On the theory of collision-induced vibrational transitions in polyatomic molecules: The mode-matching model

A modification of the SSH theory for collision-induced vibrational transitions in polyatomic molecules is proposed. The breathing-sphere model assumptions are avoided by considering the angular relation between the direction of approach and the normal modes displacements of the atoms involved in the contract (mode-matching). The results, as compared to the breathing-sphere model, indicate a considerable, mode specific reduction of the transition probabilities. Intramolecular transitions of CH₃Cl are studied as an example.     

Ab initio MRD-CI study of ethane: The 14–25 eV PES region and Rydberg states of positive ions

Ab initio calculations of the MRD-CI type are reported for various states of the C₂H₆⁺ ion in two different nuclear geometries and the results are compared with the experimentally observed ethane PES in the 14–25 eV region. The calculated vertical IP values for ionization out of the 1e_u, 2a_2u and 2a_1g MO's respectively agree well with the locations of the three ionization maxima in this spectral range. The analogous findings for excitation out of the relaxed ionic ground state find several relatively low-lying species which occupy a 2pσ* MO in addition to states resulting from simple ionization of the neutral molecule. A number of Rydberg states are also calculated at the relaxed-ion geometry, from which results it is determined that the quantum defects for such species are from 0.40–0.45 units smaller than for their counterparts in neutral systems; these findings are clearly consistent with a decrease in the core penetrability of the Rydberg electron as the effective charge is increased to Z = 2.     

Capillary electrophoretic separation of uncharged polymers using polyelectrolyte engines. Theoretical model

Fixed-size moving window evolving factor analysis and base peak chromatograms have been used for peak purity detection in data generated with LC-MS. The two methods were evaluated with both real and simulated data and were found to be fast and complementary to each other. When a possibly impure peak is detected, it is suggested that further information can be obtained from local principal component analysis modelling and comparative mass chromatogram plots.     

Anisotropic diffusion in a nematic liquid crystal- An electric field PFG NMR approach

The access to self-diffusion coefficients in anisotropic systems such as thermotropic liquid crystals by means of PFG NMR is complicated by strong dipolar interactions. Additionally, problems arise due to the immediate orientation of low-molar-mass nematic liquid crystals in an external field. The director orientation can be changed by the application of an additional electric field. This can be exploited in order to reduce the dipolar interaction to such an extent that the NMR linewidths change from a solid-state to a liquid-like situation enabling PFG NMR experiments.     

Synthese der γ-Amino-n-kapronsäure und des α′-Äthyl-α-pyrrolidons

Ohne Zusammenfassung     

Filmbildung aus Emulsionen,II

Ohne ZusammenfassungMitteilung Nr. 50.