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

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

Diffusion on a face-centred cubic (111) surface in the presence of two non-equivalent adsorption sites

The interrelation between the surface symmetry and diffusion of adsorbed atoms is studied theoretically on a model face-centred cubic (fcc) (111) surface within the lattice-gas approximation. Diffusion proceeds through two non-equivalent sites on the fcc(111) surface. Short-range repulsive interaction between particles in the nearestneighbour non-equivalent sites is considered. This repulsion leads to a modification of the occupation numbers of both kinds of site and to changes in the energy barrier height for diffusion. The chemical surface diffusion coefficient, D, has been found to be strongly dependent on coverage, θ, the interaction strength between adatoms, and the difference between the activation energies, ∆E. In the case of a small ∆E value, the diffusion coefficient D increases with θ, as was expected for repulsive interaction. In our model the increase of D at θ=0.5 is reduced for higher values of ∆E and a local maximum of D(θ) is observed

Cross-section calculations for positron scattering from pyrimidine over an energy range from 0.1 to 10000 eV

We report a computational investigation of positron scattering by pyrimidine (C4H4N2) in the gas phase. Integral and differential cross sections have been calculated over a broad energy range by employing two distinct ab initio quantum scattering methods: the R-matrix method and a corrected form of the independent-atom representation, at low and high energies, respectively. Since pyrimidine is a strong polar molecule further dipole-induced excitations have been calculated in the framework of the first Born approximation. Good agreement is found between the different computational models and fair agreement is found with prior experimental results