Isotopic Shifts of Vibrational-Rotational Lines of SO₂

Simple isotopic relations between the energy levels of ³²S¹⁶O₂, ³³S¹⁶O₂, and ³⁴S¹⁶O₂ isotopologues and of other isotopic variants are applied to calculations of vibrational-rotational energy levels. To estimate the accuracy of these isotopic relations, we calculated line centers in the microwave spectrum of ³⁶S¹⁶O₂ isotopologue and compared them with measured ones. The comparison shows their quite satisfactory agreement at a level of 10⁻⁴ cm⁻¹. Vibrational-rotational energy levels of sulfur dioxide isotopologues ^XS¹⁶O₂, X = 35–38, are presented for five lower vibrational states up to J = 9.