Université de Fribourg

Shape and core-excited resonances in thiophene

Loupas, Alexandra ; Regeta, Khrystyna ; Allan, Michael ; Gorfinkiel, Jimena D.

In: The Journal of Physical Chemistry A, 2018, vol. 122, no. 4, p. 1146–1155

We present a comprehensive study of resonance formation in electron collisions with thiophene. Detailed calculations have been performed using the ab initio R-matrix method. Absolute differential cross sections for electron impact excitation up to 18 eV and for two scattering angles, 90 and 135°, have been measured. Agreement between the calculated and measured experimental cross sections is...

Université de Fribourg

Cis- and trans-9,10-di(1H-imidazol-1-yl)-anthracene based coordination polymers of ZnII and CdII: synthesis, crystal structures and luminescence properties

Vasylevskyi, Serhii I. ; Regeta, Khrystyna ; Ruggi, Albert ; Petoud, Stéphane ; Piguet, Claude ; Fromm, Katharina M.

In: Dalton Transactions, 2018, vol. 47, no. 2, p. 596–607

New functional coordination polymers based on the semi-flexible 9,10-di(1H-imidazol- 1-yl)-anthracene ligand (L) with ZnII and CdII, namely {[Zn(μ2-L)2] (ClO4)2·m(MeOH)·n(DCM)}n (1), {[Zn(μ2-L)2](BF4)2·m(MeOH)·n(DCM)}n (2), {[Zn(μ2-L)2(p-Tos)2]·m(DCM)·n(MeOH)}n (3), {[Cd(μ2-L)2(p-Tos)2]·m(DCM)}n (4) {[Cd(μ2-L)2(p-Tos)2]·m(MeOH)·n(Dioxane)}n (5) and {[Zn(μ2-...

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

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

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

Two-dimensional spectra of electron collisions with acrylonitrile and methacrylonitrile reveal nuclear dynamics

Regeta, Khrystyna ; Allan, Michael

In: The Journal of Chemical Physics, 2015, vol. 142, no. 18, p. 184307

Detailed experimental information on the motion of a nuclear packet on a complex (resonant) anion potential surface is obtained by measuring 2-dimensional (2D) electron energy loss spectra. The cross section is plotted as a function of incident electron energy, which determines which resonant anion state is populated, i.e., along which normal coordinate the wave packet is launched, and of the...

Université de Fribourg

Transient anions of cis- and trans-cyclooctene studied by electron-impact spectroscopy

Regeta, Khrystyna ; Nagarka, Amit ; Kilbinger, Andreas F. M. ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2015, vol. 17, no. 6, p. 4696–4700

The effect which deformation of the double bond in trans-cyclooctene (TCO), compared to cis-cyclooctene (CCO), has on its negative ion – and indirectly on the π* virtual orbital – was studied by electron-impact spectroscopy. Differential elastic and vibrational excitation cross sections were measured at a scattering angle of θ = 135°. The vertical attachment energy (VAE) derived from the...

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

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,...