P H Norrington

RMATRX1: Belfast atomic R-matrix codes

Abstract RMATRX1 is a general program to calculate atomic continuum processes using the R -matrix method, including electronatom and electron-ion scattering, and radiative processes such as bound-bound transitions, photoionization and polarizabilities. Calculations can be either in LS -coupling, or in an intermediate-coupling scheme by including terms of the Breit-Pauli Hamiltonian. This version supersedes all previous versions, is well-optimised, and contains many new and improved features.

Low-energy electron scattering by Fe XXIII and Fe VII using the Dirac R-matrix method

Collision strengths for the low-energy scattering of electrons by Fe XXIII and Fe VII have been calculated using the Dirac R-matrix method. For Fe XXIII the results for the excitation from the ground state (1s22s2)1Se0 to the third level (1s22s2p) 3Po1 have been compared with earlier Breit-Pauli and non-relativistic calculations. The agreement is found to be good as expected since relativistic effects are important but not dominant. For Fe VII, excitations between the first nine levels have been considered and a comparison made with an earlier distorted-wave calculation. These are both extensive tests of the method and demonstrate that it can be used to produce reliable electron-ion collision data.

The K-shell ionisation of atoms by relativistic protons

The K-shell ionisation is investigated using an extension of the first-order time-dependent perturbation-theory treatment of Moller (1932) taking Dirac plane waves for the description of the incident and scattered protons and the Darwin approximation for the relativistic wavefunctions of the K-shell atomic electrons and the ejected electron. The differential cross sections delta 2 sigma / delta k delta q and d sigma /dk, where k is the wavenumber of the ejected electron and hq is the momentum change of the proton, are calculated. The double differential cross section for collisions in which a change of spin of the atomic electron occurs is less sharply peaked for small q, and has a broader overall distribution with respect to q, than the double differential cross section for collisions without spin change, although being much less in magnitude than the latter for small q. This leads to total K-shell ionisation cross sections sigma with significant contributions coming from collisions with spin change of the atomic electron for large atomic numbers at high energies of impact.

Magnetic dipole transitions in 4d{sup N} configurations of tungsten ions

Magnetic dipole transitions between the levels of ground

Relativistic allowed and forbidden transition probabilities for fluorine-like Fe XVIII

4{d}^{N}

Rate coefficients for electron impact excitation of helium-like ions within the Dirac R-matrix approach

configurations of tungsten ions were analyzed by employing a large basis of interacting configurations. Previously introduced configuration interaction strength between two configurations was used to determine the configurations with the largest contribution to wave functions of atomic states for the considered configurations. Collisional-radiative modeling was performed for the levels of the ground configuration coupled through electric dipole transitions with

Energy Levels and Transition Probabilities for Boron-Like Fe XXII

4{p}^{5}4{d}^{N+1}

Electron-impact excitation of Fe II. Collision strengths and effective collision strengths for low-lying fine-structure forbidden transitions.

and

Dirac-Fock energy levels and transition probabilities for oxygen-like Fe XIX

4{d}^{N\ensuremath{-}1}4f

Spontaneous transition rates for electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2) and magnetic quadrupole (M2) transitions for He-like calcium and sulfur ions

configurations. New identification of some lines observed in the electron-beam ion trap plasma was proposed based on calculations in which wavelength convergence was reached.