The CASSCF active space comprises the 5s orbital and electron and the three 5p orbitals on 87 Rb and is denoted (1,4). This minimal active space is able to describe the ground state ( 2 S) and the three degenerate excited states (5 2 P) of 87 Rb. State-averaged CASSCF calculations for the four lowest-energy roots in C 1 symmetry were performed throughout this study.