Studies of the photoionization cross sections of CH_4

We present cross sections and asymmetry parameters for photoionization of the 1t_2 orbital of CH_4 using static‐exchange continuum orbitals of CH^+_4 to represent the photoelectron wave function. The calculations are done in the fixed‐nuclei approximation at a single internuclear geometry. To approximate the near‐threshold behavior of these cross sections, we assumed that the photoelectron spectrum is a composite of three electronic bands associated with the Jahn–Teller components of the distorted ion. The resulting cross sections reproduce the sharp rise seen at threshold in the experimental data and are in good agreement with experiment at higher energy. The agreement between the calculated and measured photoelectron asymmetry parameters is, however, less satisfactory

Studies of electron-molecule collisions: Applications to e-H2O

We report elastic differential and momentum transfer cross sections for the elastic scattering of electrons by H2O for collision energies from 2 to 20 eV. These fixed-nuclei static-exchange cross sections were obtained using the Schwinger variational approach. In these studies the exchange potential is directly evaluated and not approximated by local models. The calculated differential cross sections, obtained with a basis set expansion of the scattering wave function, agree well with available experimental data at intermediate and larger angles. As used here, the results cannot adequately describe the divergent cross sections at small angles. An interesting feature of the calculated cross sections, particularly at 15 and 20 eV, is their significant backward peaking. This peaking occurs in the experimentally inaccessible region beyond a scattering angle of 120°. The implication of this feature for the determination of momentum transfer cross sections is described

Photoionization Cross Sections and Asymmetry Parameters for Ethylene

We present the results of applications of the iterative Schwinger variational method to obtain photoionization cross sections and phoelectron angular distributions for ionization out of the four outermost valence orbitals 1b_(3u), 1b_(3g), 3a_g and 1b_(2u) of ethylene for photon energies ranging from near threshold to 30 eV. The observed resonance-like maxima in the cross sections for ionization of the 1b_(3g) and 3a_g orbitals are reproduced in our calculations. The disagreement between our cross sections and the experimental data for the 1b_(3u) orbital below 17 e V is attributed to autoionization, which is not accounted for in our calculations

Elastic and rotational excitation cross sections for electron scattering by polyatomic molecules

In this work we present a theoretical study on electron scattering by both polar and nonpolar polyatomic molecules in the low-energy range. More specifically, we report calculated elastic and rotationally inelastic differential cross sections for electron scattering by CH4, H2O, and H2S in the (2.14-30)-eV range. Exact static-exchange plus model correlation-polarization potentials are used to represent the electron-molecule interaction. The Schwinger variational iterative method is used to solve the scattering equations. In addition, the adiabatic-nuclei-rotation approximation is applied to calculate rotational cross sections. The comparison of our calculated results with experimental and other theoretical data available in the literature is encouraging.80481

Elastic and rotational excitation cross-sections for electron-water collisions in the low- and intermediate-energy ranges

We present a theoretical study on electron-H2O collisions in the low- and intermediate-energy ranges. More specifically, we report calculated elastic differential, integral and momentum transfer cross-sections as well as rotational excitation cross-sections in the (2–500)-eV range. In our calculations, an optical potential is used to represent the electron-molecule interaction. The Schwinger variational method combined with the distorted-wave approximation is used to solve the scattering equations. The comparison of our calculated results with other theoretical and/or experimental data available in the literature is very encouraging

Elastic and total cross-sections for electron scattering by acetylene in the intermediate energy range

We present a joint theoretical-experimental study on electron scattering by C2H2 in the intermediate energy range. We report calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and absorption cross-sections at impact energies ranging from 10 to 500 eV. Also, experimental absolute elastic cross-sections are reported in the (50–500)-eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. The iterative Schwinger variational method, combined with the distorted-wave approximation, is used to solve the scattering equations. Experimentally, the angular distributions of the scattered electrons are converted to absolute cross-sections using the relative flow technique. The comparison of our calculated with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging