UV light irradiation of dimethyl sulfoxide (DMSO) in low temperature solid argon matrix produces sulfenic ester, CH3SOCH3, a high energy structural isomer of DMSO. The sulfenic ester molecule further dissociates to the CH2O-CH3SH complex under 266 nm laser irradiation. The CH2S-CH3OH complex is also formed upon UV light irradiation. The infrared spectra-of the aforementioned species are assigned on the basis of isotopic substitutions (C-13 and deuterium) as well as density functional frequency calculations.