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Université de Fribourg

Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method

Regeta, Khrystyna ; Bannwarth, Christoph ; Grimme, Stefan ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2015, p. -

The technique of low energy (0–30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0–2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes....

Université de Fribourg

Electron-impact vibrational excitation of cyclopropane

Čurík, R. ; Čársky, P. ; Allan, Michael

In: The Journal of Chemical Physics, 2015, vol. 142, no. 14, p. 144312

We report a very detailed test of the ab initio discrete momentum representation (DMR) method of calculating vibrational excitation of polyatomic molecules by electron impact, by comparison of its results with an extensive set of experimental data, covering the entire range of scattering angles from 10∘ to 180∘ and electron energies from 0.4 to 20 eV. The DMR calculations were carried out by...

Université de Fribourg

Absolute cross sections for electronic excitation of furan by electron impact

Regeta, Khrystyna ; Allan, Michael

In: Physical Review A, 2015, vol. 91, no. 1, p. 012707

We measured differential cross sections for exciting the three lowest electronically excited states in furan, as functions both of electron energy and of scattering angle. Emphasis of the present work is on recording detailed excitation functions, revealing resonances in the excitation process. The cross section for the first triplet state has a shoulder in the first 2 eV above threshold,...

Université de Fribourg

Joint experimental and theoretical study on vibrational excitation cross sections for electron collisions with diacetylene

Čurík, Roman ; Paidarová, Ivana ; Allan, Michael ; Čársky, Petr

In: The Journal of Physical Chemistry A, 2014, vol. 118, no. 41, p. 9734–9744

We have measured and calculated differential and integral cross sections for elastic and vibrationally inelastic electron scattering by diacetylene molecules at electron energies from 0.5 to 20 eV in the whole range of scattering angles from 0 to 180°. The calculations were carried out using the discrete momentum representation method (DMR), which is based on the two-channel Lippmann–Schwinger...

Université de Fribourg

Experimental evidence on the mechanism of dissociative electron attachment to formic acid

Janečková, Radmila ; Kubala, Dušan ; May, Olivier ; Fedor, Juraj ; Allan, Michael

In: Physical Review Letters, 2013, vol. 111, no. 21, p. 213201

Two mechanisms for dissociative electron attachment in HCOOH, the formation of HCOO−+H, were proposed in the literature: (i) via a direct electron attachment into a σ∗ resonance, augmented by dipole binding of the incident electron [G. A. Gallup et al., Phys. Rev. A 79, 042701 (2009)], and (ii) with the 1.8 eV π∗ resonance as a doorway state, linked to the products by...

Université de Fribourg

The electronic structure of TEMPO, its cation and anion

Kubala, D. ; Regeta, K. ; Janečková, R. ; Fedor, Juraj ; Grimme, S. ; Hansen, A. ; Nesvadba, P. ; Allan, Michael

In: Molecular Physics, 2013, p. -

The electronic structure of TEMPO (2,2,6,6-Tetramethylpiperidine-N-oxyl) and its cation and anion were studied experimentally using the electron spectroscopy techniques, dissociative electron attachment (DEA) spectroscopy, electron energy-loss spectroscopy, measurement of elastic and vibrational excitation (VE) cross sections and HeI photoelectron spectroscopy. The experiments were supplemented...

Université de Fribourg

Vibrational excitation of cyclopropane by electron impact: An experimental test of the discrete-momentum-representation theory with density-functional-theory approximation of polarization and correlation

Čurík, R. ; Čársky, P. ; Allan, Michael

In: Physical Review A - Atomic, Molecular and Optical Physics, 2012, vol. 86, no. 6, p. 062709

The discrete-momentum-representation theory with short-range correlation and polarization approximated by local-density-functional theory has been augmented by connecting the short-range potential to an asymptotic polarization tensor. The capacity of this theory to correctly describe the coupling of a free electron with nuclear motion is tested by a detailed comparison of calculated and measured...

Université de Fribourg

Electron scattering from krypton: High-resolution experiments and B-spline R-matrix calculations

Zatsarinny, O. ; Bartschat, K. ; Allan, Michael

In: Journal of Physics: Conference Series, 2012, vol. 388, no. 01, p. 012008

In a joint experimental and theoretical effort, we carried out a detailed study of e-Kr collisions. For elastic scattering and excitation of the 4p⁵5s states, we present total and angle-differential cross sections over the entire angular range (0°-180°) for a number of energies, as well as energy scans for selected angles. The experimental results are in very satisfactory agreement with...

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.