Dynamics of three-particle fragmentation of (CO2)23+ ions produced by intense femtosecond laser fields

In a momentum coincidence measurement experiment, we studied the three-body fragmentation dynamics of carbon dioxide dimers in intense femtosecond laser fields. The three-dimensional momentum vectors and kinetic energies of the fragments were recorded in a cold-target recoil-ion momentum spectrometer. An analysis shows that ${({\mathrm{CO}}_{2})}_{2}{}^{3+}$ breaks up into ${\mathrm{CO}}_{2}{}^{+}+{\mathrm{CO}}^{+}+{\mathrm{O}}^{+}$ ions through both concerted and sequential fragmentation channels. These two fragmentation channels are consistent with the instantaneous and metastable dissociation channels in the dissociation dynamics of ${\mathrm{CO}}_{2}{}^{2+}$ ion breakup into ${\mathrm{CO}}^{+}$ and ${\mathrm{O}}^{+}$ ions. From Coulomb explosion imaging, our results show that, for the parallel sliding structure of the carbon dioxide dimer molecules, the angle between the C=O bond and the van der Waals bond is $48{}^{\ensuremath{\circ}}$, and the intermolecular nuclear distance $R({\mathrm{CO}}_{2}\text{\ensuremath{-}}{\mathrm{CO}}_{2})$ is 4.0 \AA{}. By tracing the direction of the fragmentation ions, the ${\mathrm{O}}^{+}$ was found to be produced from the C=O bond that is closer to the center of the C-C bond during direct dissociation. These results indicate that the dynamic characteristics of the monomer is retained and gives rise to new dynamics in the molecular cluster complexes. Finally, we have measured angular distributions of ion fragments produced by different dissociation channels of ${({\mathrm{CO}}_{2})}_{2}$, and the results reveal that the structure of the dimer and its relative orientation in the laser field govern the ionization dynamics.