Production of O₂ from Ultrafast Pump-Probe CO₂ Photodissociation

Carbon dioxide (CO₂) is ubiquitous in our atmosphere and plays important roles in the life cycle, the greenhouse effect, and has potential applications in industrial processes as a chemical feedstock. Concern over the ever-increasing concentration of CO₂ in our environment has sparked a renewed interest in its photoabsorption dynamics. Photodissociation of CO₂ proceeds via multiple pathways depending on available energy, but commonly into CO and O. Here, ultrafast pump-probe spectroscopy is applied to study the excited state dynamics of CO₂. Multiphoton excitation from a 35 fs pump laser impulsively transfers CO₂ from the X → A state, preparing a bending vibrational wavepacket that influences its dissociation.Using mass spectrometry, we report changes in the fragmentation pattern as a function of time delay between the pump and probe laser pulses that reflect the vibrational motion. At well-defined time delays the dissociation oscillates between observable CO⁺and O₂⁺ fragments. The state relaxes to the ground state through a conical intersection.