We present an application of pseudopotentials to ab initio calculations elastic and electronically inelastic electron-molecule-collison cross sections. use the Schwinger multichannel method (SMC) implemented with local-density norm-conserving Bachelet, Hammann, Schl\"uter [Phys. Rev. B 26, 4199 (1982)]. In our procedure, core electrons protons are replaced by nonlocal but single-particle pseudopotential valence treated in a many-body framework, as SMC method. Our calculated integral...

The Schwinger multichannel method [K. Takatsuka and V. McKoy, Phys. Rev. A 30, 1734 (1984)], which is based on the variational principle for scattering amplitude [J. Schwinger, 72, 742 (1947)], was designed to account exchange, polarization electronically coupling effects in low-energy region of electron from molecules with arbitrary geometry. applications became more ambitious availability computer power combined parallel processing, use norm-conserving pseudopotentials improvement...

We discuss some recent developments in the implementation of Schwinger multichannel method for electron-molecule collision calculations. The evaluation matrix elements involving operator ${\mathrm{VG}}_{P}^{(+)}$V, previously accomplished by insertion a Gaussian basis on either side ${G}_{P}^{(+)}$, is now done direct numerical quadrature. This approach avoids necessity very large sets, allowing size to reflect only dynamical requirements scattering wave function. find that reduction...

We present a technique to generate Cartesian Gaussian bases for electronic configuration and cross-section calculations on molecules. The is specially useful pseudopotential work, when the cannot be tabulated because they depend specific choice of pseudopotential. © 1996 John Wiley & Sons, Inc.

We present a formulation for low-energy positron-molecule collisions based on the Schwinger multichannel method (SMC) which was previously adapted electron-molecule scattering. have preserved very important features of SMC such as its ability to deal with electronically inelastic scattering and applicability molecular targets arbitrary geometry. Our implementation also allows inclusion substantial number closed electronic channels represent polarization effects, are at low impact energies....

We report the results of a study on electron-target correlations in $^{2}\mathrm{\ensuremath{\Pi}}_{\mathrm{g}}$ shape resonance elastic e-${\mathrm{N}}_{2}$ scattering, using Schwinger multichannel formulation. The effects basis set, orbital representation, and closed-channel configurations are delineated. different roles radial angular compared. Our good agreement with recent calculation by Schneider Collins [Phys. Rev. A 30, 95 (1984)] linear algebraic-optical potential method whereas...

In this and two accompanying letters, the results of calculations cross sections for electron impact excitation b 3 Sigma u+ state H2, collision energies from near threshold to 30 eV, are presented. The obtained using a multichannel extension Schwinger variational principle at two-state level. quantitative agreement between integral these three studies is very good. Inclusion correlation terms in scattering wavefunctions, which relax orthogonality bound continuum orbitals seen affect...

Measured and calculated differential cross sections for elastic (rotationally unresolved) electron scattering from two primary alcohols, methanol $(\mathrm{C}{\mathrm{H}}_{3}\mathrm{O}\mathrm{H})$ ethanol $({\mathrm{C}}_{2}{\mathrm{H}}_{5}\mathrm{O}\mathrm{H})$, are reported. The measurements obtained using the relative flow method with helium as standard gas a thin aperture collimating target source. is applied without restriction imposed by pressure conditions on unknown gas. experimental...

We report elastic integral, differential and momentum transfer cross sections for low-energy electron scattering by the cellulose components β-D-glucose cellobiose (β(1 → 4) linked glucose dimer), hemicellulose component β-D-xylose. For comparison with β forms, we also obtain results amylose subunits α-D-glucose maltose (α(1 dimer). The integral show double peaked broad structures between 8 eV 20 similar to previously reported tetrahydrofuran 2-deoxyribose, suggesting a general feature of...

We report theoretical and experimental total cross sections for electron scattering by phenol (C6H5OH). The data were obtained with an apparatus based in Madrid the calculated two different methodologies, independent atom method screening corrected additivity rule (IAM-SCAR), Schwinger multichannel pseudopotentials (SMCPP). SMCPP Nopen-channel coupling scheme, at static-exchange-plus-polarization approximation, is employed to calculate amplitudes impact energies ranging from 5.0 eV 50 eV....

Elastic electron scattering cross sections from 5–30 eV are reported for the molecules C2H4, C2H6, C3H8, Si2H6, and GeH4, obtained using an implementation of Schwinger multichannel method distributed-memory parallel computer architectures. These results, within static-exchange approximation, in generally good agreement with available experimental data. calculations demonstrate potential highly computation study collisions between low-energy electrons polyatomic gases. The computational...

In this paper, we report integral and differential cross sections for the electronic excitation of H2 molecules by electron-impact. Our scattering amplitudes were calculated using Schwinger multichannel method within minimal orbital basis single configuration interactions (MOB-SCI) level approximation. Through use present strategy have investigated coupling effects among ground state first singlet triplet states same spatial symmetry. The five-state (nine degenerated states) close-coupling...

We used a multichannel extension of the Schwinger variational principle [K. Takatsuka and V. McKoy, Phys. Rev. A 24, 2473 (1981)] to study cross sections for excitation X $^{1}$ ${\mathrm{\ensuremath{\Sigma}}}_{\mathrm{g}}^{+}$\ensuremath{\rightarrow}b $^{3}\mathrm{\ensuremath{\Sigma}}_{\mathrm{u}}^{+}$, $^{3}\ensuremath{\Sigma}_{g}^{+}$, ${c}^{3}$${\ensuremath{\Pi}}_{u}$ transitions in ${\mathrm{H}}_{2}$ by low-energy electrons. These were obtained with two open channels each transition...

We report the first application of Schwinger multichannel formulation to low-energy electron collisions with a nonlinear polyatomic target. Integral and differential cross sections are obtained for e-${\mathrm{CH}}_{4}$ from 3 20 eV at static-plus-exchange interaction level. In these studies exchange potential is directly evaluated not approximated by local models. An interesting feature small-angle section ascribed polarization effects reproduced Our found be in reasonable agreement...

The Schwinger multichannel formulation has been applied to study the role of electron correlation in low-energy e-${\mathrm{N}}_{2}$ scattering. For five nonresonant partial-wave channels studied here, $^{2}\mathrm{\ensuremath{\Sigma}}_{\mathrm{g}}^{+}$, $^{2}\mathrm{\ensuremath{\Sigma}}_{\mathrm{u}}^{+}$, $^{2}\mathrm{\ensuremath{\Pi}}_{\mathrm{u}}$, $^{2}\mathrm{\ensuremath{\Delta}}_{\mathrm{g}}$, and $^{2}\mathrm{\ensuremath{\Delta}}_{\mathrm{u}}$, we find angular be much more important...

We report elastic differential and momentum transfer cross sections for the scattering of electrons by H2O collision energies from 2 to 20 eV. These fixed-nuclei static-exchange were obtained using Schwinger variational approach. In these studies exchange potential is directly evaluated not approximated local models. The calculated sections, with a basis set expansion wave function, agree well available experimental data at intermediate larger angles. As used here, results cannot adequately...

As a first application of the Schwinger multichannel theory, we have calculated integral and differential cross sections for electron-impact excitation transition $X ^{1}\ensuremath{\Sigma}_{g}^{+}\ensuremath{\rightarrow}b ^{3}\ensuremath{\Sigma}_{u}^{+}$ in ${\mathrm{H}}_{2}$ scattering energies from 13 to 30 eV at two-state level. We find good agreement between our results obtained previously close-coupling study. Our method does not rely on single-center expansions calculate body-frame...

We report on measurements of total cross sections for positron scattering from the fundamental organic molecule methane (CH${}_{4}$). The energy range these was 0.1--50 eV, whereas resolution $\ensuremath{\sim}$100 meV when our Ni moderator used and $\ensuremath{\sim}$260 W employed. To assist us in interpreting data, Schwinger multichannel calculations were performed at both static plus polarization levels approximation elastic 0.001 to 10 eV. These are found be quite good qualitative...

We present experimental electron-energy loss spectra (EELS) that were measured at impact energies of 20 and 30 eV angles 90° 10°, respectively, with energy resolution ∼70 meV. EELS for 250 incident electron over a range between 3° 50° have also been moderate (∼0.9 eV). The latter used to derive differential cross sections generalised oscillator strengths (GOS) the dipole-allowed electronic transitions, through normalization data elastic scattering from benzene. Theoretical calculations...

We report elastic differential, integral, and momentum transfer cross-sections for H2X molecules (X: O, S, Se, Te) obtained at the static exchange level of approximation. The energy range considered was from 2 up to 30 eV H2O 5 other molecules. Our calculations were performed with Schwinger multichannel method pseudopotentials [M. H. F. Bettega, L. G. Ferreira, M. A. P. Lima, Phys. Rev. A 47, 1111 (1993)], combined a Born closure procedure in order account long-range potential due permanent...

We use the wave function from Schwinger multichannel method to calculate ${\mathit{Z}}_{\mathrm{eff}}$---an annihilation parameter of positron-atom (or molecule) scattering. These ${\mathit{Z}}_{\mathrm{eff}}$ are evaluated (N+1)-particle and calculated in a fully ab initio way (in quantum chemistry sense). Our first applications for positron scattering against He atoms ${\mathrm{H}}_{2}$ molecules. results both systems excellent agreement with experimental data at thermal energies.

To assess the accuracy with which polarization is represented in Schwinger multichannel formulation, we have calculated elastic integral and differential scattering cross sections for $e$-${\mathrm{H}}_{2}$ collisions from 1 to 10 eV. Our ab initio results are found be good agreement other recent theoretical studies a variety of experimental data including measured sections. method designed applicable electronically inelastic closedshell targent molecules arbitrary geometry.