Amino-acyl-quinoxalinone yellow dyes are cyclised analogues of the yellow azomethine dyes developed for, and still used in, silver halide colour photography. Unlike image azomethine dyes, which are rapidly deactivated in their excited states by torsion about the azomethine bond, amino-acyl-quinoxalinone dyes have an interesting photophysics because torsion is not possible due to their cyclised structure. We report results from studies on singlet and triplet state properties, and singlet oxygen yields, of the yellow dye, 7-diethylamino-3-(2,2-dimethyl-propionyl)-5-methyl-1-phenyl-1H-quinoxalin-2-one, in polar and nonpolar solvents. The dye photophysics is characterised by a weak fluorescence, with a solvent dependent emission yield (ΦF?≈?0.002–0.004), and short singlet state lifetime (τexpt?≈?20–50 ps), both increasing by a factor of ≈2 in going from polar acetonitrile to non-polar dioxane as solvent. DFT ZINDO calculations show a transition involving significant electron transfer from the diethyl-amino group into the carbonyl region of the molecule. In solution, in the presence of oxygen, the triplet state decays almost exclusively by oxygen quenching, and singlet oxygen is produced in high yield (Φ??≈?0.5–0.55). The triplet state absorbs across the 450–750 nm region with maxima around 480 and 650 nm, and moderate molar absorption coefficients (ca. 6000–8000 M?1 cm?1). In a glass at 77 K, triplet decay gives a red phosphorescence, with λmax?≈?640–650 nm, and a ?≈?0.25 s lifetime. If singlet oxygen yields are a good indication of triplet yields, then internal conversion and intersystem crossing occur with roughly equal efficiency.
Aequationes mathematicae - In this paper, we establish a new class of dynamic inequalities of Hardy’s type which generalize and improve some recent results given in the literature. More... 相似文献
Adapting hydrogen as a carbon-free fuel for industrial applications requires new, innovative approaches, especially when radiant heat transfer is required. One possible option is to dope hydrogen with bio-oils, containing aromatics that help produce highly sooting flames. This study investigates the potential doping effects of toluene on a hydrogen-nitrogen (1:1 vol) flames. Flames with 1–5% toluene, based on the mole concentration of hydrogen, are measured using a combination of techniques including: still photographs and laser-based techniques. Toluene was mixed with hydrogen-nitrogen fuel mixture as either a vapour carried by nitrogen, or as a dilute spray. Spray flames are found to produce substantially more polycylic aromatic hydrocarbons, with significantly more soot near the nozzle exit plane, than the prevaporised flames. Increasing the dopant concentration from 1 to 3% of the hydrogen has a marked effect on soot loading in the flame, although the further increasing the dopant concentration to 5% has a far smaller effect on the soot produced in the flame. Simulations of laminar flames using detailed chemical kinetics support the above findings and reveal details of the competition between soot precursor formation and hydrocarbon oxidation. Correlations of formation rates are non-linear with toluene concentration in cases where toluene represents less than 10% of the fuel, although expected linear relationships are noted beyond this regime up to 1:1 toluene/hydrogen blends. The study provides insight and explanation into effects of toluene as a dopant, comparison between flame doping in gaseous or liquid phases and suggests that flame doping and blending should be treated as different regimes for their global effect on flame sooting characteristics. 相似文献
The interaction of solitary waves with multiple, in-line vertical cylinders is investigated. The fixed cylinders are of constant circular cross section and extend from the seafloor to the free surface. In general, there are N of them lined in a row parallel to the incoming wave direction. Both the nonlinear, generalized Boussinesq and the Green–Naghdi shallow-water wave equations are used. A boundary-fitted curvilinear coordinate system is employed to facilitate the use of the finite-difference method on curved boundaries. The governing equations and boundary conditions are transformed from the physical plane onto the computational plane. These equations are then solved in time on the computational plane that contains a uniform grid and by use of the successive over-relaxation method and a second-order finite-difference method to determine the horizontal force and overturning moment on the cylinders. Resulting solitary wave forces from the nonlinear Green–Naghdi and the Boussinesq equations are presented, and the forces are compared with the experimental data when available. 相似文献
Following a recent investigation on the N(2D) + H2O reaction [Homayoon et al., J. Phys. Chem. Lett. 5, 3508 (2014)], we report on an experimental and theoretical study of the isotopologue N(2D) + D2O reaction. Crossed molecular beam (CMB) experiments were conducted at a collision energy of 10.3 kcal mol–1. Quasiclassical trajectory calculations were performed on a recent potential energy surface to derive the centre-of-mass functions necessary to simulate the CMB laboratory distributions. Excellent agreement was found. The importance of the channel leading to HON/DON was confirmed. The inclusion of this channel, in addition to that leading to the isomer HNO/DNO, can affect the models considering the coupling between nitrogen and oxygen chemistry in the upper atmosphere of Titan. 相似文献