Infrared spectrum and ab initio calculations of matrix isolated methanesulfonic acid species and its 1:1 water complex

Vapor species of methanesulfonic acid (MSA, CH3SO2OH) trapped in solid Ar and Ar/H2O matrices were investigated by FTIR spectroscopy. Intensity variations induced by matrix annealing and variations in water content indicate band assignments to monomeric and dimeric MSA species and to the 1:1 MSA·H2O complex. Assignments are discussed in relation to MP2 and DFT calculations of vibrational frequencies. A single structure is suggested for the monomer whereas two structures of slightly different stabilization energies are suggested for both the dimer and the 1:1 MSA·H2O complex.