72 research outputs found
Control of chemical reactions by electron radiation
No full textInteraction between low-energy electrons and molecules can lead to dissociative electron attachment (DEA) or dissociative ionization (DI). In condensed matter, the resulting reactive fragments can attack adjacent molecules to yield larger products. In this thesis, reactions initiated by DEA to acetonitrile in condensed phase have been compared to the known gas phase fragmentation channels. Also, gas phase DEA experiments have been performed on chlorosilanes to study the effect of a variation of the organic ligands on the energy of their molecular orbitals and reactivity in DEA processes. Furthermore, hydroamination reactions induced by DI for different alkenes and amines have been investigated. A similar reaction of ammonia and carbon monoxide was shown to produce formamide (HCONH2), which is the smallest molecule to contain a peptide bond and thus represents an important building block of biologically relevant substances
Low energy ELEctron driven chemistry for the advantage of emerging NAno-fabrication methods (ELENA); a Marie Skłodowska-Curie Innovative Training Network
No full textLaser desorption electron attachment time-of-flight mass spectrometry: a new approach to detection of involatile compounds
No full textAbstractWe report initial results of a new method for obtaining mass spectra of involatile compounds: laser desorption electron attachment time-of-flight mass spectrometry. With this approach, laser desorbed neutral molecules are entrained in a molecular beam and subsequently ionized by low energy electron attachment. Mass analysis is carried out by a linear time-of-flight. We present a description of the apparatus and a number of examples of our early results on: van der Waals condensates of SF6, Fullerenes, derivatized Fullerenes, perfluorinated polyethers, polyphenylethers, and 5-bromouracil
HF Formation through Dissociative Electron Attachment—A Combined Experimental and Theoretical Study on Pentafluorothiophenol and 2-Fluorothiophenol
No full textIn chemoradiation therapy, dissociative electron attachment (DEA) may play an important role with respect to the efficiency of the radiosensitizers used. The rational tailoring of such radiosensitizers to be more susceptive to DEA may thus offer a path to increase their efficiency. Potentially, this may be achieved by tailoring rearrangement reactions into the DEA process such that these may proceed at low incident electron energies, where DEA is most effective. Favorably altering the orbital structure of the respective molecules through substitution is another path that may be taken to promote dissociation up on electron capture. Here we present a combined experimental and theoretical study on DEA in relation to pentafluorothiophenol (PFTP) and 2-fluorothiophenol (2-FTP). We investigate the thermochemistry and dynamics of neutral HF formation through DEA as means to lower the threshold for dissociation up on electron capture to these compounds, and we explore the influence of perfluorination on their orbital structure. Fragment ion yield curves are presented, and the thermochemical thresholds for the respective DEA processes are computed as well as the minimum energy paths for HF formation up on electron capture and the underlying orbital structure of the respective molecular anions. We show that perfluorination of the aromatic ring in these compounds plays an important role in enabling HF formation by further lowering the threshold for this process and through favorable influence on the orbital structure, such that DEA is promoted. We argue that this approach may offer a path for tailoring new and efficient radiosensitizers
Riddarar götunnar : frá götumenningu í hönnun og listir
No full textGuðmundur Oddur „Goddur“ Magnússon tók fram í grein Morgunblaðsins árið 2008 að mikið væri um að fólk úr ákveðnum menningarkima sækti í nám við Listaháskóla Íslands. Í ritgerðinni er leitast við að skoða tengingu frá annarsvegar tvemur menningarkimum og hins vegar list sköpunnar og hönnunar.
Um er að ræða menningarkima er tengjast brettaiðkendum og veggjalist en ákveðin tengsl eru þar á milli en í báðum tilfellum er um að ræða menningu sem að kallast getur götumenning. Skoðuð eru dæmi um grafíska hönnuði og listamenn með þennan bakgrunn og skoðað er samhengi þeirra á milli og litið á það hugarfar sem að einkennir fólk úr þessum hópum en oftar en ekki má greina samhengi á milli hugarfars og útkomu í listsköpun þeirra og einnig er hægt að líkja saman einhvern hátt þeim listamönnum sem skoðaðir eru.
Farið er ofan í menningarkimana og skoðað hvort eitthvað sé þar sérstakt sem að ýtir fólki út í skapandi greinar frekar en annað
Bridging the Cluster-to-Bulk Divide: Electron Attachment Time-of-Flight Mass Spectrometry Reveals Geometrical Shell Closings in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi>SF</mml:mi></mml:mrow><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi /></mml:mrow><mml:mrow><mml:mi mathvariant="italic">n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Clusters<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mi mathvariant="italic">n</mml:mi><mml:mspace /><mml:mo>=</mml:mo><mml:mspace /><mml:mn>2</mml:mn><mml:mn /><mml:mi /><mml:mo>–</mml:mo><mml:mi /><mml:mn>550</mml:mn><mml:mo>)</mml:mo></mml:math>
No full textPromoting Reaction Channels in Dissociative Electron Attachment to Improve the Cross-Linking Efficiency of SAMs for the Production of Carbon Nano-Membranes
No full textCipriani M, Terfort A, Koch S, Gölzhäuser A, Ingólfsson O. Promoting Reaction Channels in Dissociative Electron Attachment to Improve the Cross-Linking Efficiency of SAMs for the Production of Carbon Nano-Membranes. In: Cassidy D, Brunger MJ, Petrović ZL, et al., eds. POSMOL 2019 BOOK OF ABSTRACTS. 2019: 131
Proton Shuttling and Reaction Paths in Dissociative Electron Attachment to o- and p-Tetrafluorohydroquinone, an Experimental and Theoretical Study
No full textHere we present a combined experimental and theoretical study on the fragmentation of o- and p-tetrafluorohydroquinone upon low energy electron attachment. Despite an identical ring-skeleton and identical functional groups in these constitutional isomers, they show distinctly different fragmentation patterns, a phenomenon that cannot be explained by distinct resonances or different thermochemistry. Using high-level quantum chemical calculations with the computationally affordable domain localized pair natural orbital approach, DLPNO–CCSD(T), we are able to provide a complete and accurate description of the respective reaction dynamics, revealing proton shuttling and transition states for competing channels as the explanation for the different behavior of these isomers. The results represent a “schoolbook example” of how the combination of experiment and modern high-level theory may today provide a thorough understanding of complex reaction dynamics by computationally affordable means.(This work was supported by the Icelandic Center of Research (RANNIS) Grant No. 13049305
and 141218051 and the University of Iceland Research Fund.Peer Reviewe
- …
