M. M. Fujimoto

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.

A dissociative electron attachment cross-section estimator

Dissociative electron attachment (DEA) is the major process where molecules are destroyed in low-energy plasmas. DEA cross sections are therefore important for a whole variety of applications but are both hard to measure or compute accurately. A method for estimating DEA cross sections based a simple resonance plus survival model is presented. Test results are presented for DEA of molecular oxygen and molecular chlorine, for which experimental measurements are available for comparison, and SiBr and SiBr2, for which no previous data is available. The estimator has been implemented as part of Quantemol-N expert system which uses the R-matrix method to predict resonance positions and widths.

The method of continued fractions for electron (positron)-atom scattering

The method of continued fractions (MCF) of Horacek and Sasakawa (1983-5) is adapted to study low-energy electron scattering by atomic and ionic helium in the static-exchange approximation as well as positron scattering by atomic hydrogen in two- and three-channel coupling levels. This is the first real application of MCF to electron-ion and multi-channel scattering problems. For all the applications studied herein, the convergence of the iterative procedure is rapid and, in most cases, monotonic. Our study reinforces the potential of this method as an efficient tool for studying electron-atom scattering. Possible applications of MCF to treat electron-molecule scattering are also suggested.

Elastic and absorption cross sections for electron-nitric oxide collisions

In this paper, we report a theoretical study on electron scattering by an open-shell molecule in the low and intermediate energy range. More specifically, calculated elastic differential, integral and momentum transfer cross sections as well as absorption (excitation + ionization) cross sections in the 5-500 eV range are reported for e--NO collisions. In our calculation, a complex optical potential consisting of static, exchange, correlation-polarization plus absorption contributions, derived from a fully molecular wavefunction, is used to describe the electron-molecule interaction. The Schwinger variational iterative method combined with the distorted-wave approximation is applied to calculate scattering amplitudes. Comparison between calculated results and existing experimental and theoretical data is encouraging.

Vibrational cross sections for positron scattering by nitrogen molecules

We present a systematic study of low-energy positron collision with nitrogen molecules. Vibrational elastic and excitation cross sections are calculated using the multichannel version of the continued fractions method in the close-coupling scheme for the positron incident energy up to 20 eV. The interaction potential is treated within the static-correlation-polarization approximation. The comparison of our calculated data with existing theoretical and experimental results is encouraging.

Study of inner-shell excitation processes from N(1s) orbitals in N2O molecules by electron impact

A combination of the iterative Schwinger variational method with the distorted-wave approximation is applied to study excitations of a core-level electron in a triatomic molecule by electron impact. More specifically, we report calculated differential and integral cross sections for the X1Σ+ → 1,3Π(2σ → 3π) and X1Σ+ → 1,3Π(3σ → 3π) transitions in N2O in the 415–900 eV incident energy range. The RI(1:3) ratios, obtained via dividing the distorted-wave integral cross sections for transitions leading to the singlet core-excited states by those leading to triplet states, are also reported. The generalized oscillator-strength profiles for the singlet transitions have also been calculated at the incident energy of 3400 eV. The comparison of these quantities with the available theoretical and experimental data reported in the literature is encouraging.

Averaged electron collision cross sections for thermal mixtures of alpha-alanine conformers in the gas phase

A theoretical study of elastic electron collisions with 9 conformers of the gas-phase amino acid

Spin-exchange effects in elastic electron scattering from linear triatomic radicals

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Comparative study of elastic electron collisions on the isoelectronic SiN{sub 2}, SiCO, and CSiO radicals

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Comparative study for elastic electron collisions on C{sub 2}N{sub 2} isomers

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