High-precision spectroscopy of 32S, 33S, and 34S sulfur dioxide:: Ultraviolet absorption cross sections and isotope effects

We report measurements of the ultraviolet absorption cross sections of (SO2)-S-32, (SO2)-S-33, and (SO2)-S-34, recorded from 30,300 to 52,500 cm(-1) ( 330 to 190 nm) at 293 K with a resolution of 25 cm(-1). The (SO2)-S-33 sample was produced by the combustion of isotopically enriched S-33 while the (SO2)-S-34 and natural abundance samples were obtained from commercial manufacturers. The spectrum of the natural abundance sample is in agreement with previously published spectra. The spectra of the isotopically pure species were retrieved using the isotopic composition of the samples. The (SO2)-S-32, (SO2)-S-33, and (SO2)-S-34 absorption spectra show rich vibrational structure, and the positions and widths of the peaks change with isotopic substitution in a complex fashion. The results imply that large wavelength-dependent and broadband isotopic fractionations are associated with the UV photolysis of SO2.