Ultrafast Pump-probe Photodissociation Dynamics Of Co₂ For The Production Of Molecular Oxygen

Molecules excited by strong-field laser pulses evolve through coupled nuclear and electronic motion over ultrafast timescales. Even simple molecules demonstrate a variety of characteristic dynamics, including vibrations, fragmentation, and ionization. The final products and their relative yields depend sensitively on details of these coupled processes that occur within the first few femtoseconds of interacting with the laser beam. Here, ultrafast pump-probe spectroscopy is applied to study the fragmentation and ionization dynamics of several molecules. Photodissociation of CO$_{2}$ proceeds via multiple pathways depending on available energy, but commonly into CO and O. Multiphoton excitation from a 35 fs pump laser impulsively transfers CO$_{2}$ from the ground to 1st excited 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 O$_{2}$$^{+}$ fragments. The state relaxes to the ground state through a conical intersection. Similar control over the fragmentation pathway and ion yields will be demonstrated for the excited state motions of ethanol and formic acid