On line engine oil consumption monitoring via the gaseous total sulfur signal SO2 in the raw exhaust of the engine utilizing the sensitive ion molecule reaction mass spectrometry

The dynamic monitoring of oil consumption in IC engines is approached with various techniques ranging from radioactive counting to detection of halogenated tracer compounds or polyaromatic hydrocarbon tracers, to monitoring unburned hydrocarbons as residues from engine oil. This article discusses the method of gaseous SO2 measurement in raw exhaust it's benefits and limitations of today’s status. Modern engines consume about 2 to 5 g/h of engine oil under low and medium load but consumption may go up to 130 g/h in negative load conditions. Particulate filters must be desulfated every 5000 km even when sulfur free fuel is in use. For the oil measurement in the raw exhaust all possible Sulfur compounds are converted to SO2 in a hot oxidizing atmosphere. Additional pure oxygen in the form of ozone is added to the oxidizer for very low lambda engine conditions and the conversion of sulfur on particulates into SO2. A sensitive mass spectrometer operating in an ion molecule ionization mode measures gaseous SO2 from concentrations of 0.02 ppm to 50 ppm in measurement cycles from 2 Hz to 0.2 Hz depending on if long term measurement or dynamic operation is chosen. Technical description of pressure reduction, gas transfer, oxidation efficiencies and lower detection levels of the instrumentation are given as well as data on a complete engine map and data on reproducibility of the SO2 method are presented

High-resolution mass spectrometric study of pure helium droplets, and droplets doped with krypton

Mass spectra of doped and undoped helium droplets are presented. The high resolution of the time-of-flight spectrometer (m/Delta m a parts per thousand... 5000) makes it possible to fully resolve small helium cluster ions from impurities and to unambiguously identify abundance anomalies in the size distribution of He (n) (+). The yield of He(4) (+) shows the well-known enhancement relative to other small cluster ions when the expansion changes from sub- to supercritical, provided the electron energy exceeds a value of 40 +/- A 1 eV, the threshold for formation of electronically excited ions. Upon doping with krypton, pure Kr (n) (+) cluster ions containing up to 41 Kr atoms are observed. The spectra exhibit abundance anomalies at 13, 16, 19, 22 & 23, 26 and 29, in agreement with spectra obtained by ionization of bare krypton clusters that are formed in neat supersonic beams. Mixed clusters He (m) Kr(+) indicate closure of a solvation shell at m = 12

Electron impact on N<inf>2</inf>/CH<inf>4</inf> mixtures in He droplets - Probing chemistry in Titan's atmosphere

In this work a low-energy electron beam is used to irradiate mixtures of nitrogen and methane in helium droplets. The formation of heterogeneous ionic species due to ionization is observed and the corresponding chemical structures and binding energies are calculated. Formation of a CN bond in CH 3N2+ is shown computationally, which indicates the possibility of synthesis of true chemical bonds. The formation of CN bonds in organic molecules is of relevance for understanding atmospheric chemistry, for example in Titan's atmosphere

Methane Adsorption on Graphitic Nanostructures: Every Molecule Counts

[Image: see text] Bundles of single-walled nanotubes are promising candidates for storage of hydrogen, methane, and other hydrogen-rich molecules, but experiments are hindered by nonuniformity of the tubes. We overcome the problem by investigating methane adsorption on aggregates of fullerenes containing up to six C(60); the systems feature adsorption sites similar to those of nanotube bundles. Four different types of adsorption sites are distinguished, namely, registered sites above the carbon hexagons and pentagons, groove sites between adjacent fullerenes, dimple sites between three adjacent fullerenes, and exterior sites. The nature and adsorption energies of the sites in C(60) aggregates are determined by density functional theory and molecular dynamics (MD) simulations. Excellent agreement between experiment and theory is obtained for the adsorption capacity in these sites

Submersion of potassium clusters in helium nanodroplets

Small alkali clusters do not submerge in liquid helium nanodroplets but instead survive predominantly in high spin states that reside on the surface of the nanodroplet. However, a recent theoretical prediction by Stark and Kresin [Phys. Rev. B 81, 085401 (2010)], based on a classical description of the energetics of bubble formation for a fully submerged alkali cluster, suggests that the alkali clusters can submerge on energetic grounds when they exceed a critical size. Following recent work on sodium clusters, where ion yield data from electron impact mass spectrometry was used to obtain the first experimental evidence for alkali cluster submersion, we report here on similar experiments for potassium clusters. Evidence is presented for full cluster submersion at n>80 for Kn clusters, which is in good agreement with the recent theoretical prediction. In an additional observation, we report “magic number” sizes for both Kn+ and Kn2+ ions derived from helium droplets, which are found to be consistent with the jellium model

On the Size and Structure of Helium Snowballs Formed around Charged Atoms and Clusters of Noble Gases

[Image: see text] Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. He(n)Ng(x)(+) ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He(20)(84)Kr(2)(+) and the isobaric, nonmagic He(41)(84)Kr(+). Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for He(n)Ar(+), which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for He(n)Na(+) [J. Phys. Chem. A2011, 115, 730021568337] that reveal three shells of icosahedral symmetry. He(n)Ar(x)(+) (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of He(n)Kr(x)(+) suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr(+) to Kr(3)(+). Previously reported strong anomalies at He(12)Kr(2)(+) and He(12)Kr(3)(+) [ J. H. Kim; et al. J. Chem. Phys.2006, 124, 21430116774401] are attributed to a contamination. Only minor local anomalies appear in the distributions of He(n)Xe(x)(+) (x ≤ 3). The distributions of He(n)Kr(+) and He(n)Xe(+) show strikingly similar, broad features that are absent from the distribution of He(n)Ar(+); differences are tentatively ascribed to the very different fragmentation dynamics of these ions