The CASPT2 calculations employed a IP-EA level-shift of 0.25 hartree. The electric field (and gradient) was evaluated using the "FLDG = 0" keyword in OpenMolcas. The electric field was evaluated for each state, where the plots in Figures 3 to 7 are for the ground and excited state properties versus ground-state electric field only. The electric field includes the effects of the electronic charge density shifts of the 87 Rb atom due to the interactions with the cell coating molecules. Spin-orbit coupling (SOC) was described using the RASSI program within OpenMolcas to compute the spin-orbit coupled states using single-state (SS) CASPT2 energies for the spin-free effective Hamiltonian's diagonal elements.