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Université de Fribourg

Dissociative electron attachment to Pt(PF₃)₄—a precursor for Focused Electron Beam Induced Processing (FEBIP)

May, Olivier ; Kubala, Dušan ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2012, no. 9, p. 2979-2982

Experimental absolute cross sections for dissociative electron attachment (DEA) to Pt(PF₃)₄ are presented. Fragment anions resulting from the loss of one, two, three and four PF₃ ligands as well as the Pt(PF₃)F⁻ and the F⁻ ions were observed. The parent anion Pt(PF₃)⁻₄ is too short-lived to be detected. The dominant process is loss of one ligand, with a very large cross section...

Université de Fribourg

Disentanglement of triplet and singlet states of azobenzene: direct EELS detection and QMC modeling

Dubecký, M. ; Derian, R. ; Horváthová, L. ; Allan, Michael ; Štich, I.

In: Physical Chemistry Chemical Physics, 2011, vol. 13, p. 20939-20945

Singlet and triplet excited states of trans-azobenzene have been measured in the gas phase by electron energy loss spectroscopy (EELS). In order to interpret the strongly overlapping singlet and triplet bands in the spectra a set of large-scale correlated quantum Monte-Carlo (QMC) simulations was performed. The EELS/QMC combination of methods yields an excellent agreement between theory and...

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

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

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

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

Electron impact excitation of the (4p⁵ 5s) states in krypton: high-resolution electron scattering experiments and B-spline R-matrix calculations

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

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2011, vol. 44, no. 6, p. 065201

In a joint experimental and theoretical effort, we carried out a detailed study of electron impact excitation of the 4p⁵ 5s states of Kr. We present angle-differential cross sections over the entire angular range (0°–180°) for a number of energies in the near-threshold region, as well as energy scans for selected angles. The experimental results are in very satisfactory agreement with...

Université de Fribourg

Absolute cross sections for dissociative electron attachment to HCN and DCN

May, Olivier ; Kubala, D. ; Allan, Michael

In: Physical Review A, 2010, vol. 82, p. 010701

Absolute partial cross sections for the formation of CN⁻ in dissociative electron attachment to HCN and DCN have been measured using a time-of-flight ion spectrometer combined with a trochoidal electron monochromator to be 940pm² for CN⁻/HCN and 340pm² for CN⁻/DCN at peaks of the bands due to the ²Π-shape resonance. The dissociative electron attachment bands were then recorded under...

Université de Fribourg

Absolute dissociative electron attachment cross sections in acetylene and its deuterated analogue

May, Olivier ; Fedor, Juraj ; Allan, Michael

In: Chimia, 2010, vol. 64, no. 3, p. 173-176

An instrument for the measurement of absolute dissociative electron attachment cross sections was constructed and applied to two prototype molecules, acetylene (C₂H₂) and deuterated acetylene (C₂D₂). The isotope effect at the first dissociative electron attachment band at 3 eV was determined-the cross section for C₂D⁻/C₂D₂ is 14.4 times smaller than that for C₂H⁻/C₂H₂. The...

Université de Fribourg

Electron collisions with CO: Elastic and vibrational excitation cross sections

Allan, Michael

In: Physical Review A, 2010, vol. 81, no. 04, p. 042706

Absolute differential elastic and vibrational excitation cross sections up to v=11 were measured for CO in scattering angle ranges extending to 180° at energies between 0.2 and 5 eV (and an elastic measurement at 10 eV). The lowest angles were 0° for inelastic scattering and between 5° and 20° for elastic scattering, depending on energy. Integral cross sections were derived by integrating...