Carbonyl sulfide isotopologues: Ultraviolet absorption cross sections and stratospheric photolysis

Ultraviolet absorption cross sections of the main and substituted carbonyl sulfide isotopologues were calculated using wavepacket dynamics. The calculated absorption cross section of (OCS)-O-16-C-12-S-32 is in very good agreement with the accepted experimental spectrum between 190 and 250 nm. Relative to (OCS)-O-16-C-12-S-32, isotopic substitution shows a significant enhancement of the cross section for (OCS)-O-16-C-13-S-32, a significant reduction for (OCS)-O-18-C-12-S-32 and (OCS)-O-17-C-12-S-32 and almost no change for the sulfur isotopologues (OCS)-O-16-C-12-S-33, (OCS)-O-16-C-12-S-34, and (OCS)-O-16-C-12-S-36. The analysis of the initial wavepackets shows that these changes can be explained in terms of the change in the norm of the initial wavepacket. Implications for our understanding of the stratospheric sulfur cycle are discussed. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3156314]