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The absorption spectrum of O2 and O2‐O2 collision pairs were measured over the wavelength range from 330 to 1140 nm using pressures of O2 from 1 to 55 atm at 298 K. Absorption cross sections, pressure dependences, band centers, and full widths at half maximum of the observed absorption bands centered at 343.4, 360.5, 380.2, 446.7, 477.3, 532.2, 577.2, 630.0, 688, 762, and 1065.2 nm are reported. The absorption bands centered at 360.5, 380.2, and 477.3 nm were also measured at 196 K and their temperature dependences were characterized.

Dimethyl sulfide (DMS), emitted from the oceans, is the most abundant biological source of sulfur to the marine atmosphere. Atmospheric DMS is oxidized to condensable products that form secondary aerosols that affect Earth’s radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report the atmospheric discovery of a previously unquantified DMS oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations that demonstrate it to be a major reservoir of marine sulfur. Observationally constrained model results show that more than 30% of oceanic DMS emitted to the atmosphere forms HPMTF. Coincident particle measurements suggest a strong link between HPMTF concentration and new particle formation and growth. Analyses of these observations show that HPMTF chemistry must be included in atmospheric models to improve representation of key linkages between the biogeochemistry of the ocean, marine aerosol formation and growth, and their combined effects on climate.