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 report on the shape resonance spectra of uracil, 5-fluorouracil, and 5-chlorouracil, as obtained from fixed-nuclei elastic scattering calculations performed with Schwinger multichannel method pseudopotentials. Our results are in good agreement available electron transmission spectroscopy data, support existence three π* resonances uracil 5-fluorouracil. As expected, anion states more stable substituted molecules than uracil. Since stabilization is stronger lowest this system becomes a...

We report cross sections for elastic electron scattering by gas phase glycine (neutral form), obtained with the Schwinger multichannel method. The present results are first a new implementation that combines parallelization OpenMP directives and pseudopotentials. position of well known π* shape resonance ranged from 2.3 eV to 2.8 depending on polarization model conformer. For most stable isomer, result (2.4 eV) is in fair agreement transmission spectroscopy assignments (1.93 ± 0.05 available...

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....

We recently extended the electron propagator theory to any type of quantum species based in framework Any-Particle Molecular Orbital (APMO) approach [J. Romero, E. Posada, R. Flores-Moreno, and A. Reyes, J. Chem. Phys. 137, 074105 (2012)]. The generalized particle molecular orbital (APMO/PT) was implemented its quasiparticle second order version LOWDIN code applied calculate nuclear effects binding energies proton systems [M. Díaz-Tinoco, V. Ortiz, 138, 194108 (2013)]. In this work, we...

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 positron binding energies (PBEs) for the 20 standard amino acids in global minimum, hydrogen-bonded, and zwitterionic forms. The calculations are performed at any-particle molecular-orbital (APMO) Hartree-Fock (HF), Koopmans' theorem (KT), second-order M\"oller-Plesset (MP2), propagator (P2) levels of theory. Our study reveals that APMO KT P2 methods generally provide higher PBEs than HF MP2 methods, respectively, with only a fraction computational costs latter. also discuss impact...

The valence anion states of the potential radiosensitisers 5-bromouracil and 5-iodouracil were investigated through elastic scattering 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...

Total electron scattering cross sections, from para-benzoquinone, for impact energies ranging between 1 to 200 eV, have been obtained by measuring the attenuation of a linear beam under magnetic confinement conditions. Random uncertainty limits on these values found be within 5%. Systematic errors, due axial conditions in combination with acceptance angle detector, evaluated integrating our calculated independent atom model screening corrected additivity rule and interference term elastic...

We report on integral-, momentum transfer- and differential cross sections for elastic electronically inelastic electron collisions with furfural (C5H4O2). The calculations were performed two different theoretical methodologies, the Schwinger multichannel method pseudopotentials (SMCPP) independent atom screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. SMCPP N energetically open electronic states (Nopen) at either static-exchange (Nopen...

We report integral cross sections for elastic electron scattering by the lignin subunits phenol, guaiacol, and $p$-coumaryl alcohol. Our calculations employed Schwinger multichannel method with pseudopotentials indicate three to four ${\ensuremath{\pi}}^{*}$ shape resonances each of these systems, suggesting that low-energy electrons could efficiently transfer energy into matrix. also discuss dissociation mechanisms based on calculated sections, available experimental data, virtual orbital...

Electron induced fragmentation of 2-thiouracil.

We report sufficient theoretical evidence of the energy stability e+ ⋅H22- molecule, formed by two H- anions and one positron. Analysis electronic positronic densities latter compound undoubtedly points out formation a covalent bond between otherwise repelling hydride anions. The lower limit for bonding molecule is 74 kJ mol-1 (0.77 eV), accounting zero-point vibrational correction. non fundamentally distinct from positron attachment to stable molecules, as process characterized affinity,...

We report results from a joint theoretical and experimental investigation into electron scattering the important organic species phenol (C6H5OH). Specifically, differential cross sections (DCSs) have been measured calculated for electron-impact excitation of electronic states C6H5OH. The measurements were carried out at energies in range 15-40 eV, scattered-electron angles between 10° 90°. energy resolution those experiments was typically ∼80 meV. Corresponding Schwinger multichannel method...

The efficient decomposition of nitroimidazoles (NIs) by low energy electrons is believed to underlie their radiosensitizing properties. Recent dissociative electron attachment (DEA) measurements showed that methylation at the N1 site unexpectedly suppresses electron-induced reactions in 4(5)-NI. We report theoretical results provide a clear interpretation astounding finding. Around 1.5 eV, DEA into several fragments are initiated π* resonance, not considered previous studies. autoionization...

We report measured and calculated cross sections for elastic scattering of low-energy electrons by the alcohols $n$-propanol $n$-butanol in gas phase. The measurements were carried out using relative-flow method with an aperture source rather than a conventional tube or capillary-array source, eliminating need to know molecular diameters. calculations employed two different implementations Schwinger multichannel variational included polarization effects. differential are dominated strong...

We report cross sections for low-energy elastic electron scattering by pyrrole, obtained with the Schwinger multichannel method implemented pseudopotentials. Our calculations indicate π∗ shape resonances in B1 and A2 symmetries, two σ∗ A1 symmetry (the system belongs to C2v point group). The present assignments of are very close those previously reported isoelectronic furan molecule, agreement transmission spectra. lowest-lying anion is localized on N–H bond provides a dissociation...

We report momentum transfer cross sections for elastic collisions of low-energy electrons with the HCOOH···(H2O)n complexes, n = 1, 2, in liquid phase. The scattering were computed using Schwinger multichannel method pseudopotentials static-exchange and plus polarization approximations, energies ranging from 0.5 eV to 6 eV. considered ten different structures HCOOH···H2O six HCOOH···(H2O)2 which generated classical Monte Carlo simulations formic acid aqueous solution at normal conditions...

We report on measurements of total cross sections (TCSs) for positron scattering from the fundamental organic molecule formaldehyde (CH2O). The energy range these was 0.26–50.3 eV, whereas resolution ~260 meV. To assist us in interpreting data, Schwinger multichannel level calculations elastic CH2O were also undertaken (0.5–50 eV). These calculations, incorporating an accurate model target polarization, are found to be good qualitative agreement with our measured data. In addition, order...

We report on a joint theoretical and experimental investigation into the electron-induced fragmentation of 2-chloroadenine, for electrons up to 12 eV. Our results suggest that 2-chloroadenine can be considered as potential radiosensitiser.