电子碰撞诱导苯分子双电离延迟解离同位素效应研究

When molecules lose two electrons upon collisions with electrons, photons, or high-energy ions, the resulting molecular ions undergo direct dissociation or delayed dissociation under the influence of intramolecular Coulomb repulsion. The lifetime of metastable ions in delayed dissociation is crucial for understanding molecular properties and dissociation dynamics. In this study, we performed an experimental investigation on the dissociation dynamics of benzene dications induced by 200 eV electron-impact using a reaction microscope imaging spectrometer. Through ion momentum coincidence measurements, we identified two different dissociation mechanisms for the CH₃⁺ + C₅H₃⁺ and CH₃⁺ + ¹³CC₄H₃⁺ channels: direct dissociation and delayed dissociation. By analyzing the time-of-flight difference between the two fragment ions, we derived the lifetimes of the metastable dications C₆H₆²⁺ and ¹³CC₅H₆²⁺, which were determined to be 1160 ± 34 and 370 ± 28 ns, respectively. The results demonstrate that ¹³C isotopic substitution significantly reduces the lifetime of metastable benzene dications, highlighting the critical role of the isotopic effect in regulating the delayed dissociation dynamics of benzene dications.