Bastian C. Krüger

Georg-August-Universität Göttingen, Göttingen, Lower Saxony, Germany

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Publications (5)26.42 Total impact

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    ABSTRACT: The loss or gain of vibrational energy in collisions of an NO molecule with the surface of a gold single crystal proceeds by electron transfer. With the advent of new optical pumping and orientation methods, we can now control all molecular degrees of freedom important to this electron-transfer-mediated process, providing the most detailed look yet into the inner workings of an electron-transfer reaction and showing how to control its outcome. We find the probability of electron transfer increases with increasing translational and vibrational energy as well as with proper orientation of the reactant. However, as the vibrational energy increases, translational excitation becomes unimportant and proper orientation becomes less critical. One can understand the interplay of all three control parameters from simple model potentials.
    Angewandte Chemie International Edition 10/2014; · 11.34 Impact Factor
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    ABSTRACT: Stößt ein NO-Molekül mit der Oberfläche eines Gold-Einkristalls, kann das Molekül Schwingungsenergie an die Oberfläche abgeben oder Energie in Form von Schwingungsenergie aufnehmen. Diese Energieübertragung erfolgt über einen Elektronentransferprozess. Durch die Entwicklung neuer Methoden im Bereich des optischen Pumpens und zur Orientierung von Molekülen können jetzt alle wichtigen Freiheitsgrade für diesen Elektronentransferprozess kontrolliert werden. Dadurch erhalten wir tiefen Einblick in die Funktionsweise der Elektronentransferreaktion und demonstrieren, wie diese beeinflusst werden kann. Es zeigt sich, dass die Wahrscheinlichkeit für einen Elektronentransfer mit zunehmender Translations- und Schwingungsenergie sowie mit geeigneter Orientierung ansteigt. Wenn die Schwingungsenergie allerdings sehr hoch ist, wird die Translationsenergie unwichtig, und auch die Orientierung in Bezug auf die Oberfläche verliert an Bedeutung. Das Zusammenspiel aller drei Kontrollparameter kann anhand einfacher Modellpotentiale verstanden werden.
    Angewandte Chemie 10/2014;
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    ABSTRACT: doi: 10.1021/jz401266m
    Journal of Physical Chemistry Letters 07/2013; 4(14):2367-2370. · 6.69 Impact Factor
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    ABSTRACT: Recent studies have suggested that the reaction of stabilised Criegee Intermediates (CIs) with sulfur dioxide (SO(2)), leading to the formation of a carbonyl compound and sulfur trioxide, is a relevant atmospheric source of sulfuric acid. Here, the significance of this pathway has been examined by studying the formation of gas phase products and aerosol during the ozonolysis of β-pinene and 2-butene in the presence of SO(2) in the pressure range of 10 to 1000 mbar. For β-pinene at atmospheric pressure, the addition of SO(2) suppresses the formation of the secondary ozonide and leads to highly increased nopinone yields. A complete consumption of SO(2) is observed at initial SO(2) concentrations below the yield of stabilised CIs. In experiments using 2-butene a significant consumption of SO(2) and additional formation of acetaldehyde are observed at 1 bar. A consistent kinetic simulation of the experimental findings is possible when a fast CI + SO(2) reaction rate in the range of recent direct measurements [Welz et al., Science, 2012, 335, 204] is used. For 2-butene the addition of SO(2) drastically increases the observed aerosol yields at higher pressures. Below 60 mbar the SO(2) oxidation induced particle formation becomes inefficient pointing to the critical role of collisional stabilisation for sulfuric acid controlled nucleation at low pressures.
    Physical Chemistry Chemical Physics 10/2012; · 4.20 Impact Factor
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    ABSTRACT: The ozonolysis of cyclohexene is studied with respect to the pressure dependent formation of stable gas-phase products and secondary organic aerosol (SOA) as well as the influence of the presence of SO(2). In addition the rate coefficient for the initial reaction cyclohexene + O(3) was determined at 295 K. The observed increase in CO and ethene yields at low pressures and the absence of ketene in the product spectrum confirm previously proposed reaction pathways forming these decomposition products. An enhanced ethene formation at pressures below 300 mbar coincides with drastically decreased aerosol yields pointing to a high influence on SOA formation of chemical activation driven dynamics in the vinylhydroperoxide channel. The static reactor experiments at 450 mbar in the presence of SO(2) in the present study showed a similar sensitivity of additional particle formation to H(2)SO(4) number densities as found in near-atmospheric flow reactor experiments [Sipiläet al., Science, 2010, 327, 1243], a surprising result with regard to the very different experimental approaches. At low pressures (around 40 mbar) no significant new particle formation is observed even at high H(2)SO(4) concentrations. These findings indicate that the collisional stabilisation of initial clusters is an important aspect for SOA formation processes involving sulfuric acid and organic compounds. The results may have implications for geo-engineering strategies based on stratospheric sulfur injection, but caution is mandatory when room temperature laboratory results are extrapolated to stratospheric conditions.
    Physical Chemistry Chemical Physics 07/2012; 14(33):11695-705. · 4.20 Impact Factor