Coulomb explosion and dissociative ionization of 1,2-dibromoethane under an intense femtosecond laser field

Coulomb explosion and dissociative ionization of 1,2-dibromoethane are experimentally investigated in a near-infrared (800 nm) femtosecond laser field by dc-slice imaging technology. The sliced images of the fragment ions C₂H₄Br⁺, Br⁺, C₂H₄⁺, Br₂⁺and CH₂Br⁺are obtained, and their corresponding kinetic energy releases (KERs) and angular distributions are calculated. It is confirmed that the high-KER components come from Coulomb explosion of 1,2-C₂H₄Br₂²⁺, while the low-KER components come from dissociative ionization of 1,2-C₂H₄Br₂⁺. Furthermore, the dissociation pathway leading to C₂H₄⁺and Br₂is theoretically simulated, and the results show that the singly charged precursor overcomes an energy barrier to dissociate via an asynchronous concerted mechanism after undergoing isomerization.