Detailed theoretical (Part I, this article) and experimental (Part II) investigations are presented for the mechanism of the atmospheric photooxidation of dimethyl sulfide (CH
3SCH
3) and dimethyl disulfide (CH
3SSCH
3). In this paper, comprehensive mechanisms for the atmospheric chemistry of CH
3SCH
3 and CH
3SSCH
3 are developed based on fundamental considerations of all available kinetic and mechanistic information.
Key words Dimethyl sulfide - dimethyl disulfide - photooxidation mechanism