Direct production of molecular oxygen from carbon dioxide and helium ion collisions.

The prebiotic mechanism to produce molecular oxygen (O 2 ) in carbon dioxide (CO 2 )-rich planetary atmospheres is of great importance in understanding astrochemical reactions and is potentially relevant to the origin of life on Earth. Here, we demonstrate that, aside from the direct productions of O 2 by photodissociation and dissociative electron attachment, the low-energy ion-molecule reaction between cationic helium in solar winds and molecular CO 2 is a noticeable mechanism. Branching ratios of the reaction channels are determined, and their absolute cross-sections are estimated accordingly. The present findings represent a further, indispensable step towards fully understanding the origins of atmospheric O 2 .