Theoretical investigations on absorption and fluorescence of perylene and its tetracarboxylic derivatives

Summary Theoretical molecular geometries of the perylene derivatives 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA), 3,4,9,10-perylene tetracarboxylic diimide (PTCDI), N,N-dimethyl 3,4,9,10-perylene tetracarboxylic diimide (MePTCDI), and 3,4,9,10-perylene tetracarboxylic disulfide (PTCDS) are presented for the electronic statesS ₀ andS ₁. On this basis, the electronic absorption properties can be interpreted and compared with experimentel data. The vibronic structure ofS ₀ S ₁ absorption andS ₁ S ₀ fluorescence has been reproduced. The analysis of the active vibrational modes shows a corresponding behaviour of derivatives and perylene.

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Theoretische Untersuchungen der Absorption und Fluoreszenz von Perylen und seinen Tetracarbonsäure-Derivaten

Zusammenfassung Theoretische Molekülgeometrien der Perylen-Derivate 3,4,9,10-Perylentetracarbonsäuredianhydrid (PTCDA), 3,4,9,10-Perylentetracarbonsäurediimid (PTCDI), N,N-Dimethyl-3,4,9,10-Perylentetracarbonsäurediimid (MePTCDI) und 3,4,9,10-Perylentetracarbonsäuredisulfid (PTCDS) für die elektronischen ZuständeS ₀ undS ₁ werden vorgestellt. Auf dieser Grundlage können die elektronischen Absorptionseigenschaften interpretiert und mit experimentellen Daten verglichen werden. Die vibronische Struktur derS ₀ S ₁-Absorption und derS ₁ S ₂-Fluoreszenz konnte reproduziert werden. Die Analyse der aktiven Schwingungsmoden zeigen ein gegenüber Perylen vergleichbares Verhalten der Derivate.

     

Juncunol : Revision of structure and synthesis

Synthetic studies have shown that juncunol is 2-hydroxy-1,7-dimethyl-5-vinyl-9,10-dihydrophenanthrene $\text{18}$, and not the 1,6-dimethyl-7-vinyl isomer $\text{2}$ as originally assumed.     

Duality relations for asymmetric exclusion processes

We derive duality relations for a class ofU _q [SU(2)]-symmetric stochastic processes, including among others the asymmetric exclusion process in one dimension. Like the known duality relations for symmetric hopping processes, these relations express certainm-point correlation functions inN-particle systems (Nm) in terms of sums of correlation functions of the same system but with onlym particles. For the totally asymmetric case we obtain exact expressions for some boundary density correlation functions. The dynamical exponent for these correlators isz=2, which is different from the dynamical exponent for bulk density correlations, which is known to bez=3/2.     

Blank values, adsorption, pre-concentration, and sample preservation for arsenic speciation of environmental water samples

Arsenic is the focus of public attention because of its toxicity. Arsenic analysis, its toxicity, and its fate in the environment have been broadly studied, still its blank values, adsorption to sampling materials and pre-concentration of water samples as well as stabilization of arsenic compounds in water samples under field conditions have been very little investigated. In this study, we investigate the blank values and adsorption of arsenic compounds for different laboratory materials. We focused our work onto pre-concentration of water samples and how to stabilize arsenic compounds under field conditions. When using glassware for arsenic analysis, we suggest testing arsenic blank values due to the potential release of arsenic from the glass. Adsorption of arsenic compounds on different laboratory materials (<10%) showed little influence on the arsenic speciation. Pre-concentration of methanol-water solutions could result in potential overestimation of arsenic compounds concentrations. Successful pre-concentration of water samples by nitrogen-purge provides an analytical possibility for arsenic compounds with high recoveries (>80%) and low transformation of arsenic compounds. Thus, concentrations as low as 1 ng As l⁻¹ can be determined. Addition of ethylenediaminetetraacetic acid (EDTA) and storage in the dark can decrease the transformation among arsenic compounds in rainwater and soil-pore water for at least a week under field conditions.     

Topometry for locally changing materials

Three-dimensional topometry is supplemented with ellipsometric measurements on the same pixel raster for calculation of the phase of the reflected waves and correction of the height fields. Lateral resolution is <1mum . The ellipsometric angles are determined by phase shifting and contrast evaluation. Three-dimensional fields of the ellipsometric angles, the real and the imaginary parts of the refractive index, and the corrected topography of the heights are presented.     

Reaction-diffusion processes of hard-core particles

We study a 12-parameter stochastic process involving particles with two-site interaction and hard-core repulsion on ad-dimensional lattice. In this model, which includes the asymmetric exclusion process, contact processes, and other processes, the stochastic variables are particle occupation numbers taking valuesn _x=0,1. We show that on a ten-parameter submanifold thek-point equal-time correlation functions n _x1...n _xk satisfy linear differential-difference equations involving no higher correlators. In particular, the average density n _x satisfies an integrable diffusion-type equation. These properties are explained in terms of dual processes and various duality relations are derived. By defining the time evolution of the stochastic process in terms of a quantum HamiltonianH, the model becomes equivalent to a lattice model in thermal equilibrium ind+1 dimensions. We show that the spectrum ofH is identical to the spectrum of the quantum Hamiltonian of ad-dimensional anisotropic, spin-1/2 Heisenberg model. In one dimension our results hint at some new algebraic structure behind the integrability of the system.     

Recent progress on contactless inductive flow tomography

The contactless inductive flow tomography (CIFT) is a technique to reconstruct the velocity in electrically conducting melts using magnetic fields. One of its application could be the velocity reconstruction in the mould of the continuous casting process. In this paper, we present the numerical investigation and first measurements of the induced magnetic field taken in our lab on a small model of a continuous casting mould. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation into the photo-induced change in wettability of hydrophobized TiO2 films

The photo-induced change in wettability of hydrophobized TiO₂ films has been investigated for steel coated with acidic TiO₂ nanosols containing varying concentrations of dispersed nanocrystalline titania, such as Degussa P25. The photo-induced change in wettability was evaluated by measuring the time-dependent drop of water contact angle (WCA) after samples had been soaked in either n-octyltriethoxysilane (OTS) or decanoic acid (DA). TiO₂ films treated in this way exhibit superhydrophobic behaviour, with WCA greater than 160°. After radiation with UV (black light), the superhydrophobic properties are transformed into superhydrophilic properties, with WCA of almost 0°. As P25 content and layer thickness increase, high rates of photo-induced change are found, but a moderate calcination regime is required. On the other hand, hardness and E modulus pass through a maximum at 25 wt% P25, so that a P25 content between 25 and 50 wt% is the optimum for practical uses. With such stable coatings, wettability can be controlled over a wide range, and the switch between hydrophobic and hydrophilic states can be carried out repeatedly when DA is used as the hydrophobizing agent. Use of a low calcination temperature (450 °C) for the intermediate annealing of the single layers in multilayer coatings and a short final sintering step at a relatively high temperature (e.g. 630 °C for 10 min) allow the preparation of relatively thin TiO₂ films on steel with a high photoactivity.     

Questioning the Recent Observation of Quantum Hawking Radiation

A recent article [J. Steinhauer, Nat. Phys. 2016 , 12, 959] has reported the observation of quantum Hawking radiation and its entanglement in an analogue black hole. Here, the published evidence, its consistency with theoretical bounds, and the statistical significance of the results are analyzed. The analysis raises severe doubts on the observation of Hawking radiation.