Electron impact excitation of Ar XVII

Energies for the lowest 49 levels among the 1s(2) and 1snl (n = 2-5) configurations of Ar XVII have been calculated using the GRASP code of Dyall et al. (1989, Comput. Phys. Comm., 55, 424). Additionally, radiative rates, oscillator strengths, and line strengths are calculated for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Furthermore, collision strengths have also been calculated for all the 1176 transitions among the above 49 levels using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2005, Comput. Phys. Commun., in preparation), over a wide energy range up to 580 Ryd. Resonances have been resolved in the threshold region, and effective collision strengths have been obtained over a wide temperature range up to log T-e = 7.2 K. Comparisons are made with the limited results available in the literature, and the accuracy of the data is assessed. Our energy levels are estimated to be accurate to better than 0.1%, whereas results for other parameters are probably accurate to better than 20%.

Electron impact excitation of O VI

Energy levels and radiative rates for transitions among the lowest 24 fine-structure levels belonging to the ls(2) nl (n <5) configurations of Li-like O VI have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have been computed over a wide energy range below 63 Ry, using the Dirac Atomic R- matrix Code. Resonances have been resolved in a fine energy mesh in order to calculate the effective collision strengths. Results for radiative rates, collision strengths, and effective collision strengths are presented for all transitions. Comparisons with other available results are made, and the accuracy of the present data is assessed. Energy levels are expected to be accurate to within 1%, while other parameters are probably accurate to better than 20%.

Electron impact excitation of C IV

Energy levels and radiative rates for transitions among the lowest 24 fine-structure levels belonging to the ls(2) nl (n <5) configurations of Li-like C IV have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have been computed over a wide energy range below 28 Ry, using the Dirac Atomic R- matrix Code. Resonances have been resolved in a fine energy mesh in order to calculate the effective collision strengths. Results for radiative rates, collision strengths, and effective collision strengths are presented for all transitions. Comparisons with other available results are made, and the accuracy of the present data is assessed. Energy levels are expected to be accurate to within 1%, while other parameters are probably accurate to better than 20%.

Electron impact excitation of Fe XIII

Energy levels and radiative rates for transitions among the lowest 97 fine-structure levels belonging to the (1s(2) 2s(2) 2p(6)) 3 s(2) 3p(2), 3s3p(3), 3s(2) 3p3d, 3p(4), 3s3p(2) 3d and 3s(2) 3d(2) configurations of Fe XIII have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have been computed using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2004). Radiative rates and oscillator strengths are tabulated for all allowed transitions among the 97 fine-structure levels, while collision strengths are reported for some transitions at a few energies above thresholds. Comparisons are made with the available results, and the accuracy of the data is assessed.

Electron impact excitation of Mo XXXIV

Energy levels and radiative rates for transitions among the lowest 60 fine-structure levels belonging to the (1s(2)) 2s(2)2p(5), 2s2p(6), and 2s(2)2p(4)3l configurations of F-like Mo XXXIV have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have also been computed over a wide energy range below 3200 Ry. using the Dirac Atomic R-matrix Code. Resonances have been resolved in a fine energy mesh in order to calculate the effective collision strengths. Results for radiative rates, collision strengths, and excitation rates are presented for transitions from the lowest three levels to higher lying states. Comparisons with other available results are made, and the accuracy of the present data is assessed. Energy levels are expected to be accurate to within 1%, while other parameters are probably accurate to better than 20%.

Excitation rates for transitions in Ca XV

Collision strengths for transitions among the energetically lowest 46 fine-structure levels belonging to the (1s(2)) 2s(2)2p(2), 2s2p(3), 2p(4), and 2s(2)2p3l configurations of Ca XV are computed, over a wide electron energy range below 300 Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2003). Resonances in the threshold region have been resolved in a fine energy mesh, and excitation rates are determined over a wide electron temperature range below 10(7) K. The results are compared with those available in the literature, and the accuracy of the data is assessed.

Electron impact excitation of carbon-like calcium

Collision strengths for transitions among the energetically lowest 46 fine-structure levels belonging to the (1s(2)) 2s(2)2p(2), 2s2p(3). 2p(4), 2s(2)2p3s, 2s(2)2p3p and 2s(2)2p3d configurations of Ca XV are computed. over an electron energy range of 50 less than or equal to E less than or equal to 300 Ryd. using the recent Dirac Atomic R-matrix Code (DARC) of Norrington and Grant. All partial waves with J less than or equal to 40.5 have been included, and the contribution of higher partial waves has been added to ensure the convergence of collision strengths for all transitions and at all energies. The results are compared with those available in the literature, and the accuracy of the data is assessed.

Excitation rate coefficients for transitions from the ground level of Gd XXXVII

Excitation rate coefficients, for transitions from the ground level to excited levels of Gd XXXVII, have been calculated over the temperature range 5002500 eV using the R-matrix method. It is observed that the contribution of resonances enhances the rates by up to an order of magnitude over the available (non- resonant) results of Hagelstein.

Electron impact excitation of A1 XIII: A relativistic approach

Energy levels, radiative rates, collision strengths, and effective collision strengths for all transitions up to and including the n = 5 levels of AlXIII have been computed in the j j coupling scheme including relativistic effects. All partial waves with angular momentum J less than or equal to 60 have been included, and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths are tabulated at energies above thresholds in the range 170.0 less than or equal to E less than or equal to 300.0 Ryd, and results for effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are tabulated over a wide temperature range of 4.4 less than or equal to log T-e less than or equal to 6.8 K. The importance of including relativistic effects in a calculation is discussed in comparison with the earlier available non-relativistic results.

Electron impact excitation of Al XIII: Collision strengths and rate coefficients

Collision strengths for all transitions up to and including the n = 5 levels of Al XIII have been computed in the LS coupling scheme using the R-matrix code. All partial waves with angular momentum L less than or equal to 45 have been included, and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths are tabulated at energies above thresholds in the range 162.30 less than or equal to E less than or equal to 220.0 Ry, and results for the 1s-2s and 1s-2p transitions are compared with those of previous authors. Additionally, effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are tabulated over a wide temperature range of 4.40 less than or equal to log T-e less than or equal to 6.40 K.

Electron impact excitation of Gd XXXVII and radiative rates for Ni-like ions with 60

Energy levels and radiative rates for transitions among the 107 finestructure levels belonging to the (1s(2)2s(2)2p(6)) 3s(2)3p(6)3d(10), 3s(2)3p(6)3d(9)4l, 3s(2)3p(5)3d(10)4l, and 3s3p(6)3d(10)4l configurations of Ni-like ions with 60 less than or equal to Z less than or equal to 90 have been calculated using the GRASP code. The collision strengths (Omega) have also been computed for transitions in Gd XXXVII at energies below 800 Ryd, using the DARC code. Resonances have been resolved in a fine energy mesh in the threshold region, and excitation rate coefficients have been calculated for transitions from the ground level to excited levels at temperatures below 2500 eV. These have been compared with those available in the literature, and enhancement in the values of rates, due to resonances, has been observed up to an order of magnitude for some of the transitions.

Effective collision strengths for electron impact excitation of C1III

Effective collision strengths for electron-impact excitation of the phosphorus-like ion Cl III are presented for all fine- structure transitions among the levels arising from the lowest 23 LS states. The collisional cross sections are computed in the multichannel close-coupling R-matrix approximation, where sophisticated configuration-interaction wave functions are used to represent the target states. The 23 LS states are formed from the basis configurations 3s(2)3p(3). 3s3p(4). 3s(2)3p(2)3d, and 3s(2)3p(2)4s, and correspond to 49 fine- structure levels, leading to a total possible 1176 fine- structure transitions. The effective collision strengths. obtained by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. are tabulated in this paper for all 1176 transitions and for electron temperatures in the ranges T(K) = 7500-25.000 and log T(K) = 4.4-5.3. The former range encompasses the temperatures of particular importance for application to gaseous nebulae. while the latter range is more applicable to the study of solar and laboratory-type plasmas. (C) 2001 Academic Press.

Effective collision strengths for electron impact excitation of Si VIII

Effective collision strengths for electron-impact excitation of the nitrogen-like ion Si VIII are presented over the wide range of electron temperatures log T(K) = 4.0-6.5. All 231 fine- structure transitions among the 22 fine-structure levels arising from the lowest 11 LS target states (2s(2)2p(3), 2s2p(4), 2p(5), and 2s(2)2p(2)3s) are considered in the tabulation. The collision strengths are evaluated in a multi- channel R-matrix approach, and the corresponding effective collision strengths are obtained by averaging these over a Maxwellian distribution of electron velocities. Comparisons are made with recent distorted-wave results at high incident electron energies. Differences of up to 20% are found, particularly for some allowed transitions. (C) 2003 Elsevier Inc. All rights reserved.

Electron impact excitation of Fe XVI: radiative and excitation rates

Aims. In this paper we report calculations for energy levels, radiative rates, collision strengths, and effective collision strengths for transitions in Fe XVI. Methods. For energy levels and radiative rates we have used the General purpose Relativistic Atomic Structure Package ( grasp), and for the compuations of collision strengths the Dirac Atomic R-matrix Code (darc) has been adopted. Results. Energies for the lowest 39 levels among the n