THE THERMAL SELF-POLYMERIZATION OF METHYL METHACRYLATE - ROTATIONAL CHARACTERIZATION OF THE METHYL METHACRYLATE DIMER (IT'S NOT A COMPLEX!)

\vspace{-1in} \begin{wrapfigure}[0]{r}{430pt} \includegraphics[scale=0.5]{verybright66.eps} \end{wrapfigure} \vspace{1in} Structural data from microwave spectra of monomers and oligomers of the methyl methacrylate system compared to theoretical predictions allows for accurate predictions of the structure and physical properties of higher oligomers or even polymers. The idea behind this project is to start with small building blocks and to successively increase the size of the oligomers in order to obtain more and more accurate predictions. Following the previous analysis of the monomer, this contribution focuses on the dimer of methyl methacrylate.\newline In the dimer phase of methyl methacrylate, which was subjected to a thermal self-polymerization process, the linear methyl methacrylate dimer was identified by means of rotational spectroscopy. The analysis was performed using the coaxially oriented beam-resonator arrangement Fourier-transform microwave (COBRA-FTMW) spectrometer. The dimer comprises three methyl rotors. Coupling of the methyl internal rotation to the overall rotation causes a complicated, challenging splitting of the rotational spectrum. The fact that only the two methoxymethyl groups contributed resolvable \mbox{($>$5kHz)} splittings simplified the spectrum a little and a fit of molecular parameters to the experimental data was achieved with experimental accuracy utilizing the program XIAM. \vspace{.5in} \mbox{

HAVING A BALL! MICROWAVE SPECTRUM OF THE (NEARLY) SPHERICAL TOP TEFLIC ACID

The microwave spectrum of teflic acid (\chem{TeF_5OH}) in the range of \mbox{3 to 25\,GHz} was analyzed. Though teflic acid is an asymmetric top in its equilibrium structure, it behaves like a symmetric top because of the OH group internal rotation. The strongest transitions in the spectrum originate from the \chem{^{130}TeF_5OH}, \chem{^{128}TeF_5OH} and \chem{^{126}TeF_5OH} species as shown in the figure below. The \chem{TeF_5{}^{18}OH}, \chem{TeF_5OD} and \chem{TeF_5{}^{18}OD} isotopologues were also analyzed. From the rotational constants of the different istopologues and with help of quantum chemical calculations a semi empirical equilibrium structure of teflic acid was determined. The \mbox{Te-O} equilibrium bondlength was determined with accuracy to the hundredth of an angstrom. \mbox{} \begin{wrapfigure}[0]{r}[-90pt]{0pt} \includegraphics[scale=0.70]{Transition.eps} \end{wrapfigure} \vspace{1.5in} \mbox{

Xe⋯OCS: Relatively straightforward?

We report a benchmark-quality equilibrium-like structure of the Xe⋯OCS complex, obtained from microwave spectroscopy. The experiments are supported by a wide array of highly accurate calculations, expanding the analysis to the complexes of He, Ne, Ar, Kr, Xe, and Hg with OCS. We investigate the trends in the structures and binding energies of the complexes. The assumption that the structure of the monomers does not change significantly upon forming a weakly bound complex is also tested. An attempt at reproducing the r(2)m structure of the Xe⋯OCS complex with correlated wavefunction theory is made, highlighting the importance of relativistic effects, large basis sets, and inclusion of diffuse functions in extrapolation recipes

Reactivity and rotational spectra: The old concept of substitution effects

The internal rotation of methyl groups and nuclear quadrupole moments of the halogens Cl, Br, I in o-halotoluenes cause complex spectral fine and hyperfine structures in rotational spectra arising from angular momentum coupling. Building on the existing data regarding o-fluorotoluene and o-chlorotoluene, the investigations of o-bromotoluene and o-iodotoluene allow for a complete analysis of the homologous series of o-halogenated toluenes. The trend in the methyl barriers to internal rotation rising with the size of the halogen can be rationalised by repulsion effects as predicted by MP2 calculations. Furthermore, the analysis of the observed quadrupole coupling serves as a quantitative intra-molecular probe, e.g. for the explanation of the relative reaction yields in the nitration of halotoluenes, related to the different π-bond character of the C-X bond depending on the position of substitution

A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined

Kombination von Augmented/Mixed-Reality-Systemen mit weiteren digitalen Technologien

Die Instandhaltung von Gebäuden im Infrastrukturbereich ist aus finanziellen und wirtschaftlichen Gründen von großer Bedeutung. Insbesondere bei Brücken ist es wichtig, die Instandhaltungskosten im Auge zu behalten. Die frühzeitige Erkennung von Schäden und deren frühzeitige Behebung ermöglicht es, den Aufwand für Erhaltungsmaßnahmen zu begrenzen. Die Verfolgung des Schadensverlaufs kann nur durch regelmäßige und häufige Begehungen durch Sachverständige erfolgen, die ihre Befunde in der Regel manuell dokumentieren. Ziel dieses Forschungsvorhabens ist es, ein Konzept für ein Brückeninspektionstool vorzustellen, prototypisch umzusetzen und zu evaluieren. Das Brückeninspektionstool wird mehrere Arten von Hardware-Geräten verwenden, um das Brückeninspektionspersonal bei der Beurteilung und Dokumentation von Schäden zu unterstützen, wobei Kombinationen aus Künstlicher Intelligenz und Mixed Reality Technologien eingesetzt werden. Hierfür wurden Interviews mit Bauwerksprüfenden aus verschiedenen Unternehmen und Branchen durchgeführt, um wichtige Anforderungen zu ermitteln. Auf der Grundlage dieser Anforderungen wurde ein Konzept entwickelt, das mit bestehenden Datenbanken für Infrastrukturen kompatibel ist. Weiter wurde das Konzept prototypisch in einen Demonstrator umgesetzt, welcher Informationen über die Künstliche Intelligenz sammelt und mithilfe der Mixed Reality Technologien anzeigt. Hierfür wurde sowohl eine Augmented Reality Anwendung zur Anzeige der gesammelten Informationen, sowie eine Tablet Anwendung zur Datenspeicherung entwickelt. Weiter wurde die entwickelte Künstliche Intelligenz auf einem selbsterstellten Datensatz trainiert, um Schäden erkennen und klassifizieren zu können. Der erstellte Demonstrator wurde unter realen Bedingungen an einem realen Bauwerk von Brückenprüfenden getestet und evaluiert. Die Ergebnisse der Tests zeigen großes Potential für den Einsatz von Künstlicher Intelligenz und Mixed Reality Technologien, wie im vorgestellten Demonstrator, für Bauwerksprüfungen. Besonders hoch wird das Potenzial der Künstlichen Intelligenz zur Detektion von Schäden gewertet.Early detection of damage to bridges is very important for financial and environmental reasons. This can only be achieved by regular and frequent inspections by experts, who usually document their findings by hand. The aim of this research project is to present a concept for a bridge inspection tool, as well as prototype and evaluate the presented concept. The bridge inspection tool will use several types of hardware devices to assist bridge inspection personnel in assessing and documenting damages, using combinations of artificial intelligence and mixed reality technologies. For this purpose, interviews were conducted with structural inspectors from various companies and industries to identify key requirements. Based on these requirements, a concept was developed that is compatible with existing databases for infrastructures. Further, the concept was prototypically implemented in a demonstrator, which collects information with the help of artificial intelligence and displays it using mixed reality technologies. For this purpose, both an augmented reality application for displaying the collected information and a tablet application for data storage were developed. Further, the developed Artificial Intelligence was trained on a self-created dataset to be able to detect and classify damages. The implemented demonstrator was tested and evaluated under real conditions on a real structure by bridge inspectors. The results of the tests show great potential for the use of Artificial Intelligence and Mixed Reality technologies, as presented in the demonstrator, for structural inspections. The potential of Artificial Intelligence for damage detection was rated particularly high

A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined. © 2020 The Authors. Published by Wiley-VCH Gmb

Untersuchung molekularer Strukturparameter und interner Dynamik mittels hochaufgelöster Molekularstrahl-Fourier-Transform-Mikrowellen-Spektroskopie

In this thesis the first microwave spectroscopic investigations of methyl methacrylate (MMA) and methacrylic acid (MAA) and their s--trans and s--cis conformers as well as of the covalently bonded MMA dimer of thermal self-polymerization are described. In addition, all singly substituted heavy atom isotopologues of MMA monomer and MAA, were measured in their natural abundance. Due to the internal rotation of methyl groups, the microwave spectra are extremely complex. The coupling of the internal rotation to the overall rotation was successfully treated with the combined-axis-method (CAM) implemented in the program XIAM. In addition, the very flat potential hypersurface of the MMA dimer leads to a very flexible molecule and the quantum-chemically predicted equilibrium structures vary tremendously between different methods. This makes the dimer experimental data perfect for benchmarking procedures. A novel approach to comparing quantum-chemical methods with a small data set suggests that CAM-B3LYP-D3BJ/aug-cc-pVTZ is an excellent method for the investigated molecules and similar systems. After this initial benchmarking, combinations of microwave data with CAM-B3LYP-D3BJ vibrational corrections were formulated to determine the equilibrium structures of the species with for MMA and MAA unprecedented sub-pm accuracy. The structures were determined following two approaches. On the one hand Kraitchman's equations were used (r_{s-->e,SE}) and on the other hand a fit of internal structural parameters to experimental rotational constants was performed (r_{0-->e,SE}). Synthetic data studies have shown that, r_{0-->e,SE} is the more accurate equilibrium structure for the investigated molecules. The difference to r_{s-->e,SE} may be interpreted as an indicator for the quality. The accuracy of the presented structures is so high, that they should be used in benchmarking procedures of the most sophisticated quantum-chemical methods. This is exemplified for the methods CAM-B3LYP-D3BJ/aug-cc-pVTZ and B3LYP-D3/aug-cc-pVTZ, both of which show significant deviations from the determined equilibrium structures. The results of the studies will be useful in future investigations of the trimer of MMA and higher oligomers. These should be well predicted using the CAM-B3LYP-D3BJ method and have similar barriers to internal rotation as the dimer. If the trimer also shows good agreement with the quantum-chemical predictions, CAM-B3LYP-D3BJ (or a derived force field in molecular mechanics simulations) could be tested for the reproduction of macroscopic properties known from experimental studies in the literature, e.g. density of monomer and dimer or the shear modulus of the polymer. If this is successful and agreement is also found for the macroscopic properties of the condensed phase, other systems might be treated similarly, even if the macroscopic properties are not known experimentally.In dieser Arbeit werden die ersten mikrowellenspektroskopischen Untersuchungen von Methylmethacrylat (MMA) und Methacrylsäure (MAA) und deren s--trans- und s--cis-Konformeren sowie des kovalent gebundenen MMA-Dimers der thermischen Selbstpolymerisation beschrieben. Darüber hinaus wurden alle einfach an den schweren Atomen substituierten Isotopologen von MMA-Monomer und MAA in ihrer natürlichen Häufigkeit gemessen. Aufgrund der internen Rotation von Methylgruppen sind die Mikrowellenspektren sehr komplex. Die Kopplung der internen Rotation an die Gesamtrotation wurde erfolgreich mit der im Programm XIAM implementierten kombinierten-Achsen-Methode (CAM) behandelt. Darüber hinaus führt die sehr flache Potential-Hyperfläche des MMA-Dimers zu einem sehr flexiblen Molekül und die quantenchemisch vorhergesagte Gleichgewichtsstruktur variiert zwischen verschiedenen Methoden enorm. Damit sind die experimentellen Daten des Dimers perfekt für Benchmarking-Prozeduren geeignet. Ein neuartig vorgestellter Ansatz zum Vergleich quantenchemischer Methoden anhand eines kleinen Datensatzes, lässt darauf schließen, dass CAM-B3LYP-D3BJ/aug-cc-pVTZ eine für die untersuchten Moleküle und ähnliche Systeme ausgezeichnet geeignete Methode ist. Nach diesem anfänglichen Benchmarking wurden Kombinationen von Mikrowellendaten mit CAM-B3LYP-D3BJ-Schwingungskorrekturen formuliert, um die Gleichgewichtsstrukturen der Spezies zu bestimmen. Diese weisen eine für MMA und MAA bisher unerreichte sub-pm Genauigkeit auf. Die Strukturen wurden zwei Ansätzen folgend bestimmt. Zum einen wurden Kraitchmans Gleichungen verwendet (r_{s-->e,SE}), zum anderen wurde eine Anpassung von internen Strukturparametern zur Annäherung der experimentellen Rotationskonstanten durchgeführt (r_{0-->e,SE}). Untersuchungen an synthetischen Daten zeigten, dass die r_{0-->e,SE} als bevorzugte Gleichgewichtsstruktur für die hier betrachteten Moleküle zu empfehlen ist. Die Differenz zur r_{s-->e,SE} kann als ein Qualitätsindikator interpretiert werden. Die Genauigkeit der präsentierten Strukturen ist so hoch, dass sie in Benchmarking-Prozeduren der genausten quantenchemischen Rechenmethoden genutzt werden sollten. Dies ist beispielhaft für die Methoden CAM-B3LYP-D3BJ/aug-cc-pVTZ und B3LYP-D3/aug-cc-pVTZ gezeigt, die beide signifikante Abweichungen von den ermittelten Gleichgewichtsstrukturen zeigen. Die Ergebnisse der Untersuchungen werden insbesondere bei zukünftigen Untersuchungen des Trimers von MMA und höheren Oligomeren von Nutzen sein. Diese sollten mit der CAM-B3LYP-D3BJ-Methode gut vorhergesagt werden können und ähnliche Barrieren für die interne Rotation wie das Dimer aufweisen. Wenn das Trimer ebenfalls eine gute Übereinstimmung mit der quantenchemischen Vorhersage zeigt, könnte CAM-B3LYP-D3BJ (oder ein abgeleitetes Kraftfeld in molekular mechanischen Simulationen) auf die Reproduktion makroskopischer Eigenschaften getestet werden, die aus experimentellen Untersuchungen in der Literatur bekannt sind, z. B. Dichte von Monomer und Dimer oder das Schermodul des Polymers. Wenn dies gelingt und gute Übereinstimmung auch für die makroskopischen Eigenschaften der kondensierten Phasen erzielt wird, liegt es nahe, dass andere Systeme auf ähnliche Weise behandelt werden können, selbst wenn die makroskopischen Eigenschaften nicht experimentell bekannt sind

HAVING A BALL! MICROWAVE SPECTRUM OF THE (NEARLY) SPHERICAL TOP TEFLIC ACID

The microwave spectrum of teflic acid (\chem{TeF_5OH}) in the range of \mbox{3 to 25\,GHz} was analyzed. Though teflic acid is an asymmetric top in its equilibrium structure, it behaves like a symmetric top because of the OH group internal rotation. The strongest transitions in the spectrum originate from the \chem{^{130}TeF_5OH}, \chem{^{128}TeF_5OH} and \chem{^{126}TeF_5OH} species as shown in the figure below. The \chem{TeF_5{}^{18}OH}, \chem{TeF_5OD} and \chem{TeF_5{}^{18}OD} isotopologues were also analyzed. From the rotational constants of the different istopologues and with help of quantum chemical calculations a semi empirical equilibrium structure of teflic acid was determined. The \mbox{Te-O} equilibrium bondlength was determined with accuracy to the hundredth of an angstrom. \mbox{} \begin{wrapfigure}[0]{r}[-90pt]{0pt} \includegraphics[scale=0.70]{Transition.eps} \end{wrapfigure} \vspace{1.5in} \mbox{

THE THERMAL SELF-POLYMERIZATION OF METHYL METHACRYLATE - ROTATIONAL CHARACTERIZATION OF THE METHYL METHACRYLATE DIMER (IT'S NOT A COMPLEX!)

\vspace{-1in} \begin{wrapfigure}[0]{r}{430pt} \includegraphics[scale=0.5]{verybright66.eps} \end{wrapfigure} \vspace{1in} Structural data from microwave spectra of monomers and oligomers of the methyl methacrylate system compared to theoretical predictions allows for accurate predictions of the structure and physical properties of higher oligomers or even polymers. The idea behind this project is to start with small building blocks and to successively increase the size of the oligomers in order to obtain more and more accurate predictions. Following the previous analysis of the monomer, this contribution focuses on the dimer of methyl methacrylate.\newline In the dimer phase of methyl methacrylate, which was subjected to a thermal self-polymerization process, the linear methyl methacrylate dimer was identified by means of rotational spectroscopy. The analysis was performed using the coaxially oriented beam-resonator arrangement Fourier-transform microwave (COBRA-FTMW) spectrometer. The dimer comprises three methyl rotors. Coupling of the methyl internal rotation to the overall rotation causes a complicated, challenging splitting of the rotational spectrum. The fact that only the two methoxymethyl groups contributed resolvable \mbox{($>$5kHz)} splittings simplified the spectrum a little and a fit of molecular parameters to the experimental data was achieved with experimental accuracy utilizing the program XIAM. \vspace{.5in} \mbox{