基态原子与理想金属Au表面间的范德瓦尔斯作用

研究了基态碱金属原子与理想金属Au表面间的范德瓦尔斯(vdW)作用.通过分析电四极跃迁对vdW的贡献,构建了计算超精细能级碱金属原子与理想金属表面间vdW作用系数C3的理论模型.以85Rb、133Cs为例,计算了其基态原子超精细能级的C3系数.其中85Rb: 52S1/2 (F=2)及52S1/2 (F=3)对应的C3系数分别为:2.2409 及2.2425 ;133Cs: 62S1/2 (F=3)及62S1/2 (F=4)分别对应 2.4480 及2.4538 .研究还发现随着 的增大,C3增大,z (原子与金属表面之间的距离)不变时,原子与理想金属表面间vdW作用增强. 这一研究在实现原子囚禁及介质表面量子反射等方面具有重要意义     

Trajectory approach to the Schrödinger–Langevin equation with linear dissipation for ground states

The Schrödinger–Langevin equation with linear dissipation is integrated by propagating an ensemble of Bohmian trajectories for the ground state of quantum systems. Substituting the wave function expressed in terms of the complex action into the Schrödinger–Langevin equation yields the complex quantum Hamilton–Jacobi equation with linear dissipation. We transform this equation into the arbitrary Lagrangian–Eulerian version with the grid velocity matching the flow velocity of the probability fluid. The resulting equation is simultaneously integrated with the trajectory guidance equation. Then, the computational method is applied to the harmonic oscillator, the double well potential, and the ground vibrational state of methyl iodide. The excellent agreement between the computational and the exact results for the ground state energies and wave functions shows that this study provides a synthetic trajectory approach to the ground state of quantum systems.     

Evaluation and Optimization of the Oxidation efficiency of a UV-Persulphate-Oxidation Toc-Analyzer for the Determination of Oil Contamination from Forestry in Ground Water

Different chain oils (tall, rape seed and mineral oils) have been used as model compounds to evaluate and optimize the applicability of UV-persulphate TOC-analyzer for quantitative determination of forestry oils and to follow the progress of their biodegradability. It was shown, that K 2 S 2 O 8 -UV-oxidation method is not sufficient to oxidize chain oils completely. There were differences in oxidation efficiency between different oils, changing from about 46% measured for tall oil to about 25% observed for rape seed chain oil. The addition of Triton X-100 surfactant up to 2% (w/w) was observed to increase the oxidation efficiency, e.g. to 75% for tall oil. The observations can be explained by assuming that in the presence of surfactant the emulsions are more homogeneous and stable. Optimization using two-level full factorial design (temperature of the oxidation chamber and the amount of persulphate) was studied. The results show that the UV-persulphate-oxidation TOC-analyzer is not suitable method to monitor biodegradability of chain oils.     

Bichromophoric hemicyanine dyes as fluorescence probes applied for monitoring of the photochemically initiated polymerization

The spectroscopic properties of series homodimmeric hemicyanine dyes based on (p-N,N-dimethylaminostyryl)benzothiazolium, (p-N,N-dimethylaminostyryl)benzoxazolium, (p-N,N-dimethylaminostyryl)-2,3,3-trimethyl-3H-indolium residues were determined. The absorption and fluorescence spectra of the dyes under study were measured in different polarity solvents at room temperature. On the basis of the solvatochromic behavior the ground state (μ_g) and excited state (μ_e) dipole moments of bis-(N,N-dimethylaminostyryl) derivatives were evaluated. The dipole moments (μ_g and μ_e) were estimated from solvatochromic shifts of absorption and fluorescence spectra as function of dielectric constant (ε) and refractive index (n) of applied solvents. The absorption and fluorescence spectra are only slightly affected by the solvent polarity. The analysis of solvatochromic behavior of the fluorescence spectra as a function of Δf (ε, n) revealed that the emission occurs from a high polarity excited state. The large dipole moment changes along with the red-shifted fluorescence, as the solvent polarity is increased, demonstrates the formation of an intramolecular charge transfer state (ICT). Six bichromophoric hemicyanine dyes, possessing benzothiazole, benzoxazole or indolinium group linked by 5 or 10 methylene groups were evaluated as fluorescence probes applied for monitoring of the polymerization process. The study on the changes in fluorescence intensity and spectroscopic shift of studied compounds were carried out during photochemically initiated polymerization of 2-ethyl-2-(hydroxymethyl)-propane-1,3-diol triacrylate (TMPTA).     

Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure

Missing VO₂(A) usually occurs during the preparation of VO₂ polymorphs. This leads to an ambiguous understanding of the transformation between VO₂ polymorphs. The calculation of the ground state energies for different VO₂ polymorphs indicated that there is only a small energy gap between VO₂(A) and VO₂(R), which destined that the transformation from VO₂(A) to VO₂(R) should be pressure sensitive. This hypothesis was verified during the synthesizing of VO₂ polymorphs by reducing V₂O₅ with oxalic acid through hydrothermal treatment process. Selective formation of pure phase VO₂(A) or VO₂(R) was achieved by controlling the hydrothermal pressure through varying the filling ratio at 270 °C. It was found that a filling ratio over 0.5 favors the formation of pure VO₂(R) while a reduced filling ratio to 0.4 or lower results in the formation of VO₂(A). Based on our experiments, VO₂(B) nanobelts were always first formed and then it transformed to VO₂(A) by assembling process at increased temperature or extended reaction time. Under further higher pressure, the VO₂(A) transformed spontaneously to VO₂(R) initialized from the volume shrinkage due to the formation of denser VO₂(R).     

Aspect-Ratio Scaling of Domain Wall Entropy for the 2D ±<Emphasis Type="Italic">J</Emphasis> Ising Spin Glass

The ground state entropy of the 2D Ising spin glass with +1 and −1 bonds is studied for L×M square lattices with L≤M and p=0.5, where p is the fraction of negative bonds, using periodic and/or antiperiodic boundary conditions. From this we obtain the domain wall entropy as a function of L and M. It is found that for domain walls which run in the short, L direction, there are finite-size scaling functions which depend on the ratio , where d _S =1.22±0.01. When M is larger than L, very different scaling forms are found for odd L and even L. For the zero-energy domain walls, which occur when L is even, the probability distribution of domain wall entropy becomes highly singular, and apparently multifractal, as becomes large.     

以喹啉衍生物和乙酰丙酮为配体的Ir配合物的结构和光谱性质的理论研究

用密度泛函理论(DFT)B3LYP方法对以喹啉衍生物(C∧N)及乙酰丙酮(acac)为配体的金属Ir(Ⅲ)的三个配合物的电子结构和光谱性质进行了理论研究. 计算结果表明, 当喹啉上的取代基(sub)由苯变为联苯或萘时, 电离能变小, 电子亲和势变大, 尤其是分子3, 可预测其能作为电子传输材料和空穴传输材料. 同时, HOMO和 LUMO之间的能隙变窄, 导致光谱红移. T1态主要为HOMO→LUMO 的跃迁. T1→S0 的磷光发射过程为MLCT和LLCT的混合.