Affiner les résultats

Type de document

Institution

Collection spécifique

Langue

  • Anglais (24) désactiver le filtre
Université de Fribourg

Growth of ice nanoparticles via uptake of individual molecules: pickup cross sections

Fedor, Juraj ; Lengyel, Jozef ; Kočišek, J. ; Poterya, V. ; Pysanenko, A. ; Svrčková, P. ; Fárník, M.

In: Journal of Physics: Conference Series, 2014, vol. 488, no. 10, p. 102016

We present cross sections for pickup of several atmospherically relevant molecules on ice nanoparticles with the 0.5-3 nm diameter range. The experimental values are supported by molecular dynamics simulations and analytical calculations based on long-range cluster-molecule potentials. The cross sections are all considerably larger than the geometrical cross section of nanoparticle and vary...

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...

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

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

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

Long-lived transient anion of c-C₄F₈O

Kočišek, J. ; Janečková, Radmila ; Fedor, Juraj

In: The Journal of Chemical Physics, 2018, vol. 148, no. 7, p. 074303

We report partial cross sections for electron attachment to c-C4F8O, a gas with promising technological applications in free-electron-rich environments. The dissociative electron attachment leads to a number of anionic fragments resulting from complex bond-breaking and bond-forming processes. However, the anion with the highest abundance is the non-dissociated (transient) parent anion which...

Université de Fribourg

The electronic structure of TEMPO, its cation and anion

Kubala, D. ; Regeta, K. ; Janečková, R. ; Fedor, Juraj ; Grimme, S. ; Hansen, A. ; Nesvadba, P. ; Allan, Michael

In: Molecular Physics, 2013, p. -

The electronic structure of TEMPO (2,2,6,6-Tetramethylpiperidine-N-oxyl) and its cation and anion were studied experimentally using the electron spectroscopy techniques, dissociative electron attachment (DEA) spectroscopy, electron energy-loss spectroscopy, measurement of elastic and vibrational excitation (VE) cross sections and HeI photoelectron spectroscopy. The experiments were supplemented...

Université de Fribourg

Uptake of atmospheric molecules by ice nanoparticles: Pickup cross sections

Lengyel, J. ; Kočišek, J. ; Poterya, V. ; Pysanenko, A. ; Svrčková, P. ; Fárník, M. ; Zaouris, D. K. ; Fedor, Juraj

In: Journal of Chemical Physics, 2012, vol. 137, p. 034304

Uptake of several atmospheric molecules on free ice nanoparticles was investigated. Typical examples were chosen: water, methane, NOx species (NO, NO₂), hydrogen halides (HCl, HBr), and volatile organic compounds (CH₃OH, CH₃CH₂OH). The cross sections for pickup of these molecules on ice nanoparticles (H₂O)N with the mean size of ***Missing image...

Université de Fribourg

Oxidation of sterols: energetics of C–H and O–H bond cleavage

Lengyel, Jozef ; Rimarčík, Ján ; Vagánek, Adam ; Fedor, Juraj ; Lukeš, Vladimír ; Klein, Erik

In: Food Chemistry, 2012, vol. 133, no. 4, p. 1435–1440

Phytosterols, as components of human diet, received much attention because of their cholesterol-lowering and antioxidant properties. We have theoretically studied sterols oxidation in terms of O–H and C–H bond dissociation enthalpies (BDE). In 17 Δ⁵- and Δ⁷-sterols, BDEs were obtained for reported sites of oxidation attack. Obtained results indicate that Δ⁷-sterols are more...