Results 1 - 10 of 33
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[en] Highlights: • The stereodynamics of the S(3P) + H2 → SH + H reaction are firstly studied employing Quasi-classical trajectory method. • The distribution functions DCS, P(θr),P(ϕr) and P(θr,ϕr) are presented. • The influences of collision energy on the stereodynamics of the title reaction are investigated in detail. • The title reaction is dominated by the direct reaction mechanism. - Abstract: Quasi-classical trajectory calculations are firstly employed to study the stereodynamics of the title reaction on the lowest triplet state (3A″) potential energy surface constructed by Lv et al. (2012) . The calculated reaction probabilities and cross sections are in good agreement with the previous quantum mechanics results. The effects of collision energy on the vector properties including the k–k′ distribution and product polarization are investigated for the v = 0 and j = 0 states of H2 at Ecol = 1.2, 1.4, 1.8 and 2.2 eV. The calculated results indicate that the collision energy plays an important role in the stereodynamics of the title reaction
[en] The stereodynamics of the atom-molecule reactions H/D/T + LiH→HH/HD/HT + Li have been studied by means of the quasi-classical trajectory method, using the potential energy surface [Chem. Phys. Lett. 474, 18 (2009)] of Prudente et al. The cross section is calculated for various collision energies, and differential cross sections (DCSs), P(θr), P((φr), P(θr,φr) are presented at the collision energy of 0.25 eV. The results indicate that the cross section decreases with the increasing collision energy and the mass of the attacking atom. For the selected collision energy, the tendency of forward scattering is enhanced and backward scattering almost remains unchanged while the mass of the attacking atom increases, and the degree of alignment of product rotational angular momentum j' is enhanced, as well as oriented along the negative direction of the γ-axis. (authors)
[en] Using Lie-algebraic techniques and the simpler expressions of the matrix elements of Majorana operators given by us, we obtain an effective Hamiltonian operator which conveniently describes vibrational spectra of linear tetratomic molecules, including both stretching and bending modes. For a linear symmetrical four-atom molecule C2H2, the highly excited vibrational levels are obtained by applying the u(4) algebraic approach. We have found that the spectra are made up of a clustering structure. The number of levels in one cluster depends on the total quantum number of stretching and bending vibrations. In addition, some other properties, such as the level assignment and the labeling of calculated theoretical results, are also discussed
[en] A set of general expressions for photoionization cross sections of atoms or molecules embedded in a medium and a dielectric influence function are derived based on Maxwell's equations and the Beer-Lambert's law in this work. The applications are performed for the photoionization process of solid gold both in the Clausius-Mossotti (virtual cavity) model and the Glauber-Lewenstein (real cavity) model firstly. The results show that the present theoretical expressions of photoionization cross section can be used to describe the photoionization process of atoms in condensed matter properly.
[en] The quasi-classical trajectory (QCT) calculation are carried out for both exchange and abstraction processes of the reaction H + HS on a newly constructed high-quality lowest triplet state potential energy surface (3A″) of H2S. The integral cross section and the product polarization are investigated over the collision energy range of 0.1-2.0 eV for the reagent HS at the different vibrational and rotational states (v = 0 - 3, j = 0 - 3). The QCT-calculated integral cross sections are in good agreement with the previous QM results at the total angular momentum J = 0 as a function of collision energy for the H + HS (v = 0, j = 0) reaction. The detailed study of the dynamics properties for the title reaction is presented. (authors)
[en] The anharmonic force fields and spectroscopy constants for the ground electronic state of copper hydrosulfide (CuSH) have been investigated using various theoretical methods (MP2, B3LYP, B3P86, B3PW91) and basis sets (cc-pVDZ, cc-pVTZ). It turns out that the MP2/cc-pVTZ theoretical level is reasonable to study the molecular spectroscopic properties of CuSH. The calculated molecular structure, rotational constants, vibrational frequencies, centrifugal distortion constants, vibration–rotation interaction constants, force constants and Coriolis coupling constants of CuSH can be utilized to provide theoretical predictions of the spectroscopic properties and can be conducive to chemical applications such as the hydrodesulfurisation of fossil feed-stocks. Besides, the calculated force constants, evaluated in mass-weighted normal coordinates using a finite-difference approach, can be used to analyze the potential energy surface of CuSH. In addition, the anharmonic force fields of CuSD have been also investigated using the MP2 method. (paper)
[en] The time-dependent-wave-packet method has been applied to calculate the kinetic energy distribution of H+ ion resulting from the recollision between the electron and its parent ion H2+(X2Σg+) within subfemtosecond time scale. The recollision probabilities between the electron and H2+ as a function of time have also been obtained. Also, an accurate quantum dynamics method has been applied to describe the motion of both the electron and the nuclear wave packets with attosecond resolution. The calculated results are in good agreement with experimental ones
[en] The ionization spectrum of sulfur dioxide has been successfully studied by using the symmetry-adapted-cluster configuration-interaction (SAC-CI) general-R and SD-R methods and the basis set correlation-consistent polarized valence triple-zeta (cc-pVTZ). The SAC-CI general-R method reproduces the experimental spectrum well for both the main peaks and the satellite peaks of ionization spectrum of SO2. The sequence of ionic states corresponding to main peaks of SO2 has been re-determined according to the SAC-CI conclusions and it is reordered as X-bar 2A1, Ã2B2, B-bar 2A2, C-bar 2B1, D-bar 2A1, Ē2B2 and F-bar 2A1. Besides, the equilibrium structures and adiabatic ionization potentials (AIPs) of ionic states of main peaks of SO2 are calculated by using the SAC-CI SD-R method. (atomic and molecular physics)
[en] The influence of the local-field effect on the photoabsorption cross sections of the atoms which are embedded in the macroscopic medium has been studied by a set of alternative expressions in detail. Some notes on the validity of some different local-field models used to study the photoabsorption cross sections of atoms in condensed matter have been given for the first time. Our results indicate that the local fields can have substantial and different influence on the photoabsorption cross section of atoms in condensed matter for different models. Clausius-Mossotti model and Onsager model have proved to be more reasonable to describe the local field in gas, liquid, or even some simple solid, while Glauber-Lewenstein model probably is wrong in these conditions except for the ideal gas. A procedure which can avoid the errors introduced by Kramers-Kronig transformation has been implemented in this work. This procedure can guarantee that the theoretical studies on the local field effects will not be influenced by the integral instability of the Kramers-Kronig transformation
[en] Highlights: • The symmetry-broken effects induced by nuclear vibrations. • Electron momentum spectroscopy of core electrons. • A new methodology based on quantum mechanics considers nuclear vibrations. The vibronic coupling effect is usually studied by invoking the breakdown of Born-Oppenheimer approximation. The present study shows that the symmetry-broken effect induced by nuclei vibrations can also lead strong impact on the electronic states under the framework of Born-Oppenheimer approximation. This adiabatic-invoking vibrational effect on electron momentum spectroscopy of ethylene (C2H4), ethane (C2H6) and methanol (CH3OH) was studied with quantum mechanical method. The results show that electron momentum spectroscopy of localized electrons, especially core electrons in axial symmetric geometry molecules can be affected unusually and strongly by several asymmetric vibrational modes.