Aims. Transition probabilities and electron impact excitation collision strengths and rates for astrophysically important lines in Mg V are reported. The 86 fine-structure levels of the 2s 2 2p 4 , 2s2p 5 , 2p 6 , 2s 2 2p 3 3s, 2s 2 2p 3 3p and 2s 2 2p 3 3d configurations are included in our calculations. The effective collision strengths are presented as a function of electron temperature for solar and other astrophysical applications.Methods. The collision strengths have been calculated using the B-spline Breit-Pauli R-matrix method for all fine-structure transitions among the 86 levels. The one-body mass, Darwin and spin-orbit relativistic effects are included in the Breit-Pauli Hamiltonian in the scattering calculations. The one-body and two-body relativistic operators are included in the multiconfiguration Hartree-Fock calculations of transition probabilities. Several sets of non-orthogonal spectroscopic and correlation radial orbitals are used to obtain accurate description of Mg V 86 levels and to represent the scattering functions. Results. The calculated excitation energies are in very good agreement with experiment and represents an improvement over the previous calculations. The present collision strengths show good agreement with the previously available R-matrix and distorted-wave calculations. The oscillator strengths for E1 transitions normally compare very well with previous calculations. The thermally averaged collision strengths are obtained by integrating total resonant and non-resonant collision strengths over a Maxwellian distribution of electron energies and these are presented over the temperature range log 10 T e = 3.2−6.0 K.

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Electron excitation collision strengths for a wide range of transitions giving rise to infrared, optical, ultraviolet, and extreme ultraviolet lines of S iii have been calculated using the B-spline Breit–Pauli R-matrix method. The term-dependent non-orthogonal orbitals have been employed for the accurate representation of target wave functions and the electron plus S iii target scattering system. The multiconfiguration Hartree–Fock method has been utilized for the calculation of 198 S iii fine-structure level energies belonging to the , , , and 3s3p 25s configurations. The transition probabilities between fine-structure levels have also been calculated and compared with available other calculations. The close-coupling expansion includes these 198 fine-structure levels of S iii in the electron collision calculations. The effective collision strengths are calculated at electron temperatures in the range of 103–106 K for all possible transitions between the 198 fine-structure levels. The present calculation includes a larger number of levels in the close-coupling expansion and improved target description than previous calculations and should be useful for the analysis of measured spectra from various astrophysical objects. Comparison with other calculations is used to assess likely uncertainties in the existing collision and radiative rates for S iii. The collision and radiative rates are estimated to be accurate to about 20% or better for most main transitions of astrophysical importance.

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