## 3 Results and Discussion
### The Dissociative Ionization of Molecule \(\rm{CF_{2}Br_{2}}\) in 800 nm Laser Fields
We shall abbreviate the residual amount of energy to \(\mathrm{E_{AV}}\) shown in Equation (4), and the total translational energy (\(\mathrm{E_{T}}\)) of the fragments can be obtained according to the following Equation (5):  
\[\mathrm{E_{AV}} =\mathrm{\ nhv}-\mathrm{E_{AP}} \tag{4}\] \[\mathrm{E_{T(AB)}} =\frac{\mathrm{m_{A}}+\mathrm{m_{B}}}{\mathrm{m_{B}}}\mathrm{E_{ K(A)}} \tag{5}\]  
where \(\mathrm{m_{A}}\) and \(\mathrm{m_{B}}\) represent the mass of reaction products A and B, respectively. Because part of the \(\mathrm{E_{AV}}\) is released to the internal energy of fragments, the \(\mathrm{E_{T}}\) of fragments for each channel should be smaller than \(\mathrm{E_{AV}}\). Here, the recoil momentum of the ionized electron is neglected and only the ion and neutral partner are calculated. The \(\mathrm{E_{K}}\), \(\mathrm{E_{T}}\) and \(\mathrm{E_{AV}}\) for the three different reaction channels are listed in Table 2. The experimental results are in good agreement with the calculated results, which demonstrates the above estimated channels originate from the dissociative ionization of molecule \(\mathrm{CF_{2}Br_{2}}\). The related dissociation channels of parent ions are shown in Figure 4 (red lines). The energy of the ground state of molecular \(\mathrm{CF_{2}Br_{2}}\) is defined as zero in order to simplify subsequent discussion. It is noted that the \(\mathrm{E_{AP}}\) of channel one is 11.19 eV; however, the \(\mathrm{E_{AP}}\) for channel two increases to 15.85 eV. The reason could be the difference in charge distribution after dissociation along the C-Br bond. Hence, we calculated the charge distribution between the above two channels. Figure 5 shows the natural bond orbital (NBO) charge distribution of ions \(\mathrm{CF_{2}Br_{2}}^{+}\) and the corresponding fragments. It is obvious that \(\mathrm{CF_{2}Br}\) and Br share out nearly the same in the charge distribution of parent ion \(\mathrm{CF_{2}Br_{2}}^{+}\). Once the C-Br bond is broken, either \(\mathrm{CF_{2}Br}\) or Br is likely to be ionic state. The ionization potential of \(\mathrm{CF_{2}Br}\) and Br are 8.4 and 13.1 eV \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Channel** & **\(\mathrm{E_{K}}\) (eV)** & **\(\mathrm{E_{T}}\) (eV)** & **\(\mathrm{E_{AV}}\) (eV)** \\ \hline (1) & 0.01 & 0.03 & 1.21 \\ (2) & 0.13 & 0.21 & 1.20 \\ (3) & 0.11 & 0.14 & 1.44 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The energy list for above estimated channels. Figure 4: Ab initio calculation of dissociation pathways of the singly charged \(\mathrm{CF_{2}Br_{2}}^{+}\) ions. (G4 level), respectively, which indicates that CF\({}_{2}\)Br more easily lose the electron to yield CF\({}_{2}\)Br\({}^{+}\) ion. Therefore, the corresponding ionization energies of these neutral parts play a crucial role in the related dissociative ionization channels. Comparing with the channel one, the ions CF\({}_{2}\)Br\({}_{2}\)\({}^{+}\) need to break two C-Br bonds to yield the CF\({}_{2}\)\({}^{+}\) ion according to the channel three. The relaxed force constants of the C-Br bond for CF\({}_{2}\)Br\({}^{+}\) and CF\({}_{2}\)Br\({}^{+}\) are 1.45 and 4.18 mdyn/A, respectively (See Supplementary Materials, Table S1 and Figure S3b). The second C-Br bond strength is enhanced after losing one Br atom, which results in the E\({}_{\rm{AP}}\) (15.61 eV) of channel three being much higher than that of channel one. The Special Dissociation Channels for Singly Ion CF\({}_{2}\)Br\({}_{2}\)\({}^{+}\) in 400 nm Laser Fields  
The elimination reaction only occurred in the 400 nm laser field. We have performed the related calculations to explore the dynamic process, and the results are shown in Figure 4 (blue lines). The elimination process can be separated into three stages. Briefly, the singly charged ions CF\({}_{2}\)Br\({}_{2}\)\({}^{+}\) overpasses the energy barrier of 1.7 eV to the transition state (TS\({}_{1}\)), and then transfers quickly into the transition state TS\({}_{2}\). Finally, the TS\({}_{2}\) transforms spontaneously to the intermediate state (IS).