\begin{document}${\rm{(CO_2)}}_{2}^{4+}$\end{document} 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 \begin{document}${\rm{(CO_2)_2}}$\end{document} 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 \begin{document}${\rm{8 \times10^{14}}}\;{\rm{W/cm^2}}$\end{document} are produced by a femtosecond Ti:sapphire multipass amplification system. We concentrate on the three-particle breakup channel \begin{document}${\rm{(CO_2)_2^{4+}}} \rightarrow {\rm{CO}}_{2}^{2+}+{\rm{CO^+}}+ {\rm{O^+}}$\end{document}. The two-particle breakup channels, \begin{document}${\rm{(CO_2)_2^{4+}}} \rightarrow {\rm{CO}}_{2}^{2+}+ {\rm{CO_{2}}^{2+}}$\end{document} and \begin{document}${\rm{CO_2^{2+}}\rightarrow CO^++O^+}$\end{document}, 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 \begin{document}${\rm{(CO_2)}}_{2}^{4+}$\end{document} ions break into \begin{document}${\rm{CO}}_{2}^{2+}+{\rm{CO}}^++{\rm{O}}^+$\end{document} 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, \begin{document}${\rm{(CO_2)}}_{2}^{4+}$\end{document} dissociates into two \begin{document}${\rm{CO}}_{2}^{2+}$\end{document} ions; and then one of the C=O covalent bonds of \begin{document}${\rm{CO}}_{2}^{2+}$\end{document} breaks up, the \begin{document}${\rm{CO}}_{2}^{2+}$\end{document} ion breaks into \begin{document}${\rm{CO^+}}$\end{document} and \begin{document}${\rm{O^+}}$\end{document}. The time interval between the two steps is longer than the rotational period of the intermediate \begin{document}${\rm{CO}}_{2}^{2+}$\end{document} 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 \begin{document}${\rm{(CO_2)}}_{2}^{4+}$\end{document} ions in comparison of the event ratio of the two fragmentation channels."> - 必威体育下载

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Zeng Ping, Song Pan, Wang Xiao-Wei, Zhao Jing, Zhang Dong-Wen, Yuan Jian-Min, Zhao Zeng-Xiu
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  • Received Date:29 April 2023
  • Accepted Date:23 May 2023
  • Available Online:06 June 2023
  • Published Online:20 September 2023

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