Low-energy electron collisions with water: elastic and rotationally inelastic scattering

Differential, integral and momentum transfer cross sections for the vibrationally elastic and rotationally inelastic scattering of electrons from water at low collision energies (E < 7 eV) are reported. The R-matrix method is used to compute the body-fixed T-matrices while the scattering calculations are performed within the fixed-nuclei approximation corrected with the standard Born-closure formula. Our calculations are compared with the very recent experimental results of Cho et al (2003 Radiat. Phys. Chem. 68 115). The differential and momentum transfer cross sections are in good agreement with the experimental results. The relative contribution of the rotationally inelastic processes is investigated in some detail. In particular, the importance of the pure elastic process at very low energy is emphasized

Electron impact dissociative excitation of water within the adiabatic nuclei approximation

The R-matrix method is used to calculate dissociative excitation cross sections for the four lowest-lying electronically excited states of H2O in the energy range 5-15 eV. For the first time calculations are performed taking into account the nuclear motion by means of an adaptation of the adiabatic nuclei approximation. Cross sections are compared with previous and new fixed-nuclei results and also experiments. Resonance positions and widths are calculated for different geometries of the water molecule

GTOBAS: fitting continuum functions with Gaussian-type orbitals

GTOBAS is a program for fitting Gaussian-type orbitals (GTOs) to Bessel and Coulomb functions over a finite range. The exponents of the GTOs are optimized using the method of Nestmann and Peyerimhoff [J. Phys. B 23 (1990) L773]. The appended module NUMCBAS provides the numerical Bessel and Coulomb functions required as input for the program. The use of GTO continuum basis sets is particularly important in electron–molecule scattering calculations when polyatomic targets are involved. Sample results for such calculations are also discussed

Photoionization of H₂ using the molecular R-matrix with time approach

We present results of the first calculations using the variational ab initio molecular R-matrix with time approach. We have calculated two and four-photon ionization cross sections for H2 and studied the effects of electron correlation and choice of the Gaussian atomic basis sets. Our results are compared with earlier calculations

Atomic and molecular suite of R-matrix codes for ultrafast dynamics in strong laser fields and electron/positron scattering

We describe and illustrate a number of recent developments of the atomic and molecular ab initio R-matrix suites for both time-dependent calculations of ultrafast laser-induced dynamics and time-independentcalculations of photoionization and electron scattering. © 2019 Published under licence by IOP Publishing Ltd

Atomic and molecular suite of R-matrix codes for ultrafast dynamics in strong laser fields and electron/positron scattering

Synopsis: We describe and illustrate a number of recent developments of the atomic and molecular ab initio R-matrix suites for both time-dependent calculations of ultrafast laser-induced dynamics and time-independent calculations of photoionization and electron scattering

Electron impact dissociative excitation of water within the adiabatic nuclei approximation

The R-matrix method is used to calculate dissociative excitation cross sections for the four lowest-lying electronically excited states of H2O in the energy range 5-15 eV. For the first time calculations are performed taking into account the nuclear motion by means of an adaptation of the adiabatic nuclei approximation. Cross sections are compared with previous and new fixed-nuclei results and also experiments. Resonance positions and widths are calculated for different geometries of the water molecule

Low-energy electron collisions with tetrahydrofuran

We have performed calculations for electron collisions with tetrahydrofuran (THF) using the UK molecular R-matrix codes. This is the largest molecule ever treated with the R-matrix method, and the only biologically relevant molecule of this size studied theoretically in the inelastic regime. We report ab initio integral cross section for incident energies up to 10 eV. No shape resonances have been found for this system, but a few core-excited resonances are present

Ab initio potential energy surfaces and nonadiabatic couplings involved in Be4++H2 electron rearrangement

10 pags., 12 figs., 2 tabs.We present the main characteristics of the energy and coupling surfaces for the BeH24+ quasimolecule, that are relevant to the dynamics of electron capture in Be4++H2 collisions in the 50 eV amu-1<E<1 keV amu-1 energy range. To construct the wave functions, we implemented a block-diagonalization method using the many electron description standard (MELD) program, which was recently modified to calculate nonadiabatic couplings. © 1997 American Institute of Physics.This work has been partially supported by the DGICYT Project No. PB93-0288-C02 and was performed in the frame of the agreement No. 8611/CF with the International Atomic Energy Agency. E.S.K. acknowledges Grant No. SAB 94- 0271 from the Ministerio de Educacion y Ciencia (Madrid)