Study of fragmentation dynamics for CO2q+ (q≤4) in strong laser fields

BackgroundThe research of molecular fragmentation dynamics has attracted extensive attention in the fields of physics, chemistry and biology. The major challenge in this field is to understand the selectivity of molecular bond breaking and to elucidate which parameters control bond fission.PurposeThis study aims to reveal the mechanism of two and three-body fragmentation of CO2 in strong laser fields and to elucidate the dynamics information of the ion fragmentation in the Coulomb explosion.MethodsThe time-of-flight (TOF) and three-dimensional momentum distributions of ion fragments were obtained using a cold-target recoil ion momentum spectroscopy (COLTRIMS). Precise identification of the two-body and three-body dissociation channels of CO2 was determined by the photoion-photoion coincidence (PIPICO) and the photoion-photoion-photoion coincidence (PIPIPICO) techniques. The occurrence of sequential and non-sequential fragmentation during three-body dissociation was revealed by the momentum correlation between two O ions. Finally, the dynamics of the three-body fragmentation process was visualized by the Newton diagram.ResultsFour two-body dissociation channels and three three-body dissociation channels for CO2q+ (q≤4) are identified with the coincidence technique. The kinetic energy release (KER) distribution of these dissociation channels is obtained from the three-dimensional momentum.ConclusionsThe experiments reveal that the dynamic collimation mechanism plays a dominant role in the two-body fragmentation channels, and the ion fragments of the four two-body fragmentation channels are mainly emitted along the laser polarization direction with the significant anisotropic distribution. Non-sequential and sequential fragmentation of CO2 is separated and identified in the momentum correlation and Newtonian diagrams. In the first step of the sequential fragmentation of CO24+, the O2+ and CO2+ ionic fragments are always produced. It is further shown that the vibration and rotation of the CO2+ ion are shown to occur before the fragmentation of the second step.