Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Fe VIII. The configurations used are 3 p 6 3d, 3p 5 3d 2 , 3p 6 4s, 3p 6 4p, and 3 p 5 3d4s giving rise to 73 fine-structure levels in intermediate coupling. Collision strengths are calculated at four incident energies, 10, 30, 50, and 70 Ry. Excitation rate coefficients are calculated by assuming a Maxwellian electron velocity distribution at an electron temperature of log T e (K) = 5.57, corresponding to maximum abundance of Fe VIII. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities 10 8 -10 14 cm −3 . Relative spectral line intensities are calculated. Proton excitation rates and solar blackbody radiative excitation are also included in the statistical equilibrium equations. C [2,3]. The same set of lines has also been observed by Malinovsky and Heroux [4], who measured the spectra photoelectrically using a double spectrometer flown on an Aerobee rocket. The 185.221Å line has been observed from the SERTS-95 flight [5] but it is blended with the Ni XVI line at 185.231Å. The same line has also been observed with the RES-K spectroheliograph on board the KORONAS-I satellite [6]. There are a number of unidentified lines in the recent compilation of lines observed from the UV spectrometer SUMER on SOHO [7] and it is suspected that some of these lines could be Fe VIII lines. Accurate atomic data for this ion must be available for identification of various spectral lines and to infer properties of solar and astrophysical plasmas. The presently calculated data will be useful for any present and future observations.In order to interpret data from these missions, atomic data such as energy levels, oscillator strengths, radiative transition rates, and collision strengths are required. provides all the quantities required for diagnostic purposes. In this paper we carry out a distorted wave calculation for Fe VIII in the same way as for the other Fe ions mentioned above. Since coupling between various channels is not included in the distorted wave approximation, the present calculation does not include resonances which could be important for forbidden transitions but usually not for dipole-allowed transitions for which most of the contribution to collision strengths comes from a very large number of incident partial waves.We present energy levels, oscillator strengths, radiative transition rates, and collision strengths for Fe VIII for 73 finestructure levels obtained by using the configurations 3 p 6 3d, 3 p 5 3d 2 , 3p 6 4s, 3p 6 4p, and 3 p 5 3d4s, above the Mg-like 1s 2 2s 2 2 p 6 3s 2 core. Although Fe VIII is K-like, the outermost electron is in the 3d orbital, not in the 4s orbital as in neutral potassium. Therefore, the lowest configuration is 3 p 6 3d. We solve the statistical equilibrium equations for level populations at log T e (K) = 5.57 where T e is the temperature of...
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