Fourier transform infrared study of sulfur dioxide dimer. II. Argon matrix Original Research Article

Fourier Transform infrared spectroscopy has been used to study sulfur dioxide isolated at different concentrations in solid argon. Results obtained for various isotopic species of SO2 are reported and discussed. The most stable (SO2)2 dimer in argon matrix is characterized by one ν3 absorption, and possesses a structure with the transition dipole moments of both subunits parallel or antiparallel one to another. Furthermore high resolution allowed to observe in the S16O18O vibrational region additional splittings leading to the conclusion that the four SO oscillators are not equivalent. A force field calculation on the dimer was performed. A good fit was obtained between calculated and observed ν3 frequencies for all dimer isotopic species. The suggested structure of the dimer in argon (Ci symmetry) which appears very different of that one observed in nitrogen matrix could be more realistic with respect to gas phase because the dynamic coupling between dimers and the lattice vibration are less important in argon than in nitrogen matrix.