Ultraviolet photoabsorption in the $B{}^3{\Sigma }^{-}-X{}^3{\Sigma }^{-}$ and $C{}^3\Pi -X{}^3{\Sigma }^{-}$ band systems of SO sulphur isotopologues

Abstract

High-resolution far-ultraviolet broadband Fourier-transform photoabsorption spectra of ${}^{32}{\mathrm{S}}^{16}\mathrm{O}$, ${}^{33}{\mathrm{S}}^{16}\mathrm{O}$, ${}^{34}{\mathrm{S}}^{16}\mathrm{O}$, and ${}^{36}{\mathrm{S}}^{16}\mathrm{O}$ are recorded in a microwave discharge seeded with SO${}_2$ . The $B{}^3{\Sigma }^{-}(v=4-30)\leftarrow X{}^3{\Sigma }^{-}(v=0)$ and $C{}^3\Pi (v=0-7)\leftarrow X{}^3{\Sigma }^{-}(v=0)$ bands are observed or inferred in the 43000 to 51000 cm${}^{-1}$ (196 to 233 nm) spectral range. This is the first experimental detection of a $C{}^3\Pi (v>2)$ level and of any of these observed bands in an S-substituted isotopologue. Additional measurements of $A{}^3\Pi (v=1-3)\leftarrow X{}^3{\Sigma }^{-}(v=0)$ provide a calibration of the SO column density. Measured band profiles are fitted to an effective-Hamiltonian model of coupled excited $B{}^3{\Sigma }^{-}$ and $C{}^3\Pi$ 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.

References in corpus (8)

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Cited by in corpus (2)

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