Electron Impact Excitation of Ti XVIII

Abstract

Abstract Two different methods were used to calculate the collision strengths of boron-like titanium. One was a close-coupling way using the Dirac Atomic $R$-matrix Code (DARC) of P. H. Norrington and I. P. Grant (private communication), and the other was based on a relativistic distorted-wave (RDW) approximation with a Flexible Atomic Code (FAC) by Gu (2003). For DARC, the lowest 125 fine-structure levels belonging to the ($1s^{2}$) $2s^{2}2p, 2s2p^{2}, 2p^{3}, 2s^{2}3l, 2s2p3l$, and $2p^{2}3l$ ($l=s, p$, and $d$) configurations were included in the calculations. The target model space encompassed the lowest 15 levels, and all $105 \Delta n=0$ transitions together with 40 partial waves were included in calculations of the collision strengths. For FAC, the configuration interactions included in the calculations of atomic structure and excitation were among the same configurations of DARC. The collision strengths for all 125 levels were calculated at 10 scattered electron energies (10–10000 eV). The effective collision strengths, obtained after integrating the collision strengths of two codes over a Maxwellian distribution of electron energies, were also calculated for the electron temperatures in the range (50–500 eV). For application to spectral modeling or diagnostics, we report a complete set of data for the energy levels, radiative rates, and effective collision strengths (only FAC) for all transitions.