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

Abstract Vapor species of methanesulfonic acid (MSA, CH 3 SO 2 OH) trapped in solid Ar and Ar/H 2 O 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$H 2 O complex. Assignments are discussed in relation to MP2 and DFT calculations of vibrational frequencies. A single structure is suggested for the monomer whereas two structures of slightly different stabilization energies are suggested for both the dimer and the 1:1 MSA$H 2 O complex.