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971.
A 23 factorial design has been used to analyze the effect of pH, the nature of the catalyst, and the concentration of the substrate
on the rate constant of the photodegradation reaction of phenol. The main effects of the considered variables and their interaction
are discussed. The significance of the effects has been corroborated using an ANOVA test. The values of phenol concentrations,
used to calculate the rate constant, and the concentrations of intermediates were obtained by applying parallel factor (PARAFAC)
analysis to the data obtained from monitoring the process by means of excitation–emission fluorescence (EEM). The proposed
methodology, which combines experimental design and multivariate techniques, is a rapid alternative for study of chemical
kinetics. 相似文献
972.
973.
974.
We study single dibenzoterrylene (DBT) molecules embedded in 1,4‐dichlorobenzene (para‐dichlorobenzene, pDCB) at 1.2 K. Due to the relatively low melting point of pDCB (53 °C), this host‐guest system can be easily prepared from the molten phase. Narrow linewidths, stable molecular lines and high saturation count rates of single DBT molecules were observed. For this reason, we consider this host‐guest system a promising candidate for the study of interactions of single molecules with other small objects such as waveguides or nanoparticles. 相似文献
975.
The use of laser radiation with tunable wavelength allows the selective excitation of actinide/lanthanide species with subsequent registration of luminescence/chemiluminescence for their detection. This work is devoted to applications of the time-resolved laser-induced luminescence spectroscopy and time-resolved laser-induced chemiluminescence spectroscopy for the detection of lanthanides and actinides. Results of the experiments on U, Eu, and Sm detection by TRLIF method in blood plasma and urine are presented. Data on luminol chemiluminescence in solutions containing Sm(III), U(IV), and Pu(IV) are analyzed. It is shown that appropriate selectivity of lanthanide/actinide detection can be reached when chemiluminescence is initiated by transitions within 4f- or 5f-electron shell of lanthanide/actinide ions corresponding to the visible spectral range. In this case chemiluminescence of chemiluminogen (luminol) arises when the ion of f element is excited by multi-quantum absorption of visible light. The multi-photon scheme of chemiluminescence excitation makes chemiluminescence not only a highly sensitive but also a highly selective tool for the detection of lanthanide/actinide species in solutions. 相似文献
976.
Chidthong R Hannongbua S Aquino AJ Wolschann P Lischka H 《Journal of computational chemistry》2007,28(10):1735-1742
The structural and electronic properties of the fluorene-pyridine copolymer (FPy)(n), (n = 1-4) were investigated theoretically by means of quantum mechanical calculations based on density functional theory (DFT) and time-dependent DFT (TD-DFT) using the B3LYP functional. Geometry optimizations of these oligomers were performed for the ground state and the lowest excited state. It was found that (FPy)(n) is nonplanar in its ground state, whereas a more pronounced trend toward planarity is observed in the S(1) state. Absorption and fluorescence energies have been extrapolated to infinite chain length making use of their good linearity with respect to 1/n. An extrapolated value of 2.64 eV is obtained for vertical excitation energy. The S(1)<--S(0) electronic excitation is characterized as a highest occupied molecular orbital to lowest unoccupied molecular orbital transition and is dominating in terms of oscillator strength. Fluorescence energies and radiative lifetime were calculated as well. The obtained results indicate that the fluorescence energy and radiative lifetime of (FPy)(n) are 2.16 eV and 0.38 ns, respectively. The decrease of fluorescence energy and radiative lifetime with the increase in the chain length is discussed. 相似文献
977.
Excitation Energy Transfer and Exchange-Mediated Quartet State Formation in Porphyrin-Trityl Systems
Oliver Nolden Nico Fleck Emmaline R. Lorenzo Prof. Michael R. Wasielewski Prof. Dr. Olav Schiemann Prof. Dr. Peter Gilch Dr. Sabine Richert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2683-2691
Photogenerated multi-spin systems hold great promise for a range of technological applications in various fields, including molecular spintronics and artificial photosynthesis. However, the further development of these applications, via targeted design of materials with specific magnetic properties, currently still suffers from a lack of understanding of the factors influencing the underlying excited state dynamics and mechanisms on a molecular level. In particular, systematic studies, making use of different techniques to obtain complementary information, are largely missing. This work investigates the photophysics and magnetic properties of a series of three covalently-linked porphyrin-trityl compounds, bridged by a phenyl spacer. By combining the results from femtosecond transient absorption and electron paramagnetic resonance spectroscopies, we determine the efficiencies of the competing excited state reaction pathways and characterise the magnetic properties of the individual spin states, formed by the interaction between the chromophore triplet and the stable radical. The differences observed for the three investigated compounds are rationalised in the context of available theoretical models and the implications of the results of this study for the design of a molecular system with an improved intersystem crossing efficiency are discussed. 相似文献
978.
针对常规超声反射系数对界面接触状态灵敏度受限问题,论文发展一种用于界面接触状态评价的超声信号相似度分析方法。针对不同压力下承压界面超声检测信号,研究了激励信号带宽、相似度函数类型及分析域对相似度分析方法对界面接触状态评价的影响。结果表明,检测信号的相似度指标随压力增加呈现明显规律性。激励信号带宽、相似度函数类型和分析域对界面接触状态评价效果有很大的影响。宽带激励下的时域欧式距离指标对界面压力微变化最为敏感,可用于界面接触状态的定量评价。 相似文献
979.
We study the entanglement dynamics of two atoms coupled to their own Jaynes-Cummings cavities in single-excitation space.Here,we use concurrence to measure atomic entanglement,and consider the Bell-like states to be initial states.Our analysis suggests that collapse and revival take place in entanglement dynamics.The physical mechanism behind entanglement dynamics is periodic information and energy exchange between atoms and light fields.For the initial Bell-like states,evolutionary periodicity of the atomic entanglement can only be found if the ratio of the two atom-cavity coupling strengths is a rational number.Also,whether there is a time translation between two kinds of initial Bel-like state depends on odd versus even numbers of the coupling strength ratio. 相似文献
980.
Nonlinear vibration of iced cable under wind excitation using three-degree-of-freedom model 下载免费PDF全文
《中国物理 B》2021,30(9):90503-090503
High-voltage transmission line possesses a typical suspended cable structure that produces ice in harsh weather. Moreover, transversely galloping will be excited due to the irregular structure resulting from the alternation of lift force and drag force. In this paper, the nonlinear dynamics and internal resonance of an iced cable under wind excitation are investigated.Considering the excitation caused by pulsed wind and the movement of the support, the nonlinear governing equations of motion of the iced cable are established using a three-degree-of-freedom model based on Hamilton's principle. By the Galerkin method, the partial differential equations are then discretized into ordinary differential equations. The method of multiple scales is then used to obtain the averaged equations of the iced cable, and the principal parametric resonance-1/2 subharmonic resonance and the 2:1 internal resonance are considered. The numerical simulations are performed to investigate the dynamic response of the iced cable. It is found that there exist periodic, multi-periodic, and chaotic motions of the iced cable subjected to wind excitation. 相似文献