## 1 Introduction  
Ionization is one of the most fundamental physical processes in the interaction between intense lasers and matter. The ionization process governs many other physical processes, including high harmonic generation, photoelectron holographic imaging, molecular dissociation, electron correlation, etc. [1, 2, 3, 4, 5, 6, 7, 8, 9]. With the development of femtosecond and attosecond laser pulses, scientists now have better knowledge of ionization [10, 11, 12, 13, 14, 15, 16, 17, 18]. The Keldysh parameter value can be utilized to identify the ionization process under various laser conditions [19, 20]. When the Keldysh parameter exceeds one, an electron can absorb multiple photons simultaneously and overcome the ionization potential. When the Keldysh parameter is far less than one, the laser field instead significantly suppresses the Coulomb potential, and electrons escape through tunneling across the potential energy surface.  
Recently, there has been significant interest in multi-electron ionization in a strong laser field. To understand the dynamic processes involved, a variety of theoretical models have been developed. The femtosecond laser field may swiftly remove many electrons with minimum change to the molecule structure. Next, the Coulomb repulsive force affects the charged molecular ions' dissociation, according to the multi-electron dissociative ionization (MEDI) model [21]. In the post-dissociative ionization (PDI) model, reaction products may undergo a second ionization process after dissociation [22]. Conversely, the two-step model proposes that molecule electron loss and, at equilibrium and critical distances, Coulomb explosions (CE) occur twice [23]. [PERSON] et al. put forward a model of charge resonance enhanced ionization (CREI), wherein they showcased the charge resonant states, highlighting a strong correlation with the laser field at a given distance R\({}_{\rm c}\)[24]. Based on this model, all charged molecular ions exhibit an identical energy defect ratio. However, [PERSON] et al. proposed a sequential ionization process for CREI, whereby the electrons are stripped one by one in a laser pulse and nuclear stretching cannot be averted [25]. The energy collected in the previous ionization step is also included in the kinetic energy (KE) that accumulates from each channel. As a result, rather than having a constant value, the R\({}_{\rm c}\) value should fluctuate when the charge states change [26]. Thus, it is important to investigate what causes these dissociation processes, as well as how kinetic energy accumulates in the molecules before dissociation.  
Most studies are mostly focused on homo-nuclear halogen molecules, such as H\({}_{2}\), N\({}_{2}\) and I\({}_{2}\)[26; 27; 28; 29; 30; 31]. The study of the dissociation and ionization process for heteronuclear halogen molecules has been relatively underreported. As a classical heteronuclear halogen molecule, IBr has mostly been studied for the coherent control of the photo-dissociation process [32; 33; 34; 35]. However, we are interested in the intense field dynamic process of IBr. In this paper, we explore the ultrafast dynamics processes of multi-electron ionization and the Coulomb explosion (CE) of IBr in the near-infrared femtosecond laser field. Our results show that high-charged molecular ions are formed when electron ionization is enhanced by increasing nuclear separation. Furthermore, the charge transfer process does not occur in the process and higher-order ionization processes need be considered to achieve higher charge states. This work can provide an understanding of the complex field-induced multi-electron dynamics of heteronuclear diatomic molecules.