Solvent-enabled photodissociation of CO2- in water clusters

The photofragmentation of CO2-(H2O)m, m = 3–20 at 355 nm yields two types of anionic products: O − (H 2 O) m−k, 1 ⩽ k ⩽ 3, and CO2-(H2O)m-k, 4 ⩽ k ⩽ 9, depending on the parent cluster size. The O − (H 2 O) m−k fragments, attributed to the dissociation of hydrated CO2-, are dominant for m = 3–7, while the water-evaporation products, CO2-(H2O)m-k, take precedence for m = 8–20. The dissociation of CO2- is proposed to proceed via a hydration-stabilized excited state, originating from a low-lying CO2- resonance. In the evaporation channel, the suggested routes include cluster predissociation, CO2- photodissociation/recombination, and charge transfer to solvent.