Lee Mu-Tao

Elastic electron scattering by water molecules

Elastic differential and momentum transfer cross sections are reported for electron scattering by H2O at impact energies ranging from 4 to 50 eV. The iterative Schwinger variational method in the fixed-nuclei, static-exchange approximation is used to calculate the low partial wave scattering amplitudes and the higher partial wave contributions are included via closure using the Born approximation for a point-dipole. Comparison of our calculated cross sections with recent experimental and other theoretical results is encouraging.

Elastic differential cross section measurements for electron scattering from Ar and O2 in the intermediate-energy range

The authors report experimental elastic differential, integral and momentum transfer cross sections for electrons scattered by Ar and O2 in the impact energy range 300-1000 eV and in the angular range 5-140 degrees . In their experiments, the intensities of the elastically scattered electrons were obtained in the crossed-electron-beam-molecular-beam geometry and the absolute values of the cross section were derived through the relative-flow technique using N2 as the secondary standard. For both gases, the cross sections are compared with the available experimental and theoretical results.

Elastic electron scattering at acetylene at low and intermediate energies

The authors report calculated differential and integral cross sections for e-C2H2 collisions in the 10-200 eV energy range. These cross sections were derived from fixed-nuclei scattering amplitudes in such a way that the low angular momentum components are obtained using the Schwinger iterative method and the large ones are treated by a Born closure. Using this combined theory, it can be shown that the elastic differential cross sections obtained at the static-exchange level are nearly exact, even at higher energies. The inclusion of a semi-empirical polarization potential is discussed as well.

Low energy elastic scattering of electrons by hydrogen sulphide molecules

Elastic differential, integral and momentum transfer cross-sections for electron-H2S collisions are reported at impact energies ranging from 2 to 50 eV. The Schwinger variational iterative method in a fixed-nuclei static-exchange approximation is used to calculate the low partial-wave scattering amplitudes. Higher partial-wave contributions were taken into account through the Born approximation with a point-dipole potential. Comparison of our calculated cross-sections with recent experimental and theoretical results is encouraging.

Cross sections for electron impact excitation of the low-lying electron states of CO2

Distorted-wave cross sections for the excitation of eight low-lying excited states (1,3 Sigma u+, 1,3 Pi g, 1,3 Pi u and 1,3 Delta u) of CO2 by electrons in the 25 to 60 eV energy range are presented. The authors report both differential and integral cross sections.

Validity of the distorted-wave approximation (DWA) for inelastic e--H2 scattering

The validity of the distorted-wave approximation for e--H2 scattering is tested through a comparative study with the two-channel Schwinger multichannel method. Calculated differential cross sections are reported for the excitations to b 3 Sigma u+, a 3 Sigma g+ and c 3 Pi u states in the energy range covering from near threshold up to 30 eV. General good agreement is observed between both theories for incident energies above 20 eV.

Application of a new variational functional for electron-molecule collisions: an extension of the Schwinger variational principle

Discusses a variational functional for scattering theory which has been recently proposed by Takatsuka and McKoy (1980). It is shown that this functional can provide results with a purely discrete set of functions which are approximately equivalent to those obtained by Lucchese et al. (1980) from the first iteration of the iterative Schwinger method. Applications to the scattering of electrons by systems including CO+ and LiH illustrate this relationship and other features of the method.

Total cross sections for electrons scattered from gases: 0.5-3.0 keV range on Ar

Absolute total cross sections for electron scattering on Ar have been measured over the energy range of 0.5-3.0 keV. The correction due to the small-angle scattering was carried out using the theoretical differential elastic and inelastic cross sections. The corrected total cross sections agree well with the earlier experimental and theoretical results. The comparison with the high-energy Born theory is discussed.

Studies of vibronic excitations of H2 by electron impact

The authors report rotationally unresolved vibro-electronic cross sections and branching ratios associated with the X 1 Sigma +g to d 3 Pi u electronic transition in H2, using the distorted-wave approximation within the adiabatic-nuclei framework. The present study shows that the Franck-Condon approximation (FCA) can provide reliable cross sections. The calculated branching ratios associated with the vibro-electronic transitions exhibit some oscillations at low energies; however, their magnitudes agree well with the FCA predictions.

Electronic correlation effects of the target in excitation cross sections by electron impact in H

The authors report differential cross sections for the X 1 Sigma +g to b 3 Sigma +u, a 3 Sigma +g and c 3 Pi u excitations of H2 by electron impact at 20 eV. They are particularly interested in studying correlation effects of the target on these cross sections. Comparisons are made with available theoretical and experimental results.