The Influence of Isotopic Substitution on the Expansion Parameters of an Effective Dipole Moment in Molecules of XY₂/XYZ Type

Abstract: Specific features of changes of molecular dipole characteristics upon isotopic substitution are discussed. On the basis of the operator perturbation theory and the group theory, analytic expressions are obtained for the first time for six expansion parameters of an effective dipole moment (^ai µ1, ^ai µ4, ^ai µ5, ^ai µ9, ^ai µ12, and ^ai µ14) in the case of the nonsymmetric substitution XYZ ← XY₂. The expressions that yield relationship between the equilibrium dipole moment and the first dipole moment derivatives of a “parent” molecule and an isotopically substituted molecule are obtained. For the example of the ³²S¹⁶O₂, ³⁴S¹⁶O₂, ³²S¹⁸O₂, and ³²S¹⁶O¹⁸O molecules, the parameters of an effective dipole moment are numerically calculated.