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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

Absolute cross sections for dissociative electron attachment to acetylene and diacetylene

May, Olivier ; Fedor, Juraj ; Ibănescu, Bogdan C. ; Allan, Michael

In: Physical Review A, 2008, vol. 77, no. 4, p. 040701

Absolute cross sections for the production of the two astronomy-relevant negative ions H−C≡C⁻ and H−C≡C−C≡C⁻ by dissociative electron attachment to acetylene C₂H₂ and diacetylene C₄H₂ were measured (with a ±25% error bar). Acetylene yielded the C₂H⁻ ion at an electron energy of 2.95 eV with a cross section of 3.6±0.9 pm² and also the C₂⁻ ion at 8.1 eV...

Université de Fribourg

Absolute cross sections for dissociative electron attachment to HCl, HBr, and their deuterated analogs

Fedor, Juraj ; May, Olivier ; Allan, Michael

In: Physical Review A, 2008, vol. 78, p. 032701

We have measured absolute dissociative electron attachment cross sections for HX and DX (X=Cl and Br) using a trochoidal electron spectrometer equipped with a total ion collection collision chamber, operated both in a field-free passive ion collection mode, and an active ion collection mode, with an extracting electric field. Our results for Br⁻ from HBr are in an excellent...

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.

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

Dissociative electron attachment and electronic excitation in Fe(CO)5

Allan, Michael ; Lacko, M. ; Papp, P. ; Matejčík, Š. ; Zlatar, Matija ; Fabrikant, Ilya I. ; Kočišek, J. ; Fedor, Juraj

In: Physical Chemistry Chemical Physics, 2018, vol. 20, no. 17, p. 11692–11701

In a combined experimental and theoretical study we characterize dissociative electron attachment (DEA) to, and electronically excited states of, Fe(CO)5. Both are relevant for electron-induced degradation of Fe(CO)5. The strongest DEA channel is cleavage of one metal–ligand bond that leads to production of Fe(CO)4−. High- resolution spectra of Fe(CO)4− reveal fine structures at the...

Université de Fribourg

Dissociative electron attachment to HBr: A temperature effect

Fedor, Juraj ; Cingel, M. ; Skalný, J. D. ; Scheier, P. ; Märk, T. D. ; Čížek, M. ; Kolorenč, P. ; Horáček, J.

In: Physical Review A, 2007, vol. 75, p. 022703

The effects of rovibrational temperature on dissociative electron attachment to hydrogen bromide has been investigated from the experimental and theoretical point of view. Theoretical calculations based on the nonlocal resonance model predict a strong temperature effect on the Br⁻ fragment ion yield due to population of higher vibrational and rotational states. A crossed beam experimental setup...

Université de Fribourg

Dissociative electron attachment to methylacetylene and dimethylacetylene: Symmetry versus proximity

Janečková, Radmila ; May, Olivier ; Fedor, Juraj

In: Physical Review A - Atomic, Molecular, and Optical Physics, 2012, vol. 86, no. 05, p. 052702

We have measured absolute dissociative electron attachment (DEA) cross sections in methylacetylene (propyne, C₃H₄) and dimethylacetylene (but-2-yne, C₄H₆). The main feature in the low-energy DEA spectrum is a π* shape resonance giving rise to fragments at 3.4 eV in C₃H₄ and 4.0 eV in C₄H₆. The process C₃H₄+e→ C₃H₃ −+H proceeds via abstraction...

Université de Fribourg

Electron attachment properties of c-C₄F₈O in different environments

Chachereau, A. ; Fedor, Juraj ; Janečková, Radmila ; Kočišek, J. ; Rabie, M. ; Franck, C. M.

In: Journal of Physics D: Applied Physics, 2016, vol. 49, no. 37, p. 375201

The electron attachment properties of octafluorotetrahydrofuran (c-C₄F₈O) are investigated using two complementary experimental setups. The attachment and ionization cross sections of c-C₄F₈O are measured using an electron beam experiment. The effective ionization rate coefficient, electron drift velocity and electron diffusion coefficient in c-C₄F₈O diluted to concentrations...