Search

The effect of the process gas during laser powder bed fusion (L-PBF) was investigated using high-speed shadowgraphy while melting Ti-6Al-4V powder under high purity argon, helium, and a mixture of both, on a laboratory-scale machine. These recordings reveal that the generation of incandescent spatters can be reduced by at least 60% using pure helium and by ∼30% using addition of helium to argon in comparison to the use of traditional argon. The quantity of colder spatters appeared unaffected by the change of process gas. Different configurations of gas flow versus laser scanning direction were investigated and revealed that fumes and spatters are less accumulated at the laser spot with helium addition. Furthermore, the use of the argon–helium mixture proved to be as efficient as pure argon in the dragging and extraction of the fumes. Shadowgraphs revealed the more rapid expansion of fumes in helium-rich atmospheres, limiting the accumulation of scattering objects close to the laser spot and thus melt pool instability. These results were correlated to process snapshots on an industrial-scale system, confirming the reduction of hot spatter generation. Finally, the findings put in evidence the more rapid cooling of spatters with helium addition to the process gas – a promising aspect to limit powder bed degradation during L-PBF. In addition, the use of mixtures of helium and argon would be economically interesting compared to pure helium, typically more expensive than the traditionally used argon.

Der Fachartikel stellt ein Modell zur Berechnung von Kosten- und Leistungskennwerten für Anlagen für das Laserstrahlschmelzen vor. Die Besonderheiten des Modells liegen dabei in der realitätsnahen Berücksichtigung anwendungsspezifischer Bauteilgeometrien sowie Prozessführungsstrategien von Anlagentechnik und Betriebsbedingungen. Mit Beispielen wird der Einfluss dieser Eingangsgrößen aufgezeigt und die Bedeutung einer möglichst genauen Modellierung herausgestellt. In this paper, a model for the calculation of cost and performance characteristics for laser beam melting systems is presented. The specific features of the model are the realistic consideration of application-specific component geometries, processing strategies, machines and operating conditions. The influence of these input variables is demonstrated by means of examples.

We report the synthesis of a novel isotope engineered $^{13}{\rm C}$--$^{12}{\rm C}$ heteronuclear nanostructure: single-wall carbon nanotubes made of $^{13}{\rm C}$ enriched clusters which are embedded in natural carbon regions. The material is synthesized with a high temperature annealing from $^{13}{\rm C}$ enriched benzene and natural ${\rm C}_{60}$, which are co-encapsulated inside host SWCNTs in an alternating fashion. The Raman 2D line indicates that the $^{13}{\rm C}$ isotopes are not distributed uniformly in the inner tubes. A semi-empirical method based modeling of the Raman modes under $^{13}{\rm C}$ isotope enrichment shows that experimental data is compatible with the presence of $^{13}{\rm C}$ rich clusters which are embedded in a natural carbon containing matrix. This material may find applications in quantum information processing and storage using nuclear spins as qubits., Comment: 8 pages, 4 figures

Volcanic CO

Laser powder bed fusion (l-PBF) has drawn increasing attention as an additive manufacturing technique for industrial production over the last years. However, the existing machine technology constitutes certain limitations in terms of the process itself as well as scalability of melting rate and build envelope. In this paper, new approaches for l-PBF with regard to exposure- and machine concepts as well as beam sources and optical systems are presented.

Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control has been achieved on systems of increasing complexity, however, this control is still sub-optimal. Optimal control theory is the ideal candidate to bridge the gap between early stage and optimal experimental protocols, particularly since it was extended to encompass many-body quantum dynamics. Here, we experimentally demonstrate optimal control applied to two dynamical processes subject to interactions: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We show theoretically that these transformations can be made fast and robust with respect to perturbations, including temperature and atom number fluctuations, resulting in a good agreement between theoretical predictions and experimental results., Comment: 12 pages, 5 figures

Purpose: The determination of attenuation compared to lead for lead-free and lead-reduced protective clothing depends strongly on the different methods of measurement. The standards EN 61331-1 (2002), DIN 6857-1 und IEC 61331-1 (2014) are now available for the testing of protective clothing. These standards define methods in the narrow beam and in the inverse broad beam geometry with partially different radiation qualities. In the narrow beam the scattered radiation and fluorescence are not considered due to the arrangement. Therefore, the protective effect of lead-free materials will be incorrectly estimated compared to lead material. The influence of the different methods of measurement on the lead equivalent and the required mass of radiation protection clothing was examined. Materials and Methods: The lead equivalents for material samples for commercially available protective clothing were determined. These samples were made of lead and lead-reduced and lead-free materials. For determination of the attenuation equivalents, certified lead foils with high purity and a precise thickness of 0.05 to 1.25 mm were used. Results: The measurements indicate that the lead equivalent depends on the method of measurement and the radiation quality. For X-ray tube voltages below 110 kV, lead-free or lead-reduced materials show a higher lead equivalent compared to lead material in some cases. Significant mass reductions of more than 10 % compared to lead material are only achievable with a limited range of use up to 100 kV. Conclusion: The implementation of an internationally accepted measuring standard for radiation protection clothing is reasonable and necessary. If standard IEC 61331-1 (2014) can fill this role is unknown. Key points • The attenuation factor and the lead equivalent depend strongly on the method of measurement. • The used X-ray spectra are only partially comparable with the spectra of scattered radiation. • Mass reductions for protective clothing are only achievable with a limited range of use. Citation Format: • Schopf T, Pichler T. Radiation Protection Clothing in X-Ray Diagnostics – Influence of the Different Methods of Measurement on the Lead Equivalent and the Required Mass. Fortschr Rontgenstr 2016; 188: 768 – 775

Purpose Standard DIN EN 61 331-1 for attenuation measurements in the narrow and broad beam as well as DIN 6857-1 for the determination of shielding properties in the inverse broad-beam geometry are available for testing the attenuation of protection clothing. The attenuation measurements in the narrow beam don't consider scattered radiation and fluorescence due to the arrangement. This leads to the fact that the protective effect of lead-free materials will be misestimated when compared to lead. Therefore, the differences in attenuation equivalents, determined by both test methods for topical radiation protection aprons, were examined. Materials and methods The attenuations in inverse broad-beam geometry according to DIN 6857-1 and in the narrow beam according to DIN EN 61 331-1 were measured using commercially available aprons. They were made of lead, lead-reduced and lead-free materials. For determination of the attenuation equivalents, certificated lead-foils with high purity and a precise thickness of 0.1 to 1.25 mm were used. Results The measurements in the narrow beam according to DIN EN 61 331-1 showed that nearly all aprons reach the required lead equivalent at mid-range tube voltages of 100 kV. At higher and lower tube voltages, the requirements of DIN EN 61 331-3 were largely not met. In contrast, the testing of the same aprons in inverse broad-beam geometry according to DIN 6857-1 showed that only a few aprons meet the requirements for being classified in the nominal protection class. Conclusion The measurements suggest that testing method DIN 6857-1 has yet to prevail and that manufacturers are just beginning to develop the appropriate protective materials.

Ein standardisiertes Vorgehen bei medizinischen Untersuchungen fur Personen, die fur langere Zeit ins Ausland gehen, um dort berufliche oder private Aufgaben wahrzunehmen, ist derzeit im deutschsprachigen Raum nicht ausreichend verankert. Das als Autoren zeichnende Expertengremium versucht, mit Hilfe eines modulartig aufgebauten Untersuchungsprogramms ein moglichst flexibles System fur die per Definition festgelegte "Entsendungseignungsuntersuchung" festzulegen. Dabei werden neben den medizinischen Grundlagen auch okonomische und rechtliche Aspekte fur eine derartige Untersuchung unter Bedachtnahme auf die unterschiedlichen Voraussetzungen der Lander Deutschland, Osterreich, Schweiz ausgearbeitet. Erganzt wird die Ausarbeitung des Untersuchungsprogramms durch Vorschlage zu allgemein gultigen Begriffsdefinitionen rund um Auslandsentsendungen, Definition des Kollektivs der zu Untersuchenden, der Untersucher, der Standardisierung der Aussage des Untersuchungsergebnisses und der reisemedizinischen Aspekte.

We report on the doping dependence of the electronic structure of the valence band of mats of C 60 -filled single wall carbon nanotubes (C 60 peapods) studied by high resolution photoemission spectroscopy. In the pristine state, the bundles consist of approximately one third metallic tubes which are Tomonaga-Luttinger liquids (TLL) and thus show a power law scaling of the density of states near the Fermi level. The power law scaling factor of the pristine peapods is hardly increased compared to that of single-walled carbon nanotubes (SWCNT). Upon doping we find a complex doping behavior and charge distribution between the electronic states of the SWCNT and the encaged C 60 chains. Close to the Fermi level this has consequences on the doping induced crossover from a TLL to a conventional Fermi liquid which is found at a higher charge transfer as compared to intercalated SWCNT bundles.

A photoemission study of potassium intercalated trimetal-nitride fullerene Dy 3 N@C 80 is reported. A continuous electron doping to the carbon cage with increasing potassium intercalation levels is observed as shape changes in the carbon-sensitive ultra-violet photoemission spectrum. X-ray photoemission shows that the valence electronic state of the trivalent Dy ions is not affected by the additional charge in the fullerene cage.

We show that gauge invariant quantum link models, Abelian and non-Abelian, can be exactly described in terms of tensor networks states. Quantum link models represent an ideal bridge between high-energy to cold atom physics, as they can be used in cold-atoms in optical lattices to study lattice gauge theories. In this framework, we characterize the phase diagram of a (1+1)-d quantum link version of the Schwinger model in an external classical background electric field: the quantum phase transition from a charge and parity ordered phase with non-zero electric flux to a disordered one with a net zero electric flux configuration is described by the Ising universality class., Comment: 9 pages, 9 figures. Published version

We compare three different methods for determining an average ‘effective‧ UV albedo. These methods are applied to spectral irradiance data from a measurement campaign held in the German Alps during the spring of 1999. The first method is based on the comparison of measurements of absolute levels of UV irradiance with model calculations. The second method takes advantage of changes in the spectral slope of spectral UV irradiance, which is a function of the surface albedo. In the third method, the surrounding area is partitioned into snow-covered and snow-free regions, and the effective albedo estimated by applying a higher or lower reflectivity to each facet before integrating over the surroundings. We present the differences and the correlations between the various methods as well as the results for the different locations.

We report on the evaluation of the distribution of diameters for nanotube samples with a wide variation of mean diameters. Such results were obtained from a detailed analysis of the radial breathing mode Raman response and compared to results obtained from an evaluation of optical spectra and X-ray diffraction pattern. The evaluation of the Raman data needs a well refined analysis as the experimental analysis exhibits a rather complicated and oscillating relation between response and exciting laser. Both, an exact calculation where the density of states was considered explicitly and an approximate calculation were applied. Both models used for the analysis are able to explain several unexpected results from the experiment such as the oscillating behavior of the spectral moments, unusual discontinuities in the first moments of the Raman response for excitation in the IR, a fine structure for the response in optics and Raman, and an up shift of the RBM frequency as compared to qualified ab initio calculations. In detail the first moment and the variance of the spectra were used for the evaluation of the diameter distribution. To obtain good results between experimental and theoretical oscillation pattern the transition energy between the first two van Hove singularities had to be scaled up which is considered as a result from coulomb interaction of the electrons in the tubular material. On the other hand the analysis does not only allow to determine the mean value and the width of the diameter distribution but yields also a value for the average bundle diameters or, alternatively, the strength of the tube-tube interaction. The model used for the analysis of the Raman data is also appropriate to analyze the optical response, at least for the spectral range from 0.5 eV to 3.5 eV. The fine structure in the response for the transitions between the three lowest van Hove singularities is well reproduced and the mean tube diameters and their distribution is obtained in very good agreement with the results from the Raman analysis. From the X-ray analysis the same mean values and comparable distributions for the tube diameters were received whereas the bundle diameters could not be retained with high precision in this case.

Seven spectroradiorneters measured simultaneous surface UV irradiances at six different sites in the vicinity of Garmisch-Partenkirchen, Germany, during spring 1999. The measured clear-sky irradiance variability between the sites was analyzed with respect to altitude, aerosol optical depth, solar zenith angle, effective albedo, and tropospheric ozone. For conditions of low aerosol loading the increase of irradiance per 1000 m altitude difference was 9% at 400 nm. 20% at 320 nm, and 30% at 300 nm in this season. Effective albedo differences of 0.15, 0.29, and 0.65 were found between the snow-covered stations and the snow-free ground station with the higher effective albedo values determined at the two mountain stations. Clean continental aerosols with a single-scatter albedo of 0.95 were observed during this campaign. The measurements and the observed variations between the sites should enable more accurate modeling studies to be performed for an Alpine environment.

Raman spectra are presented for the single bonded dimeric fullerene (C 60 - ) 2 and compared to optical spectra and Raman spectra of the isostructural and isoelectronic heterofullerene (C59N)2. The spectra of both materials exhibit strong correlations with respect to splitting, line position, and line intensity. This holds for non resonant excitation with blue and green lasers as well as for the strong resonances observed with red lasers. The latter observation is consistent with a downshift for the electronic transition energies as compared to C60. The absorption edge of thin films of (C59N)2 was found at 1.4 eV. The three intercage modes were observed at 82, 103, and 111, and at 88, 98, and 106 cm-1 for (C59N)2 and (C 60 - ) 2 , respectively. A surprising difference was found for the position of the pentagonal pinch modes in the two materials as they were observed at 1461 and at 1451 cm-1, for (C59N)2 and (C 60 - ) 2 , respectively. This is interpreted as a consequence of some characteristic differences in the electronic structure of the two compounds.

We address the question as to whether the topology of the normal-state Fermi surface of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$---as seen in angle-resolved photoemission---depends on the photon energy used to measure it. High-resolution photoemission spectra and Fermi-surface maps from pristine and Pb-doped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ are presented, recorded using both polarized and unpolarized radiation of differing energies. The data show clearly that no main band crosses the Fermi surface along the $\ensuremath{\Gamma}\overline{M}Z$ direction in reciprocal space, even for a photon energy of 32 eV, thus ruling out the existence of a \ensuremath{\Gamma}-centered, electronlike Fermi surface in this archetypal high-${T}_{C}$ superconductor. The true topology of the normal-state Fermi surface remains that of holelike barrels centered at the $X,Y$ points of the Brillouin zone.

We present IR reflectivity measurements on in situ doped C 60 thin films and single crystals in the MIR spectral range. By iterative doping and annealing single phase material for the main stoichiometric phases was obtained. These phases extended over the whole material in the case of the thin films and formed layers up to 4 μm in the case of the single crystals. In the spectral range of the four IR active F 1u modes frequency shift versus charge relations were analysed and at least for two modes a charged phonon behavior was found. Particular attention is paid to the modes of the phase Rb 1 C 60 as a function of temperature and of sample orientation. The fcc → orthorhombic phase transition was revealed by a splitting of the F 1u modes into three lines independent of orientation within a temperature range of 2 degrees at 404 415 K for a cooling/heating cycle, respectively. The reflectivity spectra remained unchanged after exposing the orthorhombic Rb 1 C 60 to air and changed only weakly after heating the crystal beyond the phase transition up to 450 K. The conductivity of both phases shows a weakly activated temperature dependence.

In situ IR reflectivity was used to study the doping of thin ${\mathrm{C}}_{60}$ films with K and Rb by a load and equilibrate procedure. Nearly pure phases of ${\mathit{A}}_{\mathit{x}}$${\mathrm{C}}_{60}$ for x=1, 3, 4, and 6 were obtained in this way and the IR spectra were characterized. A quantitative analysis of the reflectivity spectra using a multilayer response function revealed the line positions, linewidths and the oscillator strengths for the ${\mathit{F}}_{1\mathit{u}}$ modes. The second-lowest mode and the highest mode showed good agreement with the charged phonon model with respect to line shift and absorption intensity and were thus assigned as charged phonon modes. The coupling constants for these modes to the virtual ${\mathit{t}}_{1\mathit{u}}$\ensuremath{\rightarrow}${\mathit{t}}_{1\mathit{g}}$ transition were found to be of the order 0.01. This value is smaller but not negligible compared to the coupling of the gerade modes with ${\mathit{A}}_{\mathit{g}}$ and ${\mathit{H}}_{\mathit{g}}$ symmetry. Thus, the coupling from the virtual ${\mathit{t}}_{1\mathit{u}}$\ensuremath{\rightarrow}${\mathit{t}}_{1\mathit{g}}$ transition may contribute as well to the pairing process in the superconducting phase.

We represent results of IR reflectivity and transmission measurements in the spectral range from 50 to 5000 cm−1 for crystallographic {111} and {100} planes of C60 single crystals between 80 K and 460 K. The spectra turned out to be highly anisotropic due to differences in geometric resonances. The geometries used allowed detailed simultaneous investigation of the four infrared activeF 1u fundamental modes together with some weak silent modes and the whole set of second- and third-order combination modes from an analysis of the reflection-transmission response. Photopolymerization is observed on the surface of the crystals after illumination in argon atmosphere. The orientational phase transition at 260 K is accompanied by a dramatic jump in the line widths within a fraction of a degree. This result is explained by a broadening mechanism due to collisions with librons and paralibrons for the low temperature phase and for the high temperature phase, respectively.

The hydrothermally influenced sediments of Tutum Bay, Ambitle Island, Papua New Guinea, are ideal for investigating the chemolithotrophic activities of micro-organisms involved in arsenic cycling because hydrothermal vents there expel fluids with arsenite (As(III)) concentrations as high as 950 μg L(-1) . These hot (99 °C), slightly acidic (pH ~6), chemically reduced, shallow-sea vent fluids mix with colder, oxidized seawater to create steep gradients in temperature, pH, and concentrations of As, N, Fe, and S redox species. Near the vents, iron oxyhydroxides precipitate with up to 6.2 wt% arsenate (As(V)). Here, chemical analyses of sediment porewaters from 10 sites along a 300-m transect were combined with standard Gibbs energies to evaluate the energy yields (-ΔG(r)) from 19 potential chemolithotrophic metabolisms, including As(V) reduction, As(III) oxidation, Fe(III) reduction, and Fe(II) oxidation reactions. The 19 reactions yielded 2-94 kJ mol(-1) e(-) , with aerobic oxidation of sulphide and arsenite the two most exergonic reactions. Although anaerobic As(V) reduction and Fe(III) reduction were among the least exergonic reactions investigated, they are still potential net metabolisms. Gibbs energies of the arsenic redox reactions generally correlate linearly with pH, increasing with increasing pH for As(III) oxidation and decreasing with increasing pH for As(V) reduction. The calculated exergonic energy yields suggest that micro-organisms could exploit diverse energy sources in Tutum Bay, and examples of micro-organisms known to use these chemolithotrophic metabolic strategies are discussed. Energy modeling of redox reactions can help target sampling sites for future microbial collection and cultivation studies.

Standard DIN EN 61 331-1 for attenuation measurements in the narrow and broad beam as well as DIN 6857-1 for the determination of shielding properties in the inverse broad-beam geometry are available for testing the attenuation of protection clothing. The attenuation measurements in the narrow beam don't consider scattered radiation and fluorescence due to the arrangement. This leads to the fact that the protective effect of lead-free materials will be misestimated when compared to lead. Therefore, the differences in attenuation equivalents, determined by both test methods for topical radiation protection aprons, were examined.The attenuations in inverse broad-beam geometry according to DIN 6857-1 and in the narrow beam according to DIN EN 61 331-1 were measured using commercially available aprons. They were made of lead, lead-reduced and lead-free materials. For determination of the attenuation equivalents, certificated lead-foils with high purity and a precise thickness of 0.1 to 1.25 mm were used.The measurements in the narrow beam according to DIN EN 61 331-1 showed that nearly all aprons reach the required lead equivalent at mid-range tube voltages of 100 kV. At higher and lower tube voltages, the requirements of DIN EN 61 331-3 were largely not met. In contrast, the testing of the same aprons in inverse broad-beam geometry according to DIN 6857-1 showed that only a few aprons meet the requirements for being classified in the nominal protection class.The measurements suggest that testing method DIN 6857-1 has yet to prevail and that manufacturers are just beginning to develop the appropriate protective materials.

PACS number s : 71.10. w.-- et al., We propose graphite intercalation compounds GICs as a material system with precisely the same electronic properties as doped few layer graphene. Despite the fact that GICs have been around for the last four decades, this fact has gone unnoticed so far. Especially, we focus on the electronic energy bands of KC8 which correspond to a doped graphene monolayer. We provide extensive theoretical and experimental evidence for this claim employing a combined angle-resolved photoemission and theory approach using tight-binding, standard density-functional theory and including electron-electron correlation on a GW level. We observe a strong momentum-dependent kink in the quasiparticle dispersion at 166 meV highlighting electron-phonon coupling to an in-plane transversal optical phonon. These results are key for understanding both the unique electronic properties of doped graphene layers and superconductivity in KC8., A.G. acknowledges an APART Fellowship from the Austrian Academy of Sciences and a Marie Curie Individual Fellowship COMTRANS from the European Union. T.P. acknowledges DFG under Project No. PI 440/3/4/5. C.A. and A.R. acknowledge funding by the Spanish MEC Grant No. FIS2007-65702-C02-01 , “Grupos Consolidados UPV/EHU del Gobierno Vasco” Grant No. IT-319-07 , and the European Community through NoE Nanoquanta Grant No. NMP4-CT-2004-500198 , e-I3 ETSF Project INFRA-2007-1.2.2: Grant No. 211956 , and SANES Grant No. NMP4-CT-2006-017310 . The computer resources were provided by the Barcelona Supercomputing Center and the Basque Country University UPV/EHU SGIker Arina and ETSF. D.V. acknowledges DFG under Project No. VY64/1-1. J.F. acknowledges and appreciates financial support by the DFG Forschergruppe No. FOR 538).

Standards for medical clearance for private or business missions abroad are--at least in the German speaking countries--not clearly defined and mostly derived from the old terminus "Tropentauglichkeit" which means fit for mission in the tropics. The authors now define a new standard, called "Entsendungstauglichkeitsuntersuchung" which means clearance of fitness for all types of missions abroad, independent of distinct climatic zones. To meet the inhomogenous requirements of different institutions and different types of missions the medical examination proposed follows a modular structure to optimize economic and medical use of resources. Moreover, as Austria, Germany and Switzerland have different legal and economic postulates, the medical examination has to be adapted to the different premises. The definition and description of this special type of "medical clearance for missions abroad" is supplemented by recommendations for definitions of clients who should undergo such an investigation and the professionals who should perform this type of investigation. Additionally, results of this type of medical clearance are defined and prophylactic aspects in terms of pre-travel advice are mentioned.

We report on a detailed study of the filling factor and electronic structure of the trimetal nitride fullerene ${\mathrm{Dy}}_{3}\mathrm{N}@{\mathrm{C}}_{80}(\mathrm{I})$ filled single-wall carbon nanotubes (SWCNTs), the so-called endohedral peapods $({\mathrm{Dy}}_{3}\mathrm{N}@{\mathrm{C}}_{80}@\mathrm{SWCNTs})$, using photoemission spectroscopy as a probe. The photoemission response close to the Fermi energy exhibits the manifestation of one-dimensional electronic structures, i.e., van Hove singularities and a power-law (Tomonaga-Luttinger liquid) behavior. Within the experimental accuracy the spectral shapes are the same as those of the pristine SWCNTs reference sample. From a comparison between the valence-band spectra of the peapods and the SWCNT measured with $400\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ photon energy, we determine the bulk filling of ${\mathrm{Dy}}_{3}\mathrm{N}@{\mathrm{C}}_{80}@\mathrm{SWCNTs}$ to be $74\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.2em}{0ex}}%$. In addition, from a detailed analysis of the resonant photoemission across the Dy $4d\text{\ensuremath{-}}4f$ edge, we show that the effective Dy valency of ${\mathrm{Dy}}_{3}\mathrm{N}@{\mathrm{C}}_{80}@\mathrm{SWCNTs}$ is about 3.0 which is slightly larger than for ${\mathrm{Dy}}_{3}\mathrm{N}@{\mathrm{C}}_{80}$.

We report on the doping dependence of the electronic structure of the valence band of mats of single wall carbon nanotubes (SWCNT) using high resolution photoemission spectroscopy as probe. For the pristine SWCNT about one third are metallic Tomonaga‐Luttinger‐Liquids (TLL) which is directly related to a power law scaling in the density of states. The changes in the valence band of these doped one dimensional nanostructures explicitly show the effect of the dimensionality on the electronic structure. At low doping we observe a crossover from a TLL behavior to a normal Fermi liquid whereas at high doping levels at low binding energy a Fermi level is found.

We report on studies of the n‐type doping dependence of the Raman response of double‐wall carbon nanotubes (DWCNT). The G‐line is found to be shifting upon doping. The direction of the shift depends on if the exciting laser light is in resonance with mainly inner or outer tubes. The RBM response upon doping shows that a charge transfer from the dopant happens predominantly to the outer tubes at low doping. Charge transfer to the inner tubes occurs at higher doping levels. Charge transfer to the inner component is also shown to be starting earlier to the inner tube in DWCNT than to C60 in peapods.

We report a study of the electronic structure and charge transfer in the metallofullerene Sc 3 N@C 8 0 using photoemission and x-ray absorption spectroscopy. Through a comparison of the x-ray absorption spectrum of Sc 3 N@C 8 0 at the Sc L 2 , 3 edge with atomic multiplet calculations, the Sc 3d electron count is determined to be 0.6, thus giving an effective Sc valency of 2.4. With the N atom gaining a full electronic shell by means of covalent bonding with the Sc (also involving the Sc3d electron density observed in the x-ray absorption experiments), the remaining six valence electrons of the Sc 3 N cluster are then transferred to the carbon cage which stabilizes the C 8 0 cage structure with I h symmetry, a structure which is not energetically favored in neutral C 8 0 . The presence of the highly symmetric I h cage structure is further supported by the observation of distinct fine structure in the valence band photoemission spectra of the endohedral, which results from the high degree of effective degeneracy of the electronic states in the molecule. Finally, the results of investigations of K-doped Sc 3 N@C 8 0 using photoemission give insight into the K x Sc 3 N@C 8 0 phases that are formed upon intercalation.

We report recent measurements of the electronic and structural properties of bulk samples of ${\mathrm{C}}_{60}$ molecules encapsulated in single-wall carbon nanotubes (so-called peapods) using electron-energy-loss spectroscopy in transmission. We demonstrate that ${\mathrm{C}}_{60}$ peapods with a single-wall carbon nanotube (SWNT) diameter distribution of $1.37\ifmmode\pm\else\textpm\fi{}0.08 \mathrm{nm}$ have an average fullerene filling of 60%. Regarding the electronic and optical properties, the overall shape of the response of the SWNT and the peapods is very similar, but with distinct differences in the fine structure. The interband transitions of the SWNT are slightly downshifted in the peapods, which can be explained by either a small increase of the SWNT diameter or by a change of the intertube interaction. The electronic and optical properties of the encapsulated ${\mathrm{C}}_{60}$ peas closely resemble those of solid fcc ${\mathrm{C}}_{60}$ showing small changes in the relative intensities, peak positions, and peak width, which point to a weak van der Waals interaction between the tubes and the encapsulated fullerenes.

We report on the charge transfer in intercalated C60 peapods as a function of doping. A competition between a charge transfer to the SWCNT pods and one to the C60 peas is observed. At low intercalation levels the charge transfer is predominantly to the SWCNT pods. This leads to a shift of the Fermi level beyond the third van Hove singularity of the semiconducting tubes for potassium intercalation (n‐doping) and beyond the first singularity of the metallic tubes for FeCl3 intercalation (p‐doping), respectively. In addition at high levels of potassium intercalation the C60 pods are charged up to C606− and form a metallic one dimensional polymer.

Recently, it was possible to fill single wall carbon nanotubes with C60 fullerenes resulting in carbon structures with new and interesting properties (so‐called C60 peapods). All Raman allowed modes of the free C60 were identified for the encaged C60. In this contribution we demosntrate how the concentration of the peas in the SWCNT pods can be obtained from a detailed analysis of the Raman spectra of the peapods.

Doping induced polymerization of C(60) inside single-walled carbon nanotubes is reported using Raman spectroscopy and resistivity measurements as a probe. The resistivity changes from semiconducting for the undoped system to metallic for the doped system. For full intercalation, we observe a chemical reaction inside the nanotubes which leads to a one-dimensional polymeric C(60)(-6) chain which has metallic character. The resonance and the oscillations of the radial breathing mode are lost suggesting an up-shift of the Fermi level to beyond the third Van Hove singularity in the semiconducting tubes. The linewidth of the radial breathing mode now represents directly the Gaussian distribution of tube diameters.

We have studied the electronic structure and charge transfer properties of the monometallofullerene Sc3N@C80 using photoemission spectroscopy. In this metallofullerene the C80 cage with Ih symmetry is stabilised by the inclusion of the Sc3N unit. Investigation of the pristine material using core level photoemission shows a strong, symmetric broadening of the C1s line compared to C60 and a chemical shift of the Sc 2p doublet equivalent to that in Sc2@C84. This is a first hint for a similar charge transfer from the Sc ions in Sc3N@C80 and Sc2@C84. The valence band photoemission shows a distinct fine structure and an onset of the HOMO at about 1 eV binding energy. This clearly indicates a closed shell structure. Finally, we also present first photoemission studies of the combinational doping of the Sc3N@C80 system, here realized via potassium intercalation.

Conditional on the fabrication process, SWCNTs appear mostly as bundles of varying diameters. In this paper, the resulting distributions of bundle diameters, determined by Raman spectroscopy and by AFM tapping mode are compared directly.

Photoselective resonance Raman scattering is well known for C60 and pristine SWNTs and has been extensively studied. In this contribution we present a detailed study of the photoselective resonance Raman scattering for C60 encapsulated in single wall carbon nanotubes (SWNTs), so-called C60 peapods, when excited with 13 different laser lines. For the Ag(2) pinch mode of C60, which is most sensitive to resonance scattering, we observe a downshift of the main Raman resonance energy to lower energy. Interestingly a second component has an additional resonance in the optical gap of C60 at around 1.8 eV. The resonance scattering of the SWNT radial breathing mode (RBM) and G-line are only slightly changed compared to the pristine SWNT reference.

We report on the vibronic structure of the single bonded charged fullerene dimers (C59N)2 and (C60−)2 in comparison to pristine C60. Raman spectra of (C60−)2 were measured and compared to spectra from (C59N)2 and C60. Observation and analysis concentrates on the low energy modes. Both dimers exhibit a dramatic resonance below 800 cm−1 for red laser excitation. Intercage modes were only observed for the dimers. Their response was lost at the transformation of (C60−)2 to the polymer.

In this contribution we present a study of the electronic properties of Gd@C82 using high energy spectroscopy. From UPS we find a close similarity to La@C82. From the analysis of the valence band and core level spectra excited using x-ray radiation, we conclude that the Gd-ion has transferred three electrons to the C82 cage, although there are signs of hybridisation between the C82 cage and the rare earth ion.

In this contribution we present the momentum-dependent dielectric response function of multi-wall carbon nanotubes (MWNTs) measured using electron energy-loss spectroscopy (EELS) in transmission. Of particular interest here is the dispersion relation of the π-plasmon, which represents the collective excitation of the π-electron system. At high momentum transfer the plasmon dispersion in the MWNTs parallels that of graphite, whereas in the long-wavelength-limit a significant reduction of the plasmon energy is observed. This can be understood as a consequence of the one-dimensionality of the π-electron system in the MWNTs indicating a suppression of the electron-electron Coulomb interaction at low momenta due to the spatial confinement of the electrons.

We have studied electron diffracion and core-level excitations of C 60 molecules encapsulated in single-wall carbon hanotubes, so-called, peapods, by electron energy-loss spectroscopy in transmission. The overall shape of the response of the single wall nanotube and the peapods is very similar but with distinct differences in the fine structure. The filling factor of C 60 peapods can be estimated with our volume-sensitive probe.

Summary form only given. In situ IR-reflectivity measurements are reported for K and Rb doped C/sub 60/ films and single crystals. In the spectral range of the four F/sub 1u/ modes we analysed the change of these modes as a function of doping. By iterative doping and annealing processes we obtained nearly pure phases of A/sub x/C/sub 60/ (x = 0, 1, 3, 4, 6). A quantitative analysis of the reflectivity spectra using a multilayer response function revealed the line positions, linewidth and the oscillatorstrength for the F/sub 1u/ modes. The second lowest mode and the highest mode showed good agreement with the charged phonon model with respect to line shift and absorption intensity.

We report 13C nuclear magnetic resonance measurements on 13C-enriched single-wall carbon nanotube (SWCNT) bundles. The temperature dependence of the nuclear spin-lattice relaxation rate, 1/T1, exhibits a power law variation, as expected for a Tomonaga-Luttinger liquid (TLL). The observed exponent is smaller than that expected for the two-band TLL model. A departure from the power law is observed only at low T, where thermal and electronic Zeeman energy merge. Extrapolation to zero magnetic field indicates gapless spin excitations. The wide T range on which power law behaviour is observed suggests that SWCNT is so far the best realization of a one-dimensional quantum metal.