Paper XXVII

Electron impact excitation collision strengths and rate coefficients for Fe IV

H.L. Zhang and A.K. Pradhan

Astronomy & Astrophysics Supplement Series, 1997, Vol.126, pp.373-378

Collision strengths and maxwellian-averaged rate coefficients have been calculated for 8771 non-vanishing transitions among 140 fine structure levels, dominated by the configurations 3d$^5$, 3d$^4$4s and 3d$^4$4p in Fe IV. Collision strengths are calculated using the R-matrix method with a 49 term close-coupling target expansion for electron energies up to 15 rydbergs. Rate coefficients are tabulated for a wide range of temperatures in which Fe IV is abundant in plasma sources. A brief discussion of the calculations and sample results are given. The present rates for Fe IV are expected to find applications in spectral diagnostics of a variety of astrophysical sources.