Charge Resonance Enhanced Ionization of CO2 Probed by Laser Coulomb Explosion Imaging
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The process by which a molecule in an intense laser ?eld ionizes more ef?ciently as its bond length increases towards a critical distance Rc is known as charge resonance enhanced ionization (CREI). We make a series of measurements of this process for CO2 , by varying pulse duration from 7 to 200 fs, in order to identify the charge states and time scales involved. We ?nd that for the 4 nd higher charge states, 100 fs is the time scale required to reach the critical geometry hRCO i ?? 2:1 ?? A and h??OCO i ?? 163?? (equilibrium CO2 geometry is hRCO i ?? 1:16 ?? A and h??OCO i ?? 172?? ). The CO2 3 olecule, however, appears always to begin dissociation from closer than 1.7 Aࠩndicating that dynamics on charge states lower than 3 s not suf?cient to initiate CREI. Finally, we make quantum ab initio calculations of ionization rates for CO2 and identify the electronic states responsible for CREI.
Physical Review Letters
Atomic and Molecular Physics