## 4 Discussion
The remaining columns indicate the R\({}_{\rm cr}\) calculated at various laser intensities. It is demonstrated that when the laser intensity rises, the R\({}_{\rm cr}\) decreases and the chance of CT rises. We are worried about whether each channel ionization and CT procedure can happen in order. Taking (1, 1)\(\rightarrow\)(2, 1)\(\leftrightarrow\)(1, 2) as an example, the ionization process occurs when the internuclear distance R\({}_{\rm(1,1)}\) is 4.22 A. But for the CT process, the maximum value of R\({}_{\rm cr}\) is 3.68 A within the experimental conditions. This means that when the stretched length of the internuclear distance exceeds 3.68 A, the CT process is prohibited from occurring. Therefore, once the charge state (2, 1) has been formed, it has no chance to undergo further charge transfer and form the charge state (1, 2). Other channels are similar. Hence, it is not reasonable for the ionization process to occur first and then for the charge transfer process to take place. Second, we consider the effects of the existence of the next higher process, i.e., ionization with two electrons. This is important because in the atom, the ionization rate of two electrons is usually low. However, in molecules, the ionization rate of two electrons appears to exceed the ionization rate of one electron under certain conditions. Based on the experimentally obtained channels, Table 4 considers all possible situations for the sequential ionization paths with one and two electrons. Based on the different CE channels, we also classify the above ionization paths into five categories, as shown in (f)-(j). In contrast to the one-electron sequential ionization process in Table 2, the two-electron sequential ionization process is distinguished by bolding. Taking process (f) as an example, the ionization path is (1, 1)\(\rightarrow\)(1, 2)\(\rightarrow\)(2, 2)\(\rightarrow\)(2, 3) \(\rightarrow\) (4, 3). The first three steps are single ionization processes, and the last step is a double ionization process. As predicted by the \"ladder-path\" model, this configuration fully guarantees that the internuclear distance at the subsequent ionization phase is always higher than the internuclear distance at the preceding step. The travel  
Figure 5: Double-well potential schematic diagrams for the outer electron of IB\({}^{(n+m)+}\) at three internuclear separations and under a constant external electric field: (a) at small R, (b) at intermediate R, and (c) at long-distance R, respectively. The black dashed line represents the electron energy level E\({}_{\rm L}\), while the red solid line represents the E\({}_{\rm L}\) with the additional Stark shift. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Channels**} & \multirow{2}{*}{**R\({}_{\rm ij}\) (Å)**} & **50** & **100** & **150** & **200** & **250** & **300** \\  & & **TW/cm\({}^{2}\)** & **TW/cm\({}^{2}\)** & **TW/cm\({}^{2}\)** & **TW/cm\({}^{2}\)** & **TW/cm\({}^{2}\)** & **TW/cm\({}^{2}\)** \\ \hline (1, 1)\(\rightarrow\)(1, 2)\(\leftrightarrow\)(2, 1) & 3.80 & 3.43 & 3.19 & 2.94 & 2.82 & 2.82 & 2.70 \\ (1, 1)\(\rightarrow\)(2, 1)\(\leftrightarrow\)(1, 2) & 4.22 & 3.68 & 3.31 & 3.19 & 3.06 & 2.94 & 2.82 \\ (1, 2)\(\rightarrow\)(2, 2)\(\leftrightarrow\)(3, 1) \({}^{*}\) & 4.84 & 3.68 & 3.68 & 3.68 & 3.68 & 3.68 & 3.68 \\ (2, 1)\(\rightarrow\)(2, 2)\(\leftrightarrow\)(3, 1) \({}^{*}\) & 4.55 & 3.68 & 3.68 & 3.68 & 3.68 & 3.68 & 3.68 \\ (2, 2)\(\rightarrow\)(3, 2)\(\leftrightarrow\)(2, 3) & 5.33 & 4.17 & 3.92 & 3.67 & 3.55 & 3.43 & 3.43 \\ (2, 2)\(\rightarrow\)(2, 3)\(\leftrightarrow\)(3, 2) \({}^{*}\) & 4.86 & 3.80 & 3.55 & 3.43 & 3.31 & 3.31 & 3.18 \\ (2, 3)\(\rightarrow\)(3, 3)\(\leftrightarrow\)(4, 2) \({}^{*}\) & 5.49 & 3.80 & 3.80 & 3.80 & 3.80 & 3.80 & 3.80 \\ \hline \hline \end{tabular} \({}^{*}\) Stark shift (\(\varepsilon\)R/2) is not applied to the same charged states IB\({}^{(n+m)+}\) (n = m).  
\end{table} 
Table 3: Calculated R\({}_{\rm cr}\) under various laser intensities.