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Additive Fertigungsverfahren wie das „laserbasierte Pulverbettschmelzen“ bieten durch ihre Eigenschaften (generativ, digital und direkt) eine Vielzahl von Moglichkeiten zur Herstellung von Kleinserien. Gleichzeitig sind dem In-Prozess nicht additive Fertigungsschritte, z. B. zur Oberflachenbearbeitung nachgelagert. Diese und weitere Post-Prozess-Arbeitsschritte konnen, neben der additiven Fertigung, sehr zeitaufwendig und kostenintensiv sein.

High resolution/low wavenumber Fourier transform Raman spectra were obtained using a combination of a rubidium vapor filter and a Ti:sapphire laser. With this setup it is possible to measure FT-Raman spectra as close as 3 cm −1 to the Rayleigh line. This is demonstrated by the Raman spectra of crystalline sulfur, cadmium iodide, mercury iodide and osmiumtetroxide.

The former major problem in conventional Raman spectroscopy in the visible range, the disturbing fluorescence of impurities, has now been eliminated: Raman spectra can be excited by light quanta in the near-infrared range, the energy of which is too low to excite fluorescence spectra. An inherent disadvantage of this technique, the v4-dependence of the intensity of the Raman radiation, is compensated for by using interferometers, which are more powerful, by a factor of several hundred, than grating spectrometers. Raman spectroscopy can now be applied to analyses of ‘real world samples’ bio materials, food, paintings, micro electronics and ‘new materials’, as well as to quality control of raw materials, to production and product control without special sample preparation. By using fiber bundles, Raman spectra can be recorded on line at the sample site, in containers and in real time. For successful recording of NIR FT Raman spectra of small samples a compromise between large lateral resolution and a large signal/noise ratio has to be found. Its theoretical base and practical approach is discussed. Confocal microscopes allow recording of NIR FT Raman spectra of small particles or inclusions. They can be coupled to the spectrometer by fiber optics, so that they may be placed at some distance from the spectrometer. By using computer-driven x-y stages, systematic mapping of the distribution of specific compounds on the surface of different samples is possible with the FT Raman microscope, as well as with the ordinary sample arrangement.

The near-infrared Fourier transform (NIR FT) Raman technique permits the measurement of Raman spectra without interference by fluorescence. Absorption by molecules containing X-H bonds in the NIR range requires a 180° scattering geometry. In this way, Raman spectroscopy of samples on surfaces is possible, both the detecting of small spots and the mapping of the sample distribution over larger areas. The spatial resolution extends into the micrometer range. Mapping of the inorganic pigment distribution of an initial letter of a mediaeval manuscript is demonstrated. For time-resolved measurements, the step-scan technique, previously developed for infrared spectroscopy, may be used in NIR FT-Raman spectroscopy as well. It allows the study of photochemical and photophysical processes, the application of modulation techniques, and the investigation of “noisy” samples. Photo-isomerization of the dye merocyanine 540 has been observed with the step-scan technique upon periodic excitation with a flash lamp.

The first Raman spectra of hydrocarbon inclusions using Fourier transform (FT) Raman microspectroscopy were obtained with a 1064 nm laser excitation in the near-infrared range (NIR FT-Raman). Some inclusions reveal the typical CH vibrational bands of organic compounds, but most of the inclusions that are fluorescent during visible Raman microspectroscopy (514 nm excitation) are still fluorescent in the NIR range. These Raman spectra are presented and compared to the conventional visible (VIS) Raman and FT-IR spectra. For spectra obtained on the same nonfluorescent inclusion, the signal/background ratio is lower in NIR FT-Raman than in VIS Raman. This ratio should be improved by application of more sensitive detectors. The increase of the power density (laser power/impact laser area) could be a future improvement in the limit of thermal background excitation and pyrolysis of the oils trapped in inclusions.

Near-infrared excited Fourier-transform Raman spectra have been obtained from different spectral forms of Rhodobacter sulfidophilus light-harvesting II complexes. This complex, when isolated in lauryldimethylamine oxide, exists in a 805–828 nm form, which can be reversibly converted to the native 805–851 nm form upon addition of salt. The FT-Raman spectra predominantly show contributions of the carotenoid in the light-harvesting complex, with small but significant contributions of the bacteriochlorophylls excited in preresonance in the Q y transition. One strongly and one weakly interacting 2a acetyl C=O group as well as one moderately strong interacting and one non-interacting 9-keto C=O carbonyl modes of the bacteriochlorophylls can be discerned for the 805–828 nm form. Changes of relative band intensities caused by different resonance conditions for the different spectral forms lead to an assignment of the strongly interacting 2a acetyl C=O and the moderately strong interacting 9 keto C=O to bacteriochlorophylls organized in the 828 pigment moiety. Shifts of these bands to higher frequencies upon the salt-induced transition indicate a perturbation of the pigment-protein interaction, probably caused by a local protein conformational change.

FT Raman spectrometry with a Nd-YAG laser (1064 nm) as the exciting light source has been used to study YBa2Cu3O7-x epitaxial thin films and ceramics. It is shown that NIR-excited Raman spectrometry can be used to distinguish various levels of oxygen content even in epitaxial thin films grown parallel to the crystallographic c-axis. A variation of the oxygen content is, in contrast to conventional, Ar-ion laser excited Raman spectra, reflected by the intensity ratio of the Ag modes near 330 cm-1 and 500 cm-1, even in the ab plane.

Just after the discovery of Raman spectroscopy in 1928, it became evident that fluorescence with a quantum yield of several orders of magnitude higher than that of the Raman effect was a great and apparently unbeatable competitor. Raman spectroscopy could therefore, in spite of many exciting advantages during the last 60 years, not be applied as an analytical routine method: for nearly every sample, fluorescing impurities had to be removed by distillation or crystallisation. Purification, however, is not possible for cells and tissues, since the removal of the fluorescing enzymes and coenzymes would destroy the cells. There is fortunately one alternative solution. When excited with the radiation of the Nd:YAG laser at 1064 nm Raman spectra are practically free of fluorescence. Raman spectra can now be recorded with minimal sample preparation. In order to facilitate non-destructive Raman spectroscopy of any sample, cells and tissues, food, textiles and works of art, a new entrance optics for Raman spectrometers is used. Typical results from several fields are demonstrated.

Fluorescence and initiation of photoreactions are problems frequently encountered with resonance Raman spectroscopy of photobiological systems. These problems can be circumvented with Fourier-transform Raman spectroscopy by using the 1064-nm wavelength of a continuous wave neodymium-yttrium/aluminum-garnet laser as the probing beam. This wavelength is far from the absorption band of most pigments. Yet, the spectra of the investigated systems--bacteriorhodopsin, rhodopsin, and phycocyanin--show that these systems are still dominated by the chromophore, or that preresonant Raman scattering is still prevalent. Only for rhodopsin were contributions of the protein and the membrane discernible. The spectra of phycocyanin differ considerably from those obtained by excitation into the UV-absorption band. The results show the usefulness of this method and its wide applicability. In addition, analysis of the relative preresonant scattering cross sections may provide a detailed insight into the scattering mechanism.

The ionization potential of CH3SCF3 and the appearance potentials of fragment ions have been measured in the photon energy range 9 -19 eV using synchrotron, radiation. From these results thermochemical data of CH3SCF3, CH3SCF3 + and fragment ions have been evaluated.

Es wird uber die Darstellung von Dichlor(trifluormethylthio)sulfonium(IV)-chlorid CF3SSCl2+Cl− berichtet. Die Identifizierung des Kations erfolgt ramanspektroskopisch unter Annahme einer Cs-Symmetrie. Dieses Salz existiert wie SCl3+Cl− nur als Festkorper, und es ist auch hinsichtlich seiner Instabilitat mit ihm vergleichbar. Dichlor(trifluoromethylthio)sulfonium(IV)-chloride CF3SSCl2+Cl− The preparation of dichloro(trifluoromethylthio)sulfonium(IV) salt CF3SSCl2+Cl− is reported. The cation is characterized by raman spectroscopy assuming a Cs-symmetry. As does SCl3+Cl− the new compound CF3SSCl2+Cl− only exists in solid state; the stabilities are comparable.

We report the matrix isolation of the sulfuranes SCl3F, SCl2F2, SClF3. They are formed in the gas phase during the cocondensation of SCl2 with ClF and F2, respectively. We measured the complete vibrational spectrum of SCl2F2, the most stable species in this series. The assignment is based on a C2v model and is supported by a normal coordinate analysis. For SCl3F and SClF3 the stretching modes are given.