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Infrared spectroscopy. --- Raman spectroscopy.

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This thesis identifies the turning point in chain length, after which alkanes self-solvate into a folded structure instead of an extended stretched conformation. After this turning point, London dispersion forces rearrange isolated n-alkanes into a particular hairpin-structure, while for shorter chain lengths, a simple stretched conformation is energetically preferred. This thesis can locate the experimental turning point for the first time in an interaction-free manner from measurements of unbranched alkanes at low temperatures in supersonic jet expansions. It contains a detailed analysis of the vibrational Raman spectra of the chain molecules, which is supported by comprehensive quantum chemical simulations. In this way, the detailed balance between inter-chain attraction and conformational flexibility can be quantified.The investigations are complemented by measurements of perfluoroalkanes, and similarities and differences between the compounds are discussed. Furthermore, Nils Lüttschwager determines the stiffnesses (elastic moduli) of two of the most common industrial polymers: polyethylene and polytetrafluorethylene. He uses in this thesis a sophisticated extrapolation to calculate this value from quantities of their building blocks, showing that the single polymer molecules can be as stiff as a rod of steel.

Raman spectroscopy. --- Conformational analysis. --- Cryochemistry. --- Low temperature chemistry --- Thermochemistry --- Analysis, Conformational --- Molecular rotation --- CARS spectroscopy --- Coherent anti-Stokes Raman spectroscopy --- Spectroscopy, Raman --- Spectrum analysis --- Chemistry, Physical organic. --- Spectroscopy. --- Polymers. --- Physical Chemistry. --- Atomic/Molecular Structure and Spectra. --- Spectroscopy/Spectrometry. --- Polymer Sciences. --- Polymere --- Polymeride --- Polymers and polymerization --- Macromolecules --- Analysis, Spectrum --- Spectra --- Spectrochemical analysis --- Spectrochemistry --- Spectroscopy --- Chemistry, Analytic --- Interferometry --- Optics --- Radiation --- Wave-motion, Theory of --- Absorption spectra --- Light --- Spectroscope --- Chemistry, Physical organic --- Chemistry, Organic --- Chemistry, Physical and theoretical --- Qualitative --- Physical chemistry. --- Atomic structure  . --- Molecular structure . --- Polymers  . --- Spectrometry --- Structure, Molecular --- Chemical structure --- Structural bioinformatics --- Structure, Atomic --- Atomic theory --- Chemistry, Theoretical --- Physical chemistry --- Theoretical chemistry --- Chemistry --- Analytical chemistry

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Neutrinos can arguably be labeled as the most fascinating elementary particles known as their small but non-zero rest mass points to new mass generating mechanisms beyond the Standard Model, and also assigns primordial neutrinos from the Big Bang a distinct role in shaping the evolution of large-scale structures in the universe. The open question of the absolute neutrino mass scale will be addressed by the Karlsruhe Tritium Neutrino (KATRIN) experiment, currently under construction. This thesis reports major contributions to developing and implementing new laser-spectroscopic precision tools to continuously monitor the isotope content of the windowless gaseous tritium source of KATRIN. The method of choice, Raman spectroscopy, is ideally suited for in-situ monitoring of all six hydrogen isotopologues. In a series of beautiful experiments the author obtained two independent novel calibration methods, first based on a comparison of experimental Raman depolarization ratios with corresponding quantum-chemical calculations, and second on a gas sampling technique. Both methods yield consistent cross-calibration results and, as well as yielding improvements in precision, will be of major importance in reducing systematic effects in long-term neutrino mass measurements. The methods developed in this thesis also have great potential to further broaden the applications of Raman spectroscopy to study extended sources such as in atmospheric physics. .

Raman spectroscopy. --- Calibration. --- Physical measurements --- Standardization --- CARS spectroscopy --- Coherent anti-Stokes Raman spectroscopy --- Spectroscopy, Raman --- Spectrum analysis --- Quantum theory. --- Elementary Particles, Quantum Field Theory. --- Atomic/Molecular Structure and Spectra. --- Spectroscopy and Microscopy. --- Quantum dynamics --- Quantum mechanics --- Quantum physics --- Physics --- Mechanics --- Thermodynamics --- Elementary particles (Physics). --- Quantum field theory. --- Atomic structure  . --- Molecular structure . --- Spectroscopy. --- Microscopy. --- Analysis, Microscopic --- Light microscopy --- Micrographic analysis --- Microscope and microscopy --- Microscopic analysis --- Optical microscopy --- Optics --- Analysis, Spectrum --- Spectra --- Spectrochemical analysis --- Spectrochemistry --- Spectrometry --- Spectroscopy --- Chemistry, Analytic --- Interferometry --- Radiation --- Wave-motion, Theory of --- Absorption spectra --- Light --- Spectroscope --- Structure, Molecular --- Chemical structure --- Structural bioinformatics --- Structure, Atomic --- Atomic theory --- Relativistic quantum field theory --- Field theory (Physics) --- Quantum theory --- Relativity (Physics) --- Elementary particles (Physics) --- High energy physics --- Nuclear particles --- Nucleons --- Nuclear physics --- Qualitative --- Analytical chemistry