We study experimentally the three-body Coulomb explosion dynamics of carbon dioxide dimer
${\rm{(CO_2)}}_{2}^{4+}$
ions produced by intense femtosecond laser field. The three-dimensional momentum vectors as well as kinetic energy are measured for the correlated fragmental ions in a cold-target recoil-ion momentum spectrometer (COLTRIMS). Carbon dioxide dimer is produced during the supersonic expansion of
${\rm{(CO_2)_2}}$
gas from a 30 μm nozzle with 10 bar backing pressure. The linearly polarized laser pulses with a pulse duration (full width at half maximum of the peak intensity) of 25 fs, a central wavelength of 790 nm, a repetition rate of 10 kHz, and peak laser intensities on the order of
${\rm{8 \times10^{14}}}\;{\rm{W/cm^2}}$
are produced by a femtosecond Ti:sapphire multipass amplification system. We concentrate on the three-particle breakup channel
${\rm{(CO_2)_2^{4+}}} \rightarrow {\rm{CO}}_{2}^{2+}+{\rm{CO^+}}+ {\rm{O^+}}$
. The two-particle breakup channels,
${\rm{(CO_2)_2^{4+}}} \rightarrow {\rm{CO}}_{2}^{2+}+ {\rm{CO_{2}}^{2+}}$
and
${\rm{CO_2^{2+}}\rightarrow CO^++O^+}$
, are selected as well for reference. The fragmental ions are guided by a homogenous electric field of 60 V/cm toward microchannel plates position-sensitive detector. The time of flight (TOF) and position of the fragmental ions are recorded to reconstruct their three-dimensional momenta. By designing some constraints to filter the experimental data, we select the data from different dissociative channels. The results demonstrate that the three-body Coulomb explosion of
${\rm{(CO_2)}}_{2}^{4+}$
ions break into
${\rm{CO}}_{2}^{2+}+{\rm{CO}}^++{\rm{O}}^+$
through two mechanisms: sequential fragmentation and non-sequential fragmentation, in which the sequential fragmentation channel is dominant. These three fragmental ions are produced almost instantaneously in a single dynamic process for the non-sequential fragmentation channel but stepwise for the sequential fragmentation. In the first step, the weak van der Waals bond breaks,
${\rm{(CO_2)}}_{2}^{4+}$
dissociates into two
${\rm{CO}}_{2}^{2+}$
ions; and then one of the C=O covalent bonds of
${\rm{CO}}_{2}^{2+}$
breaks up, the
${\rm{CO}}_{2}^{2+}$
ion breaks into
${\rm{CO^+}}$
and
${\rm{O^+}}$
. The time interval between the two steps is longer than the rotational period of the intermediate
${\rm{CO}}_{2}^{2+}$
ions, which is demonstrated by the circle structure exhibited in the Newton diagram. We find that the sequential fragmentation channel plays a dominant role in the three-body Coulomb explosion of
${\rm{(CO_2)}}_{2}^{4+}$
ions in comparison of the event ratio of the two fragmentation channels.
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