I. Iga

A comparative experimental-theoretical study on elastic electron scattering by methane

Absolute differential cross sections for elastic electron scattering by methane have been measured at six incident electron energies between 5 and 100 eV and over scattering angles between 10° and 180°, using a crossed-beam electron spectrometer combined with a magnetic angle-changing device to extend the measurements to backward angles (125°–180°). Differential, integral and momentum-transfer cross sections are also calculated and reported for these energies. A complex optical potential was used to represent the electron–molecule interaction dynamics. The iterative Schwinger variational method combined with the distorted-wave approximation was used to solve the scattering equations. The comparison between our calculated and measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.

Elastic and total cross sections for electron-carbon dioxide collisions in the intermediate energy range

In this work, we report on a joint theoretical and experimental investigation on electron-CO2 collisions in the intermediate energy range. More specifically, the elastic differential, integral and momentum transfer cross sections as well as the grand total (elastic+inelastic) cross sections in the 30-500 eV energy range are calculated and reported. A complex optical potential consisting of static, exchange, correlation-polarization plus absorption contributions is used for the description of the electron-molecule interaction. The Schwinger variational iterative method combined with the distorted-wave approximation is applied to calculate the scattering amplitudes. In addition, experimental absolute elastic differential cross sections generated using the relative flow technique are reported in the 100-400 eV range. Comparison between the calculated results and present measured data and also existing experimental and theoretical results is encouraging.

A theoretical study on electron-methylidyne collisions in the low and intermediate energy range

In this work, we present a theoretical study on electron-methylidyne collisions in the low and intermediate energy range. More specifically, calculated elastic differential, integral and momentum transfer cross sections as well as grand total (elastic + inelastic) and absorption cross sections are reported in the 1-500 eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics in the present calculation while the Schwinger variational iterative method combined with the distorted-wave approximation is used to solve the scattering equations. Comparison between the present absorption cross sections with the existing experimental and theoretical data for electron-impact ionization processes is encouraging.

Elastic and total cross sections for electron-carbonyl sulfide collisions

In this paper, we report a joint theoretical-experimental study on electron-OCS collisions in the low- and intermediate-energy ranges. More specifically, elastic differential and integral cross sections, as well as grand total (elastic + inelastic) cross sections in the 0.4-600 eV energy range, are reported. A complex optical potential consisting of static, exchange, correlation-polarization plus absorption contributions, derived from a fully molecular wavefunction, is used for the electron-molecule interaction. The Schwinger variational iterative method, combined with the distorted-wave approximation, is applied to calculate the scattering amplitudes. Additionally, we also report measured elastic differential and integral cross sections in the 100-600 eV energy range determined using the relative-flow technique. Comparison between calculated results and present and existing experimental data, as well as with other theoretical results, is encouraging.

Electron scattering by methanol and ethanol: A joint theoretical-experimental investigation

We present a joint theoretical-experimental study on electron scattering by methanol (CH(3)OH) and ethanol (C(2)H(5)OH) in a wide energy range. Experimental differential, integral and momentum-transfer cross sections for elastic electron scattering by ethanol are reported in the 100-1000 eV energy range. The experimental angular distributions of the energy-selected electrons are measured and converted to absolute cross sections using the relative flow technique. Moreover, elastic, total, and total absorption cross sections for both alcohols are calculated in the 1-500 eV energy range. A complex optical potential is used to represent the dynamics of the electron-alcohol interaction, whereas the scattering equations are solved iteratively using the Padés approximant technique. Our calculated data agree well with those obtained using the Schwinger multichannel method at energies up to 20 eV. Discrepancies at high energies indicate the importance of absorption effects, included in our calculations. In general, the comparison between our theoretical and experimental results, as well as with other experimental data available in the literature, also show good agreement. Nevertheless, the discrepancy between the theoretical and experimental total cross sections at low incident energies suggests that the experimental cross sections measured using the transmission technique for polar targets should be reviewed.

Elastic and total cross sections for electron scattering by nitrogen molecule in the intermediate energy range

The Schwinger variational iterative method combined with the distorted-wave approximation is applied to the calculation of differential, integral and momentum transfer cross sections for elastic electron- scattering in the 20-800 eV energy range. In this study, a complex optical potential consisting of static, exchange, correlation-polarization plus absorption contributions, derived from a fully molecular wavefunction, is used for the electron-molecule interaction. It is shown that the introduction of absorption effects influences significantly the calculated differential cross sections in the intermediate and high incident energy range. Particularly, in the 50-300 eV range, the used model absorption potential has improved significantly the agreement between calculated results and the available experimental data.

Application of the method of continued fractions for electron scattering by linear molecules

The method of continued fractions (MCF) of Horacek and Sasakawa (1983) is adapted for the first time to study low-energy electron scattering by linear molecules. Particularly, we have calculated the reactance K-matrices for an electron scattered by hydrogen molecule and hydrogen molecular ion as well as by a polar LiH molecule in the static-exchange level. For all the applications studied herein, the calculated physical quantities converge rapidly, even for a strongly polar molecule such as LiH, to the correct values and in most cases the convergence is monotonic. Our study suggests that the MCF could be an efficient method for studying electron-molecule scattering and also photoionization of molecules.

Electronic excitation of the a3 ∑g+ and c3Πu states of H2 by electron impact using the method of continued fractions

Abstract In the present work we use a multichannel extension of the method of continued fractions (MCF) to study the low-energy electron-impact excitation in linear molecules at the two-state close-coupling level. In particular we have calculated the excitation cross sections for the X 1 ∑ g + → a 3 ∑ g + and X 1 ∑ g + → c 3 Π u transitions in H 2 for incident energies from near threshold to 30 eV. In our work, in contrast with the early two-state studies of Chung and Lin, no orthogonality constraint between the bound and continuum orbitals is imposed and the one-electron exchange terms are explicitly considered. In general our calculated cross sections are in good agreement with the results of the two-state Schwinger multichannel method. Our results for the a 3 ∑ g + are also in quite good agreement with the available experimental data. However, the cross sections for excitation of the c 3 Π u state differ significantly from the measured values at 20 and 30 eV, where they are available. The disagreement is attributed to the multichannel effects, not accounted for in this study.

Application of the method of continued fractions to low-energy electron scattering by the hydrogen molecule

Abstract The method of continued fractions (MCF) is applied to a systematic study of low-energy electron scattering by the hydrogen molecule. More specifically, we report differential, integral and momentum-transfer cross-sections for elastic e -H 2 collision in the 1.5–30 eV energy range. Our calculation is carried out using a static-exchange-polarization potential where the non-penetrating dipole-potential approximation is used to describe polarization effects. Calculated cross-sections are compared with the available experimental and theoretical data and show very good agreement at incident energies below the excitation threshold.

Elastic and absorption cross sections for electron scattering by ethylene in the intermediate energy range

In this work, we present a joint theoretical and experimental study on electron scattering by C2H4 in the intermediate energy range. Calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and absorption cross sections are reported at impact energies ranging from 10 to 500 eV. Also, experimental absolute elastic cross sections are reported in the 100–500 eV range. The measurements were performed using a crossed electron beam–molecular beam geometry. The angular distributions of the scattered electrons were converted to absolute cross sections using the relative flow technique. Theoretically, a complex optical potential was used to represent the electron–molecule interaction dynamics. The Schwinger variational iterative method combined with the distorted-wave approximation was used to solve the scattering equations. The comparison between our calculated and measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.