Eine Erweiterung des Funktionalkalküls für lineare Operatoren

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Approximationssätze für Halbgruppen von Operatoren in topologischen Vektorräumen

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Two ammonium tetrachloridoaluminate salts: how a twinned orthorhombic structure emulates a trigonal crystal system

We have determined the crystal structures of two tetrachloridoaluminate salts. Tetrabutylammonium tetrachloridoaluminate benzene hemisolvate, (C₁₆H₃₆N)[AlCl₄]·0.5C₆H₆, (I), crystallizes with discrete cations, anions and solvent molecules. The benzene molecule is located on a centre of inversion. The structure of the benzene‐free polymorph has been determined previously. Tetraethylammonium tetrachloridoaluminate, (C₈H₂₀N)[AlCl₄], (II), also crystallizes with discrete cations and anions, and forms crystals which appear trigonal but are actually orthorhombic. With the additional reflections of the second and third domains of this nonmerohedral twin, a trigonal lattice is emulated, although the correct crystal system is orthorhombic.     

Optimal control of ultrafast laser driven many-electron dynamics in a polyatomic molecule: N-methyl-6-quinolone

We report time-dependent configuration interaction singles calculations for the ultrafast laser driven many-electron dynamics in a polyatomic molecule, N-methyl-6-quinolone. We employ optimal control theory to achieve a nearly state-selective excitation from the S(0) to the S(1) state, on a time scale of a few ( approximately 6) femtoseconds. The optimal control scheme is shown to correct for effects opposing a state-selective transition, such as multiphoton transitions and other, nonlinear phenomena, which are induced by the ultrashort and intense laser fields. In contrast, simple two-level pi pulses are not effective in state-selective excitations when very short pulses are used. Also, the dependence of multiphoton and nonlinear effects on the number of states included in the dynamical simulations is investigated.     

On the reactive uptake of gaseous compounds by organic-coated aqueous aerosols: theoretical analysis and application to the heterogeneous hydrolysis of N2O5

The presence of organic coatings on aerosols may have important consequences to the atmospheric chemistry, in particular to the N2O5 heterogeneous hydrolysis. This is demonstrated by recent experiments which show that the uptake of N2O5 by aqueous aerosols is slowed considerably when an organic coating consisting of monoterpene oxidation products is added on the particles. To treat the mechanisms behind the suppression, an extension of the resistor model, which has been widely applied in investigation of the heterogeneous uptake by aerosols, was derived. The extension accounts for dissolution, diffusion, and chemical reactions in a multilayered organic coating, and it provides a parametrization for the heterogeneous uptake by organic-coated aerosols that can be applied in large-scale models. Moreover, the framework was applied to interpret the findings regarding the decreased uptake of N2O5 by the organic-coated aerosols. Performed calculations suggested that the reaction rate constant of N2O5 in the coating is decreased by 3-5 orders of magnitude, in addition to which the product of the solubility of N2O5 and its diffusion coefficient in the coating is reduced more than an order of magnitude compared to the corresponding value for the aqueous phase. The results suggest also that the accommodation coefficient of N2O5 to such coatings is no more than a factor of 2 smaller than that to pure water surfaces. Finally, the relevance of the results to the atmospheric N2O5 heterogeneous hydrolysis is discussed and implications to planning further laboratory studies focusing on secondary organic aerosol formation are pointed out.     

The homotopy type of the cobordism category

The embedded cobordism category under study in this paper generalizes the category of conformal surfaces, introduced by G. Segal in [S2] in order to formalize the concept of field theories. Our main result identifies the homotopy type of the classifying space of the embedded d-dimensional cobordism category for all d. For d = 2, our results lead to a new proof of the generalized Mumford conjecture, somewhat different in spirit from the original one, presented in [MW].     

Distributionen als Randverteilungen analytischer Funktionen. II

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Blue amplified spontaneous emission from a stilbenoid-compound-doped polymer optical fiber

We report on the fabrication and characteristics of a step-index glass-clad polymer optical fiber that uses a novel fluorescent stilbenoid compound for lasing and amplification applications. The compound, 1, 4-bis(4-diphenyl-amino-styryl)-benzene, is specifically designed for the blue region of the spectrum and has a very high quantum yield of 0.85 in a solid-state polymer host and a large Stokes shift. Significant spectral narrowing and superlinear increase of output intensity are observed under photoexcitation at 355 nm, which are indicative of the occurrence of amplified spontaneous emission. By means of gain spectroscopy, a large optical gain of up to 36 cm(-1) at 494 nm has been obtained for the fiber when it is transversely photoexcited at 12 mJ/cm(2) . The waveguide loss has been measured to be 0.7 cm(-1) at 494 nm. The demonstration of high gain and low waveguide loss has favorable implications for the construction of a very compact, tunable coherent light source.