Non-Relativistic Calculation of Excited-State Ionization Potentials for Li-Like Ions Using Weakest Bound Electron Potential Model Theory

In this study, a well-known Weakest Bound Electron Potential Model (WBEPM) was used to determine the exited-state ionization potential of lithium-like elements for different iso-spectrum series such as 1s2 2p1  P1/2, 1s2 3s2  S1/2 , 1s2 3d2  D1/2, 1s2 4s2  S1/2, 1s2 4p2  P1/2,  and 1s2 4d2  D1/2 having nuclear charges from Z = 3 to Z = 18. On the other hand, to utilize relativistic correction, Briet-Pauli approximation has also been applied to the ionization potential using a fourth-order polynomial expression in the nuclear charge Z. The deviation within the range of 0.1% has been observed between estimated and experimental values that are quite remarkable. Furthermore, new ionization potentials were proposed for iso-series with Z ranging from 19 to 30.