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Université de Fribourg

Recent research directions in Fribourg: nuclear dynamics in resonances revealed by 2-dimensional EEL spectra, electron collisions with ionic liquids and electronic excitation of pyrimidine

Allan, Michael ; Regeta, Khrystyna ; Gorfinkiel, Jimena D. ; Mašín, Zdeněk ; Grimme, Stefan ; Bannwarth, Christoph

In: The European Physical Journal D, 2016, vol. 70, no. 5, p. 1–7

The article briefly reviews three subjects recently investigated in Fribourg: (i) electron collisions with surfaces of ionic liquids, (ii) two-dimensional (2D) electron energy loss spectra and (iii) resonances in absolute cross sections for electronic excitation of unsaturated compounds. Electron energy loss spectra of four ionic liquids revealed a number of excited states, including triplet...

Université de Fribourg

Coupling of electronic and nuclear motion in a negative ion resonance: Experimental and theoretical study of benzene

Allan, Michael ; Čurík, Roman ; Čársky, Petr

In: The Journal of Chemical Physics, 2019, vol. 151, no. 6, p. 064119

We present calculated and measured elastic and vibrational excitation cross sections in benzene with the objective to assess the reliability of the theoretical method and to shed more light on how the electronic motion of the incoming electron is coupled with the nuclear motion of the vibrations. The calculation employed the discrete momentum representation method which involves solving the...

Université de Fribourg

Dissociative electron attachment and electronic excitation in Fe(CO)5

Allan, Michael ; Lacko, M. ; Papp, P. ; Matejčík, Š. ; Zlatar, Matija ; Fabrikant, Ilya I. ; Kočišek, J. ; Fedor, Juraj

In: Physical Chemistry Chemical Physics, 2018, vol. 20, no. 17, p. 11692–11701

In a combined experimental and theoretical study we characterize dissociative electron attachment (DEA) to, and electronically excited states of, Fe(CO)5. Both are relevant for electron-induced degradation of Fe(CO)5. The strongest DEA channel is cleavage of one metal–ligand bond that leads to production of Fe(CO)4−. High- resolution spectra of Fe(CO)4− reveal fine structures at the...

Université de Fribourg

Absolute angle-differential vibrational excitation cross sections for electron collisions with diacetylene

Allan, Michael ; May, Olivier ; Fedor, Juraj ; Ibănescu, Bogdan C. ; Andric, L.

In: Physical Review A, 2011, vol. 83, p. 052701

Absolute vibrational excitation cross sections were measured for diacetylene (1,3-butadiyne). The selectivity of vibrational excitation reveals detailed information about the shape resonances. Excitation of the C≡C stretch and of double quanta of the C-H bend vibrations reveals a ²Πu resonance at 1 eV (autodetachment width ~30 meV) and a ²Πg resonance at 6.2 eV...

Université de Fribourg

Absolute cross sections for electron collisions with diacetylene: elastic scattering, vibrational excitation and dissociative attachment

Allan, Michael ; May, Olivier ; Fedor, Juraj ; Ibǎnescu, Bogdan C ; Andrić, Lidija ; Winstead, Carl ; McKoy, Vincent

In: Journal of Physics: Conference Series, 2012, vol. 388, no. 5, p. 052082

We present absolute experimental cross sections for elastic scattering, vibrational excitation by electron impact and for dissociative electron attachment to 1,3-butadiyne, as well as calculations of the elastic cross sections.

Université de Fribourg

Absolute angle-differential elastic cross sections for electron collisions with diacetylene

Allan, Michael ; Winstead, C. ; McKoy, V.

In: Physical Review A, 2011, vol. 83, no. 6, p. 062703

We report measured and calculated differential elastic cross sections for collisions of low-energy electrons with diacetylene (1,3-butadiyne). A generally satisfactory agreement between theory and experiment has been found. The calculated cross sections provide interesting insight into the underlying resonant structure.

Université de Fribourg

Electron scattering in Pt(PF₃)₄: Elastic scattering, vibrational, and electronic excitation

Allan, Michael

In: Journal of Chemical Physics, 2011, vol. 134, no. 20, p. 204309

Experimental absolute differential cross sections for elastic scattering, and for vibrational and electronic excitation of Pt(PF₃)₄ by low-energy electrons are presented. The elastic cross sections have a deep angle-dependent Ramsauer-Townsend minimum (Emin = 0.26 eV at θ = 135°). The angular distributions of the elastic cross section at and above 6.5 eV show an...

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

Vibrational excitation of hydrogen fluoride by low-energy electrons: theory and experiment

Cízek, M. ; Horáček, J. ; Allan, Michael ; Fabrikant, I. I. ; Domcke, W.

In: Journal of Physics B: Atomic, Molecular And Optical Physics, 2003, vol. 36, no. 13, p. 2837-2849

Vibrational excitation (VE) of HF by low-energy electrons has been investigated experimentally and theoretically. A new nonlocal resonance model has been constructed based on ab initio calculations of the coupling between a discrete state and continuum states. VE and resonant elastic cross sections have been calculated for a set of initial vibrational states of the molecular target. New...

Université de Fribourg

Vibrational excitation of methane by slow electrons revisited: theoretical and experimental study

Čurík, R ; Čársky, P ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2008, vol. 41, no. 11, p. 115203

We have calculated and measured differential and integral cross sections for vibrationally inelastic scattering of electrons by methane molecules. The calculations were carried out using the discrete momentum representation (DMR) method. We solved the two-channel Lippmann–Schwinger equation in the momentum space. The interaction between the scattered electron and the target molecule is...