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

A dramatic difference between the electron-driven dissociation of alcohols and ethers and its relation to Rydberg states

Ibănescu, Bogdan C. ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2008, vol. 10, p. 5232 - 5237

A difference was observed in the reactivity of alcohols and ethers toward free electrons. Whereas the lowest core-excited state of the negative ion—a ²(n,3s²) Feshbach resonance—of the alcohols readily dissociates by losing a hydrogen atom, ethers show no observable signal from this resonance. This difference in reactivity has a parallel in the anomalous shapes and energies of the...

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

Cleavage of the ether bond by electron impact: differences between linear ethers and tetrahydrofuran

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

In: Physical Chemistry Chemical Physics, 2008, vol. 10, p. 1507-1511

Dissociative electron attachment (DEA) to diethyl ether yielded primarily the C₂H₅O⁻ ion, with a strong Feshbach resonance band at 9.1 eV and a weaker shape resonance band at 3.89 eV. Very similar spectra were obtained for dibutyl ether, with C₄H₉O⁻ bands at 8.0 and 3.6 eV. Some of these primary ions subsequently lost H₂ and yielded weaker signals of the C₂H₃O⁻ and...

Université de Fribourg

Electron-induced chemistry of alcohols

Ibănescu, Bogdan C. ; May, Olivier ; Monney, Angèle ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2007, vol. 9, p. 3163-3173

We studied dissociative electron attachment to a series of compounds with one or two hydroxyl groups. For the monoalcohols we found, apart from the known fragmentations in the 6–12 eV range proceeding via Feshbach resonances, also new weaker processes at lower energies, around 3 eV. They have a steep onset at the dissociation threshold and show a dramatic D/H isotope effect. We assigned...