Quantum transport from the perspective of quantum open systems

By viewing the non-equilibrium transport setup as a quantum open system, we propose a reduced-density-matrix based quantum transport formalism. At the level of self-consistent Born approximation, it can precisely account for the correlation between tunneling and the system internal many-body interaction, leading to certain novel behavior such as the non-equilibrium Kondo effect. It also opens a new way to construct time-dependent density functional theory for transport through large-scale complex systems.     

Density functional study of the l-proline-catalyzed α-aminoxylation of aldehydes reaction: The reaction mechanism and selectivity

The reaction mechanism of the l-proline-catalyzed α-aminoxylation reaction between aldehyde and nitrosobenzene has been investigated using density functional theory (DFT) calculation. Our calculation results reveal following conclusions [1]. The first step that corresponds to the formation of C–O bond, is the stereocontrolling and rate-determining step [2]. Among four reaction channels, the syn-attack reaction channel is more favorable than that of the anti one, and the TS-ss channel dominates among the four channels for this reaction in the step of C–O bond formation [3]. The intermolecular hydrogen bond between the acidic hydrogen of l-proline and the N atom of the nitrosobenzene in an early stage of the process catalyzes very effectively the C–O bond formation by a large stabilization of the negative charge that is developing at the O atom along the electrophilic attack [4]. The effect of solvent decreases the activation energy, and also, the calculated energy barriers are decrease with the enhancement of dielectric constants for C–O bond formation step. These results are in good agreement with experiment, and allow us to explain the origin of the catalysis and stereoselectivity for l-proline-catalyzed α-aminoxylation of aldehyde reaction. The addition of H₂O to substituted imine proline, intermolecular proton-transfer steps, and the l-proline elimination process were also studied in this paper.     

Mass resolved MPI spectra of methyl iodide in the 430-490 nm region

The mass resolved multiphoton ionization (MPI) spectra of methyl iodide were obtained in the 430-490 nm region using a time-of-flight (TOF) mass spectrometer. They have the same vibrational structure, which testifies that the fragment species, in the wavelength region under study, are from the photodissociation of multiphoton ionized molecular parent ions. Some features in the spectra are identified as three-photon excitations to 6p and 7s Rydberg states of methyl iodide. Two new vibrational structures of some Rydberg states are observed. The mechanism of ionization and dissociation is also discussed.     

Crystal structure of Ni(NCS)2 · 2Ph3P

Crystals of the complex Ni(NCS)₂ · 2Ph₃P are triclinic with a = 7.939(4) Å, b = 10.457(5) Å, c = 11.474(5) Å, α = 111.08(3)°, β = 74.56(3)° and γ = 92.25(3)°. X-ray data for 2692 independent observed reflections were collected and the structure determined by Fourier methods and refined to R = 0.038. The nickel geometry is square planar with the triphenylphosphine ligands occupying trans positions. A feature of the structure is the large value (173.3°) for the NiNC angles.     

Reactive resonances in the photodissociation of symmetric triatomic molecules: an interpretation of collinear CO2 in terms of polar coordinates

We discuss the origin of reactive scattering resonances in absorption cross sections following the collinear photodissociation of symmetric triatomic molecules. The analysis of spectra for CO₂ dissociation, previously calculated by Kulander and Light, becomes very simple in terms of polar coordinates. Of particular interest is a symmetry effect which is not observable in ordinary scattering calculations.     

A coupled states reactive scattering study of bending excited resonances in three-dimensional H + H2

Reaction probabilities from coupled states calculations on the Liu-Siegbahn-Truhlar-Horowitz surface for H+H₂ are calculated for the energy range 0.90–1.30 eV. Peaks in the vibrationally inelastic reaction probabilities near 1.10, 1.20 and 1.22–1.24 eV suggest that bending excited resonances labelled by the quantum numbers (11¹0), (12⁰0) and (12²0) exist.     

Ground and excited state prototropic reactions in 2-(o-hydroxyphenyl)benzimidazole

A solvent dependence study of the steady state absorption, excitation and fluorescence spectra of 2-(o-hydroxyphenyl) benzimidazole has indicated the presence of different tautomers in the S₁ state which have the same precursor in the S₀ state. A similar study as a function of hydrogen ion concentration has identified the presence of dication, monocation, zwitterion, phototautomer and monoanion species. The respective pK_a and pK^*_a values have been determined with fluorimetric titrations and Förster cycle methods and compared.     

Structural and Bonding Properties of AlnC4-/0 (n=2-4) Clusters:Anion Photoelectron Spectroscopy and Theoretical Calculations

We measured the photoelectron spectra of AlnC4-(n=2-4) clusters by using size-selected anion photoelectron spectroscopy.The structures of AlnC4-/0 (n=2-4) clust...     

H+CH→H2+C（1D）反应的立体动力学研究

利用从头计算的对称性为1A′的势能面,用准经典轨线（QCT）方法在不同的碰撞能下研究了反应H+CH→H₂+C（¹D）的产物和反应物的矢量相关性质.在质心系下计算了四个极化微分反应截面.计算并讨论了描述k和j′夹角分布关系的P（θ_r）和描述k-k′-j′三者的二面角分布关系的P（（?）_r）.计算结果表明势能面上的深势阱和不同的碰撞能对产物分子H₂有重要影响.