ELECTRON-IMPACT COLLISION STRENGTHS FOR NEUTRAL FLUORINE

Configuration-interaction wave functions are constructed for the lowest 11 atomic target states of neutral fluorine. These wave functions are used to calculate target-state energies and absorption oscillator strengths for the dipole-allowed transitions. In general, a good agreement is found between the length and velocity forms of f values. However, f values for some transitions show significant discrepancies between these two forms. All these target states are retained in the R-matrix basis function and the (N + 1)-electron collision wave functions are expanded in terms of these basis functions. The calculations are performed for the electron-impact excitation collision strengths for all transitions between these states using the R-matrix method. In the low-partial-wave region (total angular momentum L less-than-or-equal-to 12) the full exchange R-matrix method is employed while a no-exchange R-matrix method is used for the calculations in the partial-wave region with 13 less-than-or-equal-to L less-than-or-equal-to 40. The effect of this procedure is most evident in the case of dipole-forbidden transitions for which collision strengths increase by about 10-60 % due to the contribution from higher partial waves. Beyond this value of the total angular momentum, the Burgess sum rule is applied to determine the higher partial-wave contribution to the total collision strengths for dipole-allowed transitions. The collision strengths are obtained for a wide range of incident electron energy from the first excitation threshold to 3.0 Ry. The calculations are performed in the LS-coupling scheme.