XUV multiphoton ionization of molecules is commonly used in free-electron laser experiments to study charge transfer dynamics. However, molecular dissociation and electron dynamics, such as multiple photon absorption, Auger decay, and charge transfer, often happen on competing time scales, and the contributions of individual processes can be difficult to unravel. We experimentally investigate the Coulomb explosion dynamics of methyl iodide upon core–hole ionization of the shallow inner-shell of iodine (4d) and classically simulate the fragmentation by phenomenologically introducing ionization dynamics and charge transfer. Under our experimental conditions with medium fluence and relatively long XUV pulses (∼75fs), we find that fast Auger decay prior to charge transfer significantly contributes to the charging mechanism, leading to a yield enhancement of higher carbon charge states upon molecular dissociation. Furthermore, we argue for the existence of another charging mechanism for the weak fragmentation channels leading to triply charged carbon atoms. This study shows that classical simulations can be a useful tool to guide the quantum mechanical description of the femtosecond dynamics upon multiphoton absorption in molecular systems.

XUV多光子电离分子通常用于自由电子激光实验中，以研究电荷转移动力学。但是，分子解离和电子动力学（例如多光子吸收，俄歇衰变和电荷转移）通常在竞争的时间尺度上发生，并且各个过程的贡献可能难以阐明。我们通过实验研究碘在浅层内壳（4d）上的核-孔电离过程中甲基碘的库仑爆炸动力学，并通过现象学引入电离动力学和电荷转移来经典地模拟碎片化过程。在我们的实验条件下，具有中等通量和相对较长的XUV脉冲（〜75fs），我们发现电荷转移之前的快速俄歇衰变极大地影响了电荷机制，导致分子解离后更高碳电荷态的产量提高。此外，我们认为存在弱电荷碎裂通道的另一种电荷机制，导致碳原子带三重电荷。这项研究表明，经典的模拟可以作为指导分子系统中多光子吸收后飞秒动力学的量子力学描述的有用工具。