Concerted elimination of Br2+ resulting from the Coulomb explosion of 1,2-dibromoethane in an intense femtosecond laser field

Concerted elimination pathway leading to Br2+ and C2H4+ from 1,2-dibromoethane molecule has been investigated in 800 nm femtosecond laser field by dc-slice imaging technology. The kinetic energy release and angular distributions of Br2+ and C2H4+ demonstrate that Br2+ results from the two-body Coulomb explosion of the doubly charged parent ion. Ab initio calculations show that the doubly charged precursor overcomes a small energy barrier (0.18 eV) and then dissociates into Br2+ and C2H4+ through a synchronous concerted elimination mechanism. Moreover, the relative yield of the Br2+ channel is obtained, and it remains about 3.4% when the laser intensity exceeds 1.0 × 1014 W/cm2.