Untersuchung von Wasser

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Untersuchung der Fette

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Synthesis,structural analysis,and self-assembly of phenylene ethynylene oligomers and their ?F, ?CF3, and ?CH3 substituted derivatives

Oligomers consisting of aromatic building blocks separated by alkynyl units were synthesized by Sonogashira cross-coupling of aryl halides with terminal acetylenes. Strong electron acceptors such as  F and  CF₃ and weak electron donors like  CH₃ were placed as substituents on one of the benzene rings. Acetyl-protected sulfhydryl groups were attached to one end of these molecules to promote their self-organization on gold surfaces. The electron-transport properties of such self-assembled monolayers (SAMs) are highly sensitive to the local order of the molecules in the solid state. Single crystals were analyzed by X-ray diffraction experiments that revealed structural details that could lead to a better understanding of the electron-transport properties. The unsymmetrical substitution of the aromatic rings by electron-active groups in the ortho-, meta-, or para positions resulted in changes of such molecular parameters as bonding and torsion angles and planarity. These parameters, in turn, can affect the angle of the molecular attachment to a gold substrate and the density of the resulting SAMs. Patterned SAMs of some of these molecules and comparison alkane thiols were obtained on gold by microcontact printing or flooding. The SAM thickness was determined by spectroscopic ellipsometry. Surface potential differences between adjacent SAMs or between SAMs and the gold substrate were measured by scanning surface potential microscopy under ambient conditions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 541–550, 2004     

Spectroscopic study of a representative polar cap of buckminsterfullerene: Cyclopentacorannulene

The spectroscopic properties of corannulene and cyclopentacorannulene are examined by use of absorption and steady-state fluorescence measurements. A red shift in the emission maxima of cyclopentacorannulene is noted with respect to the emission maxima in the corannulene spectrum. Similar differences in the absorption spectra of both molecules are also observed. Reasons for the dissimilarities in the absorption and emission spectra of these molecules are discussed. The fluorescence quantum yields and lifetimes of the molecules measured in organic solvents are reported. The fluorescence quantum yield and lifetime of cyclopentacorannulene are lower than those of corannulene. This difference is attributed to the highly strained and nonplanar structure of cyclopentacorannulene. The effectiveness of nitromethane as a quencher of corannulene and cyclopentacorannulene fluorescence is examined. In contrast to previously reported results, the fluorescence of these molecules is quenched by nitromethane. Fluorescence quenching of the molecules has been attributed to complex formation in the ground state, i.e., static quenching.     

On Anosov automorphisms of nilmanifolds

The only known examples of Anosov diffeomorphisms are hyperbolic automorphisms of infranilmanifolds, and the existence of such automorphisms is a really strong condition on the rational nilpotent Lie algebra determined by the lattice, so called an Anosov Lie algebra. We prove that n⊕?⊕n (s times, s≥2) has an Anosov rational form for any graded real nilpotent Lie algebra n having a rational form. We also obtain some obstructions for the types of nilpotent Lie algebras allowed, and use the fact that the eigenvalues of the automorphism are algebraic integers (even units) to show that the types (5,3) and (3,3,2) are not possible for Anosov Lie algebras.     

Oscillographische Bestimmung der auf Elektrodenoberfl?chen adsorbierten reduzierbaren und oxydierbaren Stoffe

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Remarkably volatile copper(II) complexes of N,N'-unsymmetrically substituted 1,3-diketimines as precursors for Cu metal deposition via CVD or ALD

To enhance the volatility of the copper precursor in the copper deposition process, it was envisioned that N,N'-unsymmetrically substituted 1,3-diketimines should be more volatile than their symmetrically substituted counterparts. A variety of Cu(II) (N,N'-unsymmetrically substituted 1,3-diketiminate) complexes have been synthesized and have proven to be much more volatile than their symmetrical counterparts. This makes the new materials particularly attractive to the ALD and CVD processes. Among the new compounds, 8-a and 8-b are sublimable even at room temperature.     

Proton-neutron excitations in the high-spin states of 95Tc

The high-spin states of ⁹⁵Tc have been studied in the reaction ⁹³Nb(α, 2n)⁹⁵Tc using inbeam spectroscopy of both γ-rays and conversion electrons. A new sequence of negative-parity states extending up to angular momentum $\text{I =}\text{29}\text{2}$ was found to exist within an excitation energy interval of 4.1 MeV. The positive-parity states are in remarkable agreement with the predictions of a simplified shell-model approach on the basis of coupled excitations of $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton and $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^{\mathrm{?}}$ as well as $\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ neutron configurations. A similar analysis for the negative-parity states shows qualitative agreement with the experimental results.     

Tunable detection of high-frequency phonons in LaF3

Tunable detection of high-frequency phonons in LaF₃ is reported. Phonons generated by a heat-pulse technique are detected by phonon-induced fluorescence from magnetically split energy levels of Er³⁺ impurity ions. Evidence for a strongly frequency-dependent lifetime of acoustic phonons at frequencies above 600 GHz is found. The lifetime is attributed to spontaneous anharmonic phonon decay.