Xu Ke-Zun

Absolute total cross section measurement for electron scattering on in the energy range 600 - 4250 eV

Absolute total cross sections for electron scattering on nitrous oxide molecules have been measured between 600 and 4250 eV. It has been noticed that and carbon dioxide exhibit similarities in the energy dependence of their total cross sections. The results have been compared with available theoretical and experimental results. No previous data for impact energies above 500 eV have been found in the literature.

Experimental and theoretical investigations of absolute optical oscillator strengths for valence excitations of nitric oxide

The absolute optical oscillator strength density spectra of nitric oxide in the energy region of 5.0-22.0 eV have been measured by a high-resolution fast-electron energy loss spectrometer. With the calculated results obtained by the multiscattering self-consistent-field method and channel characteristics, the strongly overlapped spectra in the energy region of 7.5-9.3 eV have been analysed and the corresponding partially vibrationally resolved optical oscillator strengths have been estimated from the experimental spectra.

The non-destructive threshold of the graphite surface by STM in the ultra-fast pulse mode

In this paper single ultra-fast voltage pulses are introduced to the Pt/Ir tip of a scanning tunnelling microscope (STM), and the non-destructive threshold of the graphite surface is studied systematically in a wide range of pulse durations (from 104 to 8ns). Considering the waveform distortion of the pulses at the tunnelling region, this paper gives the corrected threshold curve of pulse amplitude depending on pulse duration. A new explanation of threshold power has been suggested and fits the experimental results well.

Exchange and final channel screening effects in (e, 2e) processes

The DS3C model has been improved by taking into account the final channel screening effects. The triple differential cross sections for electron impact ionization of helium at an incident energy of 40 eV are considered. The results of the present DS3C model are compared with the absolute measurements and those of other theoretical models. It has also been shown in which situation the exchange effects are crucial.

Experimental verification of the anomalous Čerenkov radiation

Abstract The character of the radiation caused by electrons moving through air, bromine vapor and sodium vapor was studied experimentally using a 90 Sr β-source. It was discovered that the angular distribution of the radiation has obvious anisotropy and that the radiation emitted has a line spectrum and is plane polarized. The existence of the anomalous Cerenkov radiation was thus experimentally verified.

Optically Forbidden Excitations of 2s Electron of Neon Studied by Fast Electron Impact

The electron energy loss spectrum in the energy region of 42-48.5 eV of neon is measured with an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of 2500 eV. Besides the dipole-allowed au-toionization transitions of 2s-1 np (n = 3,4) and 2p-2 3s3p, the dipole-forhidden ones of 2s-1 ns (n = 3 — 6) and 2s-1 3d are observed. The line profile parameters, i.e. Er, F and q for these transitions, are determined, and the momentum transfer dependence behaviour is discussed.

Electron Momentum Distributions of the Highest Occupied Molecular Orbital of CF3Br: Delocalization of Halogen Lone-Pair Orbitals

The highest occupied molecular orbital (HOMO) of trifluorobromomethane (CF3Br) is studied by binary (e,2e) electron momentum spectroscopy. The experimental momentum profile of the HOMO is compared with the Hartree–Fock (HF) and density functional theory (DFT-B3LYP) calculations. The calculated results largely depend on the size of basis sets rather than theoretical methods. Both the HF and DFT calculations using the 6-311++G** basis set give a good explanation to the experiment. Delocalization of halogen lone-pair orbitals in the series molecules CF3X (X= F, Cl, Br) has been investigated.

Optical Oscillator Strengths for 32S → 42P and 32S → 52P Excitations of Na

The electron-energy-loss-spectrum of sodium has been measured in discrete region at a 1.5 keV impact energy and a mean scattering angle of 0°. The relative optical oscillator strength density spectrum of the valence shell of sodium was established by using the dipole (e, e) method and then normalized to the theoretical optical oscillator strength of the 32S → 32P excitation. The optical oscillator strengths of the 32S → 42P and 32S → 52P excitations obtained in the present work are 0.014 ± 0.002 and 0.0026 ± 0.0004, respectively. Theoretical values of optical oscillator strengths for 32S → n2P (n = 3 - 5) excitations of sodium were obtained by using the relativistic configuration interaction method, which are 0.97, 0.012, and 0.0025, respectively.

Inner Shell Excitations of Lithium Studied by Fast Electron Impact

Electron energy loss spectra for the inner shell excitations of atomic lithium are measured at an incident electron energy of 2500eV and scattering angles of 0°, 2°, 4° and 6°. Two optically forbidden transitions of (ls2s2)2 S and (1s2s3S)3s2 S are observed. The generalized oscillator strength ratios for Is{2s2p3 P)2P0 to 1s(2s2p1P)2P0 were determined, and they are independent of the momentum transfer.

Generalized oscillator strengths for some higher valence-shell excitations of krypton atom

The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ← 4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.