Ultraviolet photoabsorption in the B 3Σ- − X 3Σ- and C 3Π − X 3Σ- band systems of SO sulphur isotopologues

Abstract

High-resolution far-ultraviolet broadband Fourier-transform photoabsorption spectra of 32S16O, 33S16O, 34S16O, and 36S16O are recorded in a microwave discharge seeded with SO2. The (Formula presented.) and (Formula presented.) bands are observed or inferred in the (Formula presented.) –51,000 cm−1 (196 to 233 nm) spectral range. This is the first experimental detection of a (Formula presented.) level and of any of these observed bands in an S-substituted isotopologue. Additional measurements of (Formula presented.) provide a calibration of the SO column density. Measured band profiles are fitted to an effective-Hamiltonian model of coupled excited B 3Σ− and C 3Π states along with their predissociation linewidths and absorption band strengths. Electronic-state potential-energy curves and transition moments are deduced. The end result is a list of line frequencies, f-values, and dissociation widths describing the far-ultraviolet photodissociation spectrum of SO that is accurate enough for computing atmospheric photolytic isotope-fractionation. Linelists, and photoabsorption and photodissociation cross sections are available as supplementary data.