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In this work new Raman spectroscopic experiments on rare earth metal-rare earth trihalide melts (Ln-LnX3 and LnX2-LnX3: Ln=Ce, Nd; X=Cl, I) and their mixtures in alkali halide eutectic solvents ((LiX-KX)eu; X=Cl, I) are presented. The main results can be summarized as follows:- The Raman spectra of following trihalide systems have been measured for the first time: CeCl3, CeI3, NdI3 and their mixtures in the respective alkali halide eutectic solvent. The structure of the LnX3 in the solvent can be characterized by octahedral complexes. The force constants decrease from the chlorides to the iodides. - The Raman spectra of the following dihalides have been observed in this work: NdCl2, CeI2 and their mixtures in the alkali halide solvent. Interestingly, CeCl2 might form as intermediate species on doping CeCl3 with Ce. It is not a stable compound in the Ce-CeCl3 phase diagram.- With respect to the above mentioned main objective the following conclusions can be drawn: (i) On mixing of NdCl2 with NdCl3 in (LiCl-KCl)eu the undisturbed spectra of both components can be observed simultaneously. This is in agreement with the suggested intervalence charge transfer hopping mechanism if one assumes a hopping rate below 1012.(ii) Even though CeCl2 might form as intermediate, in the equilibrium spectra of liquid Ce-CeCl3-(LiCl-KCl)eu only the typical - 36 CeCl -octahedra can be identified. This supports the assumption that in these systems the electronic defect states are probably mobile Drude-like electrons which do not lead to new Raman detectable species. A qualitatively similar observation was made for CeI2-CeI3-(LiI-KI)eu melts.

Seltenerdhalogenide --- Hochtemperatur --- Raman-Spektroskopie

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In this work new Raman spectroscopic experiments on rare earth metal-rare earth trihalide melts (Ln-LnX3 and LnX2-LnX3: Ln=Ce, Nd; X=Cl, I) and their mixtures in alkali halide eutectic solvents ((LiX-KX)eu; X=Cl, I) are presented. The main results can be summarized as follows:- The Raman spectra of following trihalide systems have been measured for the first time: CeCl3, CeI3, NdI3 and their mixtures in the respective alkali halide eutectic solvent. The structure of the LnX3 in the solvent can be characterized by octahedral complexes. The force constants decrease from the chlorides to the iodides. - The Raman spectra of the following dihalides have been observed in this work: NdCl2, CeI2 and their mixtures in the alkali halide solvent. Interestingly, CeCl2 might form as intermediate species on doping CeCl3 with Ce. It is not a stable compound in the Ce-CeCl3 phase diagram.- With respect to the above mentioned main objective the following conclusions can be drawn: (i) On mixing of NdCl2 with NdCl3 in (LiCl-KCl)eu the undisturbed spectra of both components can be observed simultaneously. This is in agreement with the suggested intervalence charge transfer hopping mechanism if one assumes a hopping rate below 1012.(ii) Even though CeCl2 might form as intermediate, in the equilibrium spectra of liquid Ce-CeCl3-(LiCl-KCl)eu only the typical - 36 CeCl -octahedra can be identified. This supports the assumption that in these systems the electronic defect states are probably mobile Drude-like electrons which do not lead to new Raman detectable species. A qualitatively similar observation was made for CeI2-CeI3-(LiI-KI)eu melts.

Seltenerdhalogenide --- Hochtemperatur --- Raman-Spektroskopie

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Spektrale Analysen liefern Informationen zur Auslegung eines kamerabasierten Überwachungssystems für gepulste Laserschweißprozesse. Aufbauend auf diesen prozessphysikalischen Erkenntnissen wird ein bildbasiertes, schwach-überwacht lernendes Klassifikationssystem zur industriellen Prozessüberwachung anhand der Prozessabstrahlung entwickelt. Der Einsatz einer schmalbandigen Beleuchtung sowie divergenzbasierter Kantendetektionsfilter ermöglicht die Segmentierung der Prozesszonenoberfläche.

Laserstrahlschweißen --- Klassifikation --- Spektroskopie --- divergenzbasierte Kantendetektion --- Prozessüberwachung

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This work focusses on the first demonstration of silicon light-emitting diodes (SiLEDs) based on silicon nanocrystals as light emitting material. In a detailed study we characterize the optoelectronic and morphological properties of the SiLEDs. In addition, a whole set of new fields of applications of silicon nanocrystals, such as biomedical approaches or direct laser sintering, and detailed spectroscopic study of the particles complete the work.

Spektroskopie --- Silizium-Nanokristalle --- Quantenpunkte --- Optoelektronik --- Organische Leuchtdioden

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Der Ablauf von Verbrennungsprozessen wird erheblich durch die Reaktionskinetik kurzlebiger Intermediate bestimmt. Die vorliegende Arbeit beschäftigt sich einerseits mit der Bildungskinetik von CN-Radikalen in Zündfunken, deren Lumineszenz für diagnostische Verfahren herangezogen wird und zum anderen mit den Reaktionen von OH-Radikalen mit den Rußvorläufern Diacetylen und Vinylacetylen. Zur Untersuchung der beiden Teilaspekte kommen spektroskopische Methoden zum Einsatz.

Spektroskopie --- Chemische Kinetik --- Laserinduzierte Fluoreszenz --- Hydroxyl-Radikale (OH) --- Zündfunken