M. Le Dourneuf

Atomic data from the IRON Project LI. Electron impact excitation of Fe IX

We calculate collision strengths and thermally averaged collision strengths for electron excitation between the one hundred and forty energetically lowest levels of Fe 8+ . The scattering target is more elaborate than in any earlier work and large increases are found in the excitation rates among the levels of the 3s 2 3p 5 3d electron configuration due to resonance series that have not been considered previously. The implications for solar and stellar spectroscopy have been discussed elsewhere (Storey & Zeippen 2001). We correct some errors that were made in generating the figures given in that paper and present corrected versions.

Low-energy behaviour of e?O scattering calculations

We report on calculations of low-energy e–O scattering using the R-matrix method. We compare cross sections for elastic scattering and excitation with experiment and recent theoretical values. We calculate elastic cross sections for the 3Pe ground state and cross sections for excitation to and between the 1De and 1Se states. We present detailed comparisons of elastic differential cross sections with experiment. We compare our approach using orthogonal orbitals with an approach using non-orthogonal orbitals. We investigate noticeable differences in results from different calculations towards the low-energy limit. We discuss the use of long-range polarization pseudostates and issues of convergence of results for an open-shell neutral atom for which exact target states are not available.

Electron impact excitation of Ni XIX using theR-matrix method

Collision strengths for all the transitions between the 15 lowest states of neon-like Ni XIX have been calculated for electron impact in the 80–140 Ry energy range. Configuration-interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the lower scattering partial waves (L≤9), while a no-exchange version of the same code has been used to compute efficiently the higher partial waves (L≥10). Effective collision strengths for 105 excitation transitions between the ground state 2s22p61Se and the 142s22p53l Rydberg states are tabulated for electron temperatures in the range logT=5.40 to logT=7.00, withT expressed in °K.

Theoretical study of electron-impact excitation of H(1s) into the states using a two-dimensional R-matrix propagator

Electron-impact excitation of the ground state of hydrogen into the states is studied by propagating the R-matrix in the two radial dimensions. Integral cross sections and resonance parameters are presented for collision energies from 0.75 Ryd (the n = 2 threshold) up to 0.96 Ryd (the n = 5 threshold). Below the n = 3 threshold, there is very good agreement with results from other methods and with experimental data. Between the n = 3 and n = 4 thresholds, integral cross sections are in better agreement with those of a coupled pseudostate method than with those of the J-matrix method, while resonance parameters are in good agreement with those of a 15-state R-matrix calculation.

Photoionization of ground and excited states of neon like K X

The close-coupling R-matrix method is used to calculate cross-sections for photoionization of K X from its ground and first three excited states. Configuration interaction wave-functions are used to represent two target states of K X I retained in the R-matrix expansion. The positions and effective quantum numbers for the Rydberg series converging to the excited state 2s2p6 2Se of the residual ion, are predicted.

Photoionization of ground and excited states of neon type Ti XIII

The R-matrix method is used to calculate the photoionization cross-section of Ti XIII from its ground and first three excited states. The results are obtained for photon energies ranging from the first ionization threshold to just above the second ionization threshold of the residual ion Ti XIV. Configuration interaction wavefunctions are used to describe the initial Ti XII and final Ti XIV states. The positions and effective quantum numbers for the Rydberg series converging to the excited state 2s2p6 2Se of the residual ion, are predicted.