-impact excitation of neon within the first 3.5 eV above threshold

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

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2009, vol. 42, no. 4, p. 044009

Absolute angle-differential cross sections for excitation of neon atoms to the four 2p⁵3s and to selected 2p⁵3p levels have been determined as a function of electron energy up to 3.5 eV above threshold at the scattering angles of 0°, 45°, 90°, 135° and 180°. In addition, the cross sections were recorded as function of scattering angle from 0° to 180° at 18 eV for the 2p⁵3s levels and...

Université de Fribourg

Resonance structure in low-energy electron scattering from OCS

Hoffmann, T. H. ; Hotop, H. ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2008, vol. 41, no. 9, p. 195202

Energy-dependent absolute angle-differential cross sections (θ = 135°) for elastic and vibrationally inelastic electron scattering from OCS molecules have been investigated at high resolution (13 meV). The elastic cross section, reported over the range E= 0.06–20 eV, exhibits a deep Ramsauer–Townsend minimum near 0.55 eV and the π*(1.2 eV) and σ*(3.8 eV) resonances known from...

Université de Fribourg

Absolute cross sections for dissociative electron attachment to HCl, HBr, and their deuterated analogs

Fedor, Juraj ; May, Olivier ; Allan, Michael

In: Physical Review A, 2008, vol. 78, p. 032701

We have measured absolute dissociative electron attachment cross sections for HX and DX (X=Cl and Br) using a trochoidal electron spectrometer equipped with a total ion collection collision chamber, operated both in a field-free passive ion collection mode, and an active ion collection mode, with an extracting electric field. Our results for Br⁻ from HBr are in an excellent...

Université de Fribourg

Absolute angle-differential elastic and vibrational excitation cross sections for electron collisions with tetrahydrofuran

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2007, vol. 40, no. 17, p. 3531

Absolute angle-differential elastic and vibrational excitation cross sections for electron collisions with tetrahydrofuran were measured in the energy range 0.1–20 eV, extending existing measurements to lower energies. The elastic cross sections were measured as a function of scattering angle from 10° to 180° at energies of 2 eV, 6 eV, 10 eV and 20 eV, and as a function of electron energy at...

Université de Fribourg

Threshold phenomena in electron-molecule scattering

Allan, Michael

In: Physica Scripta, 2004, vol. T110, p. 161-165

Absolute differential cross sections were measured at 135° for the elastic and the vibrationally inelastic electron scattering from threshold to 12 eV, with emphasis on the threshold region. In addition, relative dissociative electron attachment spectra were measured from 0.1 to 3.5 eV. Structures of vibrational origin were observed at energies below 1 eV, well below the ²Π shape resonance, in...

Université de Fribourg

Structures in elastic, vibrational, and dissociative electron attachment cross sections in N₂O near threshold

Allan, Michael ; Skalický, Tomás

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2003, vol. 36, no. 16, p. 3397-3409

Absolute differential cross sections were measured at 135° for the elastic and the vibrationally inelastic electron scattering from threshold to 12 eV, with emphasis on the threshold region. In addition, relative dissociative electron attachment spectra were measured from 0.1 to 3.5 eV. Structures of vibrational origin were observed at energies below 1 eV, well below the ²Π shape resonance, in...

Université de Fribourg

Measurement of the elastic and v = 0 → 1 differential electron–N₂ cross sections over a wide angular range

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, no. 20, p. 3655–3672

Absolute differential elastic and vibrational excitation cross sections have been measured for N₂ in the scattering angle ranges starting between 0° and 20° and extending to 180°, at energies between 0.8 and 5 eV. The results agree with many previous measurements, in particular for angles around 90°, but discrepancies were found in some cases for angles close to 0° and 180°. Integral and...

Université de Fribourg

Selectivity in the excitation of Fermi-coupled vibrations in CO₂ by impact of slow electrons

Allan, Michael

In: Physical Review Letters, 2001, vol. 87, no. 3, p. 033201

Improvement of resolution of a gas phase hemispherical electron spectrometer (to 7 meV FWHM) permitted separate measurements of the excitation of each member of the well known Fermi dyad in CO₂ by impact of slow electrons. Absolute differential cross sections at a scattering angle of 135° were measured as a function of electron energy. The excitation was found to be highly selective both via...

Université de Fribourg

Electron spectra for associative detachment in low-energy collisions of Cl⁻ and Br⁻ with H and D

Živanov, Svetlana ; Cížek, M. ; Horáček, J. ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2003, vol. 36, no. 16, p. 3513-3531

Energy spectra of electrons detached in collisions of Cl⁻ and Br⁻ with atomic hydrogen and deuterium have been measured for laboratory frame ion energies between 0.2 and 8.0 eV. Their shapes agree very well with the predictions of nonlocal resonance theory. Both types of structure predicted by the theory are observed. They are the 'v steps', at ro-vibrational thresholds, and the 'S...

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...