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[en] The positron–electron annihilation gamma-ray spectra of methanol have been studied in the present work. The contributions of the bound electrons to the Doppler-shift of gamma-ray spectra have been analysed as well. These bound electrons are divided into three groups: core, inner valence and outer valence rather than the conventional two groups: core and valence in the positron annihilation process in the present work. The results obtained show a dominance of the inner valence electrons of methanol rather than the electrons occupied in the highest occupied molecular orbital (HOMO) in the positron–electron annihilation process. These inner valence electrons occupied in 3a′ and 4a′ orbitals consist of over 80% outermost atomic 2s electrons in oxygen and carbon atoms. That the positron prefers to annihilate with these outermost s electrons in atoms is suggested.
[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] 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.
[en] Based on the reduced parameter, the equations for equilibrium vapor pressure and density of hydrogen isotopes have been derived, which can be used below the critical point of D2. It is shown that the calculating results of the saturated vapor density with the corresponding state method is more accurate than that with the dew point method, and that Benedict-Webb-Robin equation is more reasonable than the ideal gas equation for calculating the filling pressure
[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 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] A common equation of state has been proposed to describe the P-V-T properties of isotope gases via analyzing molecular dynamic simulation formula and intermolecular potential energy function for isotope gases. Furthermore, the authors have realized this idea in isotope gas H2, D2 and T2. The Benedict-Webb-Rubin equation has been chosen as the common equation and its eight parameters fitted from 135 experimental data of gas H2. The calculated results of the new common equation are also in good agreement with the experimental data of gas H2 and D2, and the molecular dynamics simulation results of gas T2
[en] We develop the semi-closed orbit theory from two degrees of freedom to three non-separable degrees of freedom and put forward a new model potential for the Li Rydberg atom, which reduces the study of the system to an effective one-particle problem. Using this model potential and the closed orbit theory for three degrees of freedom, we calculate the recurrence spectra of Li Rydberg atom in perpendicular electric and magnetic fields. The closed orbits in the corresponding classical system have also been obtained. The Fourier transformed spectra of Li atom have allowed direct comparison between the resonance peaks and the scaled action values of closed orbits, whereas the nonhydrogenic resonance can be explained in terms of the new orbits created by the core scattering. Our result is in good agreement with the quantum spectra, which suggests that our calculation is correct.
[en] Because of the fundamental nature of condensed rare gases, their potentials and equations of state have been studied extensively in recent years. In the present work, based on ab initio calculations on many-body interactions, the MSV III potential proposed by Parson et al. for argon system has been modified, and the molecular dynamics method is employed to calculate the Hugoniot curve for liquid argon system. Comparisons are performed between theoretical Hugoniot curve and the experimental measurements. This demonstrates that the coincidence degree between the theoretical and the experimental results are significantly improved