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Université de Fribourg

Treatment of the multimode Jahn–Teller problem in small aromatic radicals

Gruden-Pavlović, Maja ; Garcia-Fernandez, Pablo ; Andjelkovic, Ljubica ; Daul, Claude A. ; Zlatar, Matija

In: The Journal of Physical Chemistry A, 2012, vol. 115, no. 39, p. 10801–10813

The family of the Jahn–Teller (JT) active hydrocarbon rings, CnHn (n = 5–7), was analyzed by the means of multideterminantal density functional theory (DFT) approach. The multimode problem was addressed using the intrinsic distortion path (IDP) method, in which the JT distortion is expressed as a linear combination of all totally symmetric normal...

Université de Fribourg

Computational analysis of tris(1,2-ethanediamine) cobalt(III) complex ion : calculation of the ⁵⁹Co shielding tensor using LF-DFT

Senn, Florian ; Zlatar, Matija ; Gruden-Pavlovic, Maja ; Daul, Claude

In: Monatshefte für Chemie - Chemical Monthly : an International Journal of Chemistry, 2011, vol. 142, no. 6, p. 593-597

The ligand-field density functional theory (LF-DFT) approach is employed for calculations of the ⁵⁹Co nuclear magnetic resonance (NMR) shielding tensor of all four diastereoisomers (λλλ, λλδ, λδδ, and δδδ) of tris(1,2-ethanediamine) cobalt(III) complex ion, [Co(en)₃]³⁺. The obtained values split into two groups according to the point group of the diastereoisomers. 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, no. 5, 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

Electron-driven chemistry of saturated compounds containing oxygen or nitrogen atoms

Ibănescu, Bogdan Cătălin ; Allan, Michael (Dir.)

Thèse de doctorat : Université de Fribourg, 2009.

The broad aim of the present work was to improve our understanding of dissociative electron attachment (DEA) processes mediated by Feshbach resonances. DEA represents an important class of processes leading to electron-driven chemical change. Depending on the nature of the resonance (the transient negative ion) which mediates it, DEA processes can be divided into several types. Out of these, the...

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

A new method to describe the multimode Jahn-Teller effect using density functional theory

Zlatar, Matija ; Schläpfer, Carl-Wilhelm ; Daul, Claude A.

In: Springer Series in Chemical Physics, 2010, vol. 97, p. 131-165

A new method for the analysis of the adiabatic potential energy surfaces of Jahn–Teller (JT) activemolecules is presented. It is based on the analogy between the JT distortion and reaction coordinates. Within the harmonic approximation the JT distortion can be analysed as the linear combination of all totally symmetric normal modes in the low symmetry minimum energy conformation. Contribution...

Université de Fribourg

Intrinsic distortion path in the analysis of the Jahn–Teller effect

Zlatar, Matija ; Gruden-Pavlović, Maja ; Schläpfer, Carl-Wilhelm ; Daul, Claude A

In: Journal of Molecular Structure: THEOCHEM, 2010, vol. 954, p. 86-93

The multideterminental-DFT approach was performed in order to calculate the Jahn–Teller (JT) parameters for the JT active molecules. Within the harmonic approximation the JT distortion can be analysed as a linear combination of all totally symmetric normal modes in any of the low symmetry minimum energy conformation, which allows to calculate the Intrinsic Distortion Path (IDP), exactly from...

Université de Fribourg

Density functional theory for the study of the multimode Jahn-Teller effect

Zlatar, Matija ; Gruden-Pavlović, Maja ; Schläpfer, Carl-Wilhelm ; Daul, Claude A.

In: Chimia, 2010, vol. 64, no. 3, p. 161-164

The Jahn-Teller (JT) theorem states that in a molecule with a degenerate electronic state, a structural distortion must occur that lowers the symmetry, removes the degeneracy and lowers the energy. The multideterminental-DFT method performed to calculate the JT parameters for JT active molecules is described. Within the harmonic approximation the JT distortion can be analyzed as a linear...

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...

Université de Fribourg

Electron scattering in HCl: An improved nonlocal resonance model

Fedor, Juraj ; Winstead, C. ; McKoy, V. ; Čížek, M. ; Houfek, K. ; Kolorenč, P. ; Horáček, J.

In: Physcial Review A, 2010, vol. 31, no. 4, p. 042702

We present an improved nonlocal resonance model for electron-HCl collisions. The short-range part of the model is fitted to ab initio electron-scattering eigenphase sums calculated using the Schwinger multichannel method, while the long-range part is based on the ab initio potential-energy curve of the bound anion HCl-. This model significantly improves the agreement of nonlocal resonance...