The primary photo-dissociation dynamics of lactic acid: decarboxylation as CO 2 and CO 2 ˙ .

We study the primary photolysis dynamics of lactic acid induced by excitation at λ = 200 nm with the aim of elucidating how simple aqueous carboxyl acids react to the deep ultraviolet exposure on the prebiotic Earth. UV-IR transient absorption spectroscopy shows a photolysis quantum yield of Φ (100 ps) = 100 ± 5%. The primary products are CO 2 , CO 2 ˙ - and their counter products CH 3 CHOH˙ and CH 3 CHOH - . DFT calculations suggest that the dissociation takes place from the strongly acidic nπ* excited state. Dehydroxylation of lactic acid is not observed.