H d in the above equation ( ) is known as the effective Hamiltonian for the eEDM interaction, which is defined as 2icd e γ 0 γ 5 p 2 ; where γ 0 and γ 5 are the usual Dirac matrices, p is the momentum operator, c is the speed of light and i = √ -1. The molecular electronic structure parameter for the scalar-pseudoscalar (S-PS) nucleon-electron interaction, W S reads as