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Université de Fribourg

Partial cross sections for dissociative electron attachment to tetrahydrofuran reveal a dynamics-driven rich fragmentation pattern

Janečková, Radmila ; May, Olivier ; Milosavljević, A.R. ; Fedor, Juraj

In: International Journal of Mass Spectrometry, 2014, vol. 365–366, p. 163–168

We report partial absolute cross sections for dissociative electron attachment (DEA) to tetrahydrofuran C₄H₈O. The high sensitivity of the present setup, quantitative DEA spectrometer with time-of-flight analyzer, led to identification of a number of previously unreported fragments (CH₂⁻, OH⁻, CHO⁻, C₄H₅O⁻, C₃H₃⁻) thus revealing complex dissociation dynamics of the...

Université de Fribourg

Experimental evidence on the mechanism of dissociative electron attachment to formic acid

Janečková, Radmila ; Kubala, Dušan ; May, Olivier ; Fedor, Juraj ; Allan, Michael

In: Physical Review Letters, 2013, vol. 111, no. 21, p. 213201

Two mechanisms for dissociative electron attachment in HCOOH, the formation of HCOO−+H, were proposed in the literature: (i) via a direct electron attachment into a σ∗ resonance, augmented by dipole binding of the incident electron [G. A. Gallup et al., Phys. Rev. A 79, 042701 (2009)], and (ii) with the 1.8 eV π∗ resonance as a doorway state, linked to the products by...

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

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

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

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 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

Low-energy electron attachment to the dichlorodifluoromethane (CCl₂F₂) molecule

Graupner, K. ; Haughey, S. A. ; Field, T. A. ; Mayhew, C. A. ; Hoffmann, T. H. ; May, Olivier ; Fedor, Juraj ; Allan, Michael ; Fabrikant, Ilya I. ; Illenberger, E. ; Braun, M. ; Ruf, M.-W. ; Hotop, Hartmut

In: The Journal of Physical Chemistry A, 2010, vol. 114, no. 3, p. 1474–1484

Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl₂F₂) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl⁻ was measured over the energy range 0.001−1.8 eV at the gas...