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Université de Fribourg

Absolute cross sections for electronic excitation of pyrimidine by electron impact

Regeta, Khrystyna ; Allan, Michael ; Mašín, Zdeněk ; Gorfinkiel, Jimena D.

In: The Journal of Chemical Physics, 2016, vol. 144, no. 2, p. 024302

We measured differential cross sections for electron-impact electronic excitation of pyrimidine, both as a function of electron energy up to 18 eV, and of scattering angle up to 180°. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. The differential cross sections were summed to obtain integral cross sections. These...

Université de Fribourg

Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory

Regeta, Khrystyna ; Allan, Michael ; Winstead, Carl ; McKoy, Vincent ; Mašín, Zdeněk ; Gorfinkiel, Jimena D.

In: The Journal of Chemical Physics, 2016, vol. 144, no. 2, p. 024301

We measured differential cross sections for elastic (rotationally integrated) electron scattering on pyrimidine, both as a function of angle up to 180∘ at electron energies of 1, 5, 10, and 20 eV and as a function of electron energy in the range 0.1–14 eV. The experimental results are compared to the results of the fixed-nuclei Schwinger variational and R-matrix theoretical methods, which...

Université de Fribourg

The assignment of dissociative electron attachment bands in compounds containing hydroxyl and amino groups

Skalický, Tomás ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2004, vol. 37, p. 4849-4859

Dissociative electron attachment (DEA) spectra were recorded for methanol, phenol, diethylamine, tetramethylhydrazine, piperazine, pyrrole and N,N-dimethylaniline. Comparison with He I photoelectron spectra permitted the assignment of virtually all DEA bands in the saturated compounds to core excited Feshbach resonances with double occupation of Rydberg-like orbitals and various Koopmans' states...

Université de Fribourg

Properties of the π* and σ* states of the chlorobenzene anion determined by electron impact spectroscopy

Skalický, Tomás ; Chollet, Christophe ; Pasquier, Nicolas ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2002, vol. 4, p. 3583 - 3590

The selectivity of vibrational excitation by electron impact has been used to unambiguously assign the negative ion states (resonances) of chlorobenzene and to settle a recent controversy on this subject. The excitation functions of the ring deformation vibrations exhibit bands in the 0.8–1.4 eV range, identifying them as temporary electron captures in the b₁ and...

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

High-resolution experiments and B-spline R-matrix calculations for elastic electron scattering from krypton

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

In: Physical Review A: Atomic, Molecular, and Optical Physics, 2011, vol. 83, no. 3, p. 032713

In a joint experimental and theoretical effort, we carried out a detailed study of elastic electron scattering from Kr atoms. Absolute angle-differential cross sections for elastic electron scattering were measured over the energy range 0.3-9.8 eV with an energy width of about 13 meV at scattering angles between 0° and 180°. Excellent agreement is obtained between our experimental data and...

Université de Fribourg

Dissociative electron attachment and electron energy-loss spectra of phenyl azide

Živanov, Svetlana ; Ibanescu, Bogdan C. ; Paech, M. ; Poffet, Martine ; Baettig, Pio ; Sergenton, A.-C. ; Grimme, S. ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2007, vol. 40, no. 1, p. 101-109

Electron-induced chemistry—dissociative electron attachment (DEA)—was studied for phenyl azide. The major fragment corresponded to the loss of N₂ and formation of the phenylnitrene anion. This process has an onset already at zero kinetic energy of the incident electron and is interpreted as proceeding via the A″π* electronic ground state of the phenyl azide anion. Other fragments,...

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

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

Excited states of Pt(PF₃)₄ andb their role in focused electron beam nanofabrication

Zlatar, Matija ; Allan, Michael ; Fedor, Juraj

In: The Journal of Physical Chemistry C, 2016, vol. 120, no. 19, p. 10667–10674

Electron induced chemistry of metal-containing precursor molecules is central in focused electron beam induced deposition (FEBID). While some elementary processes leading to precursor decomposition were quantitatively characterized, data for neutral dissociation is missing. We provide this data for the model precursor Pt(PF3)4 by using the available cross sections for electronic excitation...