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51.
In this work, the geometrical structures, the formation energies, and electronic states of the Na(ms)Arn polyatomic exciplexes with m = 3-6 and n = 2-5 are studied by using a quantum-classical method. The interaction potential between an electronically excited sodium atom and argon atoms are calculated by using a one-electron model involving electron-Ar and electron-Na+ pseudopotentials, in which the Hamiltonian is diagonalized at every optimization step in the Basin Hopping algorithm. The relationship between the position of the electronically excited levels and the cluster geometry is investigated as a function of the excitation level and of the spatial extension of the excited electron orbital. We show that the equilibrium structures of the ground state Na(3s)Arn and those of the electronically excited states Na(4s)Arn, Na(5s)Arn, and Na(6s)Arn are significantly different. As a result of the detailed examination of the relationships between the geometrical structure and density distribution of the Na valence electron of the Na∗Arn with n = 2-5 polyatomic exciplexes, we can see that for the Na(4s)Arn polyatomic exciplexes, the two extreme geometries, neutral Na(3s)Arn and ionic Na+Arn compete. It appears that none of them is the actual one. For Na(5s)Arn and Na(6s)Arn the valence electron is very weakly bound to the ionic core and described by a more diffused orbital so that the geometry and the formation energies of this excited state called Rydberg states converge towards those of the ionic cores. 相似文献
52.
The characteristics of large coherent structures in turbulent, periodically-excited, as well as naturally-developing bubbly jets are investigated, and interactions between bubbles and large-scale vortices are studied quantitatively. 相似文献
53.
Anneli Kruve Riin Rebane Karin Kipper Maarja-Liisa Oldekop Hanno Evard Koit Herodes Pekka Ravio Ivo Leito 《Analytica chimica acta》2015
This is the part I of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS/MS) detection in LC (as opposed to the “conventional” detectors). The Part I briefly introduces the principles of operation of LC–MS (emphasizing the aspects important from the validation point of view, in particular the ionization process and ionization suppression/enhancement); reviews the main validation guideline documents and discusses in detail the following performance parameters: selectivity/specificity/identity, ruggedness/robustness, limit of detection, limit of quantification, decision limit and detection capability. With every method performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to determine it, specifically in the case of LC–MS methods. 相似文献
54.
硫代嘧啶碱基是光动力疗法潜在的重要光敏剂,其最低单重激发态的光物理研究已有广泛报道。然而,其较高激发态的跃迁性质和反应动力学研究较为稀少。因此,本文采用共振拉曼光谱和密度泛函理论计算方法研究2,4-二硫代尿嘧啶的紫外光谱和几个较高单重激发态的短时结构动力学。首先,基于共振拉曼光谱强度与电子吸收带振子强度f的关系,将紫外光谱去卷积成四个吸收带,分别为358 nm(f=0.0336)中等强度吸收带(A带),338 nm(f=0.1491)、301 nm(f=0.1795)和278 nm(f=0.3532)强而宽的吸收带(B、C和D带)。这一结果既吻合密度泛函理论计算结果,又符合共振拉曼光谱强度模式对紫外光谱带的预期。据此,去卷积得到的四个吸收带被分别指认为S0→S2跃迁、S0→S6跃迁、S0→S7跃迁和S_0→S_8跃迁。同时,分别对B,C和D带共振拉曼光谱进行了详细的指认,获得了短时动力学信息。结果表明,S_8态短时动力学的显著特征是在Franck-Condon区域或附近发生了S8(ππ~*)/S(nπ~*)势能面交叉引发的、伴随超快结构扭转的非绝热过程。S7和S6态短时动力学的主要特征是反应坐标的多维性,它们分别沿C_5C_6/C_2S_8/C_4S_(10)/N_2C_3+C_4N_3H_9/N_1C_2N_3/C_2N_1C_6/C_6N_1H_7/C_5C_6H_(12)和C_5C_6/N_3C_2/C_4S_(10)/C_2S_8+C_6N_1H_7/C_5C_6H_(12)/C_5C_6N_1/C_5C_6H_(12)/C_2N_1C_6/N_1C_2N_3/C_4N_3H_9/N_1C_2N_3等内坐标演化。 相似文献
55.
使用密度泛函理论(DFT)B3LYP/6-31G(d)方法优化得到了3(5)-(9-蒽基)吡唑及其衍生物的基态(S0)分子结构, 使用单激发组态相互作用(CIS)/6-31G(d)方法优化得到这些分子的第一单重激发态(S1)的几何结构, 并使用含时密度泛函理论(TD-DFT)B3LYP/6-311++G(d,p)方法计算了它们的吸收和发射光谱. 计算结果表明, 与3(5)-(9-蒽基)吡唑相比, 无论取代基是吸电子基团还是供电子基团, 衍生物的吸收和发射峰均发生红移, 并且当取代基―R=―BH2, ―CCl3, ―CHO, ―NH2时衍生物有较长的吸收波长和发射波长. 相似文献
56.
Liu Y Yang D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):213-218
The combined density functional theory (DFT) and time-dependent density functional theory (TDDFT) method was used to study the electronic spectral properties of different deprotonated forms of esculetin. By comparing the experimental absorption and fluorescence bands with the calculated electronic spectra, it is evidently demonstrated that the minor absorption and fluorescence bands observed at slightly longer wavelengths than the principal bands in experiments are predominantly from the de-H3 form of the esculetin monomer. Furthermore, we clarified the relationship between electronic spectral shifts and electronic excited-state intramolecular hydrogen bonding changes: the strengthening of intramolecular hydrogen bond can induce an electronic spectral blueshift while the intramolecular hydrogen bond weakening can result in an electronic spectral redshift. 相似文献
57.
In a recent paper, Nguyen et al. (2018) built a distributionally robust estimator for the precision matrix of the Gaussian distribution. The distributional uncertainty size is a key ingredient in the construction of this estimator. We develop a statistical theory which shows how to optimally choose the uncertainty size to minimize the associated Stein loss. Surprisingly, rather than the expected canonical square-root scaling rate, the optimal uncertainty size scales linearly with the sample size. 相似文献
58.
The CASPT2 calculations for the S0, T1, S1, T2, and S2 states of the cis- and trans-CH3ONO molecules predict the energy levels and geometries of the cis- and trans-isomers in the different states. The CASPT2 adiabatic (T 0) and vertical (T v) excitation energies are in good agreement with available experimental data (for the S1 cis- and trans-isomers). The CH3O-NO dissociation potential energy curves were calculated at the CASPT2//CASSCF level, and the CASPT2 calculations were performed for the transition states along the T1, S1, and T2 dissociation paths. For the repulsive S2 state the calculations predict the T v values larger than 5.4 eV and dissociation products of CH3O (12A″) + NO (X2Π). 相似文献
59.
60.
Cs蒸气中的碰撞能量合并和6P3/2和6P1/2间的激发转移 总被引:2,自引:0,他引:2
通过激发转移和碰撞能量合并研究了Cs(62P)精细结构混合.单模半导体激光器激发基态Cs原子至6P3/2态,直接荧光是由6P3/2态发射的,敏化荧光是由精细结构碰撞转移和碰撞能量合并产生的.由相对荧光强度得到了转移截面σ(6P3/2→6P1/2)=(1.5±0.5)×10-15cm2,与其它实验结果进行了比较. 相似文献