Electronic spectroscopy aromaticity

A number of radical anions of sulfur-containing aromatic compounds have been studied essentially by means of ESR spectroscopy and sometimes by electronic spectroscopy. The studied compounds include aromatic rings separated by the oxidized sulfur functionality. The effects caused by the latter depend on the geometry and topology of the aromatic systems as well as on the electron-withdrawing ability of the other substituents. 

Polymer films were produced by surface catalysis on clean Ni(100) and Ni(lll) single crystals in a standard UHV vacuum system H2.131. The surfaces were atomically clean as determined from low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Monomer was adsorbed on the nickel surfaces circa 150 K and reaction was induced by raising the temperature. Surface species were characterized by temperature programmed reaction (TPR), reflection infrared spectroscopy, and AES. Molecular orientations were inferred from the surface dipole selection rule of reflection infrared spectroscopy. The selection rule indicates that only molecular vibrations with a dynamic dipole normal to the surface will be infrared active [14.], thus for aromatic molecules the absence of a C=C stretch or a ring vibration mode indicates the ring must be parallel the surface. 

The UV-visible absorption and emission spectra and excited state lifetimes of polymers are sensitive to chemical structure, polymer conformation and molecular environment and thus information concerning these properties is accessible by electronic spectroscopy measurements (4-6). One example of the application of such measurements is given in Figure 3 which illustrates the possible energy dissipation pathways which can occur in a polymer containing aromatic side groups following absorption of radiation. 

K. Kleinermanns, M. Gerhards and M. Schmitt, Electronic spectroscopy of aromatic molecules in jet-cooled hydrogen bonded clusters - structure and fluxionality, Her. Bunsen-Ges. Phys. Chem., 101 (1997) 1785-1798. 

In [483] the structure of the products of condensation of 3,5-dimethyl4-nitroisoxazole and aromatic aldehydes was investigated by NMR, IR, and electron spectroscopy. 

Relaxation Energy Shifts and Localized Molecular-Ion States in Aromatic Pendant Group Polymers. The electronic structure of polystyrene (PS) and poly vinyl pyridine (PVP) have been studied using a variety of electronic spectroscopies and model calculations (W). Here, we review the results of the UPS and ultra violet absorption spectroscopy (UAS) portion of that study, and discuss the results in a phenomenological manner. The aim of this... 

The far ultraviolet spectra of molecules are characterized by the coexistence of bands due to valence-shell (intravalency) and Rydberg transitions. Chemists who received their training in electronic spectroscopy in connection with the tr electron systems of aromatic molecules are usuaUy surprised when they are told about molecular Rydberg transitions. Yet, beyond 200 nm and armetimes even at loiter. wavelengths the existence of Rydberg bands is a fact of life. No spectrum can be interpreted without them. 

The oddities of the NMR method are most interesting. Firstly, there is negligible change in chemical shift of the resonances of the solute in many systems in which charge-transfer complexing is known to occur. Only with aromatic donor molecules have significant shifts been observed, and with such a system and F nuclei behave differently. Yet the same value of K within experimental error is obtained, whether donor, acceptor, or F resonances, or more than one resonance in the same species is employed. Further, these values of K agree with those obtained by electronic spectroscopy provided [D] = 2[A] in the latter determinations. 

Spectrometry Overview. Mercury. Microscopy Techniques Scanning Electron Microscopy X-Ray Microscopy. Particle Size Analysis. Polychlorinated Biphenyls. Polycyclic Aromatic Hydrocarbons Environmental Aj li-cations. Radiochemical Methods Overview. Sample Handling Sample Preservation. Sampling Theory. Surface Analysis Auger Electron Spectroscopy. Tin. X-Ray Absorption and Diffraction Overview. X-Ray Fluorescence and Emission Energy Dispersive X-Ray Ruores-cence Particle-Induced X-Ray Emission. 

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