Microwave Spectrum of the N2O−SO2Dimer: Evidence for Tunneling and an Asymmetric Structure

Abstract

The microwave spectrum of the nitrous oxide−sulfur dioxide complex has been investigated. The dimer differs from similar complexes of SO2 with a linear molecule in that it lacks a symmetry plane. A tunneling motion splits the transitions into doublets. This is attributed to an interconversion between mirror-image conformations in which the oxygen atoms on the SO2 are inequivalent. The rotational constants for the normal species are A = 6126.9781(15) MHz, B = 1494.537(37) MHz, and C = 1435.474(36) MHz for the higher frequency component of the doublets and A = 5500 MHz (fixed), B = 1463.483(23) MHz, and C = 1420.953(23) MHz for the lower frequency component. Spectra for four isotopomers in addition to the normal species have been measured, and the dipole moment of the complex has been determined to be 1.212 D. A semiempirical model with atom−atom interaction terms is consistent with an asymmetric equilibrium structure.