Evaluation of Electron Impact Excitation Data Along Isoelectronic Sequences

R-matrix calculations of electron impact excitations have been done for several isoelectronic sequences under the program of the Atomic Processes for Astrophysical Plasmas network in the United Kingdom. The intermediate-coupling framework transformation R-matrix approach was used to generate data in this program since it is less resource (time/memory) demanding than the full Breit-Pauli R-matrix method, without reduction of accuracy. A detailed accuracy assessment was done for four/five/six selected ions spanning the isoelectronic sequence, which provides insight into the behavior of the whole sequence of ions. For each ion, we adopted the following procedure: First, the target structure was assessed by comparing the calculated level energies with available experimental data and with previous calculations using different methods. Second, weighted oscillator strengths or line strengths or radiative decay rates were compared with various available theoretical works for several transitions. Usually, a "survey" comparison with another database has been done for all available transitions by way of a scatter plot. Finally, direct comparison for the excitation (effective) collision strength is done with available measurements or with previously published data. A survey comparison with another database is usually presented to investigate the spread of the consistency or inconsistency among the different calculations.