For isolated 87 Rb atom the energy splitting of the 5 2 P 1/2 and 5 2 P 3/2 J levels is calculated to be 0.018 eV using SS-CASPT2/TZP energies in the computation of SOC. The experimental splitting is 0.029 eV. Thus, it is judicious to assess the impact of SOC on the energy shifts and transition energies discussed above. MeTS and ethene giving a negative energy shift. The SOC 2 2 A and 3 2 A states of 87 Rb all undergo negative shifts with slightly different magnitudes compared to the non-SOC 2