[en] In this paper, Ab initio scattering calculations for low-energy electron collisions with BeCl₂ molecule have been carried out. The calculations were performed with R-matrix method in the static exchange (SE), static exchange plus polarization (SEP) and close coupling (CC) models for electron energies ranging from 0 to 10 eV. We found one shape resonance state with B_2u symmetry and the other one with B_3u symmetry in each electron scattering model. We discuss the changes of these resonance states with the polarization effect, and obtain the convergence cross section and resonance state results. The differential scattering cross section (DCS) and momentum transfer cross section (MTCS) of electrons collision with BeCl₂ molecule were first calculated by using the POLYDCS program. Current research results will provide important cross-sectional data for astrophysics and plasma physics. (authors)

[en] In this paper R - matrix method is used to study the elastic scattering cross section and the dynamic process of the low - energy electron scattering with the acetylene molecule. The static exchange model (SE) and the static exchange plus polarization model (SEP) were used. The results show that the elastic scattering cross section predicted by the current SEP model is in good agreement with the experimental and theoretical results. The SE model predicts a π - shaped resonant state at 4.75 eV with a width of 3.0 eV. The position of the resonant state decreases to 2.65 eV in the SEP model and 1.5 eV in width. The resonance is derived from the symmetry of B_2g and B_3g. The theoretical predicted resonant position agrees well with the experimental data. In addition, we get the differential scattering cross sections (DCSs) calculated by K - matrix element based on R - matrix. The results are in good agreement with the existing theoretical results. (authors)

[en] Ab initio scattering calculations for low-energy electron collisions with PH₂, PF₂, and PCl₂ are performed using the R-matrix method in this study. The elastic integral, differential, and momentum transfer cross sections and the excitation cross sections from the ground state to the five low-lying electron excited states are presented in the energy region of 0.01–15 eV. The target states are represented by including correlations via a configuration interaction technique. The resonant states are detected and identified. The sensitivity of the results to changes in the theoretical model is checked by comparing predictions from a variety of approximations including static exchange, one state close-coupling (CC), and many-state CC approximations. The similarities and differences among the resonances of these three radicals are discussed. (paper)

[en] We report on a computational investigation of electron scattering by ketene in the correlated and uncorrelated approximations using the R-matrix method for energies ranging from 0 to 10 eV. The target wave functions are based on different-size basis sets and are tested to obtain the reliable properties of electronic states for the ketene molecule. The calculated elastic integral cross sections present two low-lying π* shape resonances belonging to "2B_1 and "2B_2 symmetries. Two higher-lying resonances of "2B_1 symmetry, one core-excited shape resonance and one Feshbach resonance, are detected in the excitation cross sections. These resonances are in agreement with the available data in the literature. The Born correction is used to obtain converged cross sections for the L > 4 partial waves excluded from the R-matrix calculations. We compare the elastic cross sections with the available data for CO_2. The effective collision frequencies over a wide electron temperature range (100–30 000 K) are calculated using the data of the momentum-transfer cross section. (paper)

[en] Using scanning tunneling spectroscopy, we have studied the interface effect on quantum well states of Pb thin films grown on various metal-terminated (Pb, Ag, and Au) n-type Si(111) surfaces and on two different p-type Si(111) surfaces. The dispersion relation E(k) of the electrons of the Pb film and the phase shift at the substrate interface were determined by applying the quantization rule to the measured energy positions of the quantum well states. Characteristic features in the phase shift versus energy curves were identified and were correlated to the directional conduction band of the silicon substrate and to the Schottky barrier formed between the metal film and the semiconductor. A model involving the band structure of the substrate, the Schottky barrier, and the effective thickness of the interface was introduced to qualitatively but comprehensively explain all the observed features of the phase shift at the substrate interface. Our physical understanding of the phase shift is critically important for using interface modification to control the quantum well states. (paper)

[en] With high energy resolution scanning tunneling spectroscopy, we have studied the superconductivity of a set of individual Pb islands grown on a Si(111) surface. By systematically examining 8 and 9 ML thick Pb islands with a large range of lateral sizes, we have found that their superconducting transition temperatures follow the same trend of gradual suppression on decreasing the size of the island, despite having a different density of states (DOS) at the Fermi level. This behavior is completely different from the sudden drop of transition temperature observed in the ensemble Pb particles system. Our systematic analysis in treating the temperature-dependent pseudogap state for the Pb islands has revealed a critical region in superconductivity that originates from fluctuations and was predicted by theory. Our further analysis has indicated that when the size decreases, the DOS change at E_F due to the discretization of electronic levels wins over the phonon softening for Pb islands and results in a net decrease of the superconductivity temperature. (paper)

[en] This work adopts the density functional B3P86/cc-PVTZ method to optimize the ground state structure and the time dependent density functional theory TDDFT/cc-PVTZ to study the absorption spectra, excitation energies and oscillator strength of diazasilene molecule SiNN under different external electric fields. The results show that the absorption spectra, excitation energies and oscillator strengths of SiNN molecule are affected strongly by the external electric fields. The important results are that the SiNN molecule has a violet light absorption spectrum about 376∼401 nm region under a certain external electric fields. Also, the luminescence mechanism of visible light for SiNN molecule is investigated. It is fond that the calculated emission spectra located in visible light region are in good agreement with experimental data. (authors)

[en] We present elastic integral cross sections for electron collisions with ethylene oxide and thiirane. The calculations were performed with R-matrix method in the static-exchange and static exchange polarization approximations for electron energies ranging from 0.01 to 15 eV. We found two shape resonances in the ²B₁ and ²B₂ symmetry in each molecule. We also detected one shape resonance in the ²A₁ symmetry for thiirane. The positions of the resonances agree well with available results. We shed some light on the nature of the resonances of these two compounds together with molecular orbital calculations. The similarities and differences among the resonances are discussed. Graphical abstract: .

[en] The equilibrium geometries of the first three singlet excited states 1 ¹A'', 1 ¹A', 2 ¹A'' of methyl vinyl vinyl silicone molecule are calculated using the general-R method of symmetry adapted cluster-configuration interaction (SAC-CI) with 6-311 ++g^** basis set. The differences of structure parameters between the first three singlet excited states are compared. And then some property parameters of the first three singlet excited states 1 ¹A'', 1 ¹A', 2 ¹A'' of methyl vinyl silicone molecule, such as charge distribution, highest occupied molecular orbital, HOMO, lowest unoccupied molecular orbital, LU-MO, energy gaps etc. are investigated on the basis of having got stable structures of the three singlet excited states. The energy gap of 1 ¹A' state is found to be the smallest and the electrons of HOMO are more apt be excited. The corresponding vibration spectra of the three singlet states are calculated, and the vibration modes are obtained. In addition, the broken bonds mechanism of methyl vinyl silicone molecule on excited states is also analyzed, which are in better agreement with the experimental results. (authors)

[en] A high-sensitivity angle and energy dispersive multichannel electron momentum spectrometer with simultaneous detection in 2π angle range is presented. A newly designed double half wedge and strip anode position-sensitive detector is employed to collect the ionized and scattered electrons passing through a 90 deg. sector, 2π spherical electrostatic analyzer over azimuthal angle range of about 150 deg. for each. Experimental results on argon are presented to exhibit the performance of the spectrometer.