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+, Br-2(+) 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 Br-2 is 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.