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Die gewachsenen Anforderungen an die Motorbaureihen 2000 und 4000 der MTU Friedrichshafen verlangen parallel zur Weiterentwicklung des Motors eine kontinuierliche Weiterentwicklung der Motorelektronik. Das Motormanagementsystem ADEC („Advanced Diesel Engine Control“) stellt diesbezuglich einen Quantensprung dar: Anspruche wie weltweit verscharfte Umweltgesetze, Leistungssteigerung, Verringerung von Lebenszykluskosten und Wartungsfreundlichkeit wurden ebenso berucksichtigt wie der querschnittliche Einsatz fur unterschiedliche Anwendungen im gesamten Off-Highway-Markt. Trotz verscharfter Emissionsgesetzgebung kann die MTU mit der ADEC die steigende Leistungsfahigkeit heutiger Grosdieselmotoren darstellen. Aus diesen Moglichkeiten erwachst allerdings auch die Notwendigkeit, sich mit Themen auseinanderzusetzen, die bisher primar im Bereich der EDV angesiedelt waren.

The increased demands on the MTU Friedrichshafen engine Series 2000 and 4000 require not just continuous development of the engine itself but simultaneously also of the engine electronics. The ADEC engine management system (Advanced Diesel Engine Control) represents a quantum leap in this respect: Apart from requirements such as more stringent emission legislation worldwide, increase in power output, reduction of life cycle costs and increase in maintenance-friendliness the possibility of use for different applications across the entire Off-Highway segment was also taken into account. Despite more stringent emission legislation, ADEC allows MTU to increase the performance of current large diesel engines. However, these possibilities also require dealing with subjects that to date were primarily found in the IT sector.

Bimetallic AunXm clusters (X=Cu, Al, Y, In) have been produced by a dual-target dual-laser vaporization source. Following multiphoton absorption the stability patterns resulting from fragmentation are investigated by time-of-flight mass abundance spectrometry. AunCum+ clusters exhibit the same electronic shell effects as Aun+. Different abundance patterns are observed for AunAl1+ compared to AunY1+ or AunIn1+. The patterns are related to the magic numbers of the electronic shell model for clusters. The differences between the bimetallic clusters are interpreted in terms of different cluster geometries dependent on the nature of the dopant atoms.

Free charged and neutral Ag n clusters were produced by a laser vaporization cluster source and deposited onto SiO 2 substrates resulting in cluster films. These films were characterized by atomic force microscopy, X-ray diffraction and resistivity measurements to determine film topography, grain sizes, dimensions of the coherent scattering regions perpendicular to the film plane, and the mean free path length of the conduction electrons. An Ag film grown by molecular beam deposition was investigated using the same characterization techniques. The results show that the deposited clusters keep at least part of their shape upon impact on the substrate, giving rise to growth patterns and film properties distinctly different from those of conventionally grown films.

Small tungsten cluster anions Wn− (n=4–9 and 18–20) are stored in a Penning trap and electronically excited by photoabsorption (Ehν=1.815, 2.33, 3.5, and 4.66 eV). Delayed electron emission is observed on the milliseconds time scale by systematic variation of the storage duration between laser excitation and ion detection. Even if the photon energy exceeds the electron detachment energy, electrons are emitted several milliseconds after laser excitation. The electron emission time constant is determined as a function of the laser pulse energy. An Arrhenius analysis suggests that the observed delayed electron emission is a thermal process in analogy to thermionic emission of bulk materials. As shown by these experiments there is a simple rule for the dominating cooling channel of laser excited clusters: thermionic emission generally occurs as long as the electron binding energy is lower than the dissociation energy.

We report on the production of small and medium size lithium and lithium oxide clusters by a laser vaporization cluster source. The isotopomeric distribution of natural lithium allowed to identify LikO clusters as the most abundant components in the mass spectrum. Photoionization efficiency curves of LikO clusters with photon energies from 3.4 to 4.7 eV were measured for 8 ≤ k ≤ 27. Using linear extrapolation of the increase in photoionization efficiency with photon energy, ionization potentials were extracted. With the chemical bond of the O2- anion to two Li atoms, leaving n = k-2 valence electrons in the (Li2O)Lin clusters, clear shell closure effects are present at n = 8 and n = 20.

We report on the measurement of ionization potentials of lithium monoxide and lithium monocarbide clusters by threshold laser ionization spectroscopy. The clusters are produced by a laser vaporization source, mass selected, and detected by a reflectron time-of-flight mass spectrometer. The values obtained for the ionization potentials of the small clusters are consistent with hypervalent molecular bonding mechanisms. For the larger clusters the evolution of the ionization potentials with size is in agreement with metallic behavior as evidenced by several distinct steps and a pronounced odd-even staggering superposed on a smoothly decreasing trend. The steps in the ionization potentials correspond to the magic numbers predicted by cluster shell models (2, 8, 20, 40,…), provided that n−2, respectively n−4, electrons are delocalized in the clusters LinO and LinC.

We present the development of a sensitive method for the study of atomization processes via the metastable state population and kinetic energy distributions of sputtered atoms, including atoms on high-lying metastable electronic states. The experimental procedure is based on two-colour two-step resonant photoionization. We report on the population distribution of Ar ion sputtered Ni and Co atoms. The measurements show unexpectedly high populations on metastable states with energies above 1.5 eV. The kinetic energy distributions of Ni atoms on such states support the importance of bandstructure effects in the excitation mechanism of atoms after ion beam sputtering.

The competition between electron emission and unimolecular dissociation following the absorption of a single photon is studied for small clusters of various elements. Electron emission results from either direct photoemission, observed as a series of peaks in the spectrum, or thermionic emission, giving rise to a continuous background. Depending on the energetics involved, thermionic emission is in competition with evaporation of atoms. These results are compared to the corresponding events observed for solids, where the dominant decay products are inelastically scattered photoelectrons.

Lithium clusters doped with carbon atoms are studied by threshold photoionization spectroscopy and ionization potentials are deduced for Li n C ( n ⩽70). The evolution of the ionization potentials with size shows distinct steps at n =24 and n =44, suggesting metallic behavior with n −4 free electrons in the larger clusters. Deviations from the metal-like behavior for the size range n

A new dual-target dual-laser vaporization source for the production of binary metallic clusters is presented. Clusters of the type AunXm (X=Al, Fe, Co, Ni) were produced. Excellent control over the mixing process was achieved by varying the delay time between the firing of the two lasers and their energy densities. Having identified these critical parameters, their influence over the production process is shown in detail for the AunAlm system. The production of bimetallic clusters in this source is due to the spatial and temporal overlap of the two laser vaporized materials in the source.

We report on a combined experimental and theoretical investigation of the ionization potentials of small lithium monocarbide clusters. The clusters were produced by a laser vaporization source, and their ionization potentials were measured by threshold photoionization spectroscopy. The structures of the smaller clusters (n≤8), which are governed by hypervalent (hyperlithiated) bonding mechanisms, were calculated by means of density functional theory. Vertical and adiabatic ionization potentials were computed and compared with the experimental data.

Size-selected gold clusters, Open image in new window (n ≤ 21), and tungsten clusters, Open image in new window , and Open image in new window (n = 4 – 8 and 12), stored in a Penning trap have been collisionally activated. Neutral monomer and dimer evaporation are observed in the case of gold. While no fragment products have been observed for tungsten clusters, there is evidence of electron emission from the anions.