Dissociative ionization and Coulomb explosion of ethyl bromide under a near-infrared intense femtosecond laser field

The multi-photon dissociation and Coulomb explosion of ethyl bromide C₂H₅Br under near-infrared (800 nm) femtosecond laser field are experimentally investigated by a DC-sliced ion imaging technique. The sliced images of fragment ions C₂H₅⁺, Br⁺, CH₃⁺, CH₂Br⁺, H₂⁺ and C₂H₃Br⁺ are obtained, and their dissociative pathways are assigned by observing their corresponding kinetic energy release (KER) and angular distribution. It is shown that low-KER components of these fragment ions result from multi-photon dissociation of singly charged parent ion C₂H₅Br⁺, while high-KER components come from Coulomb explosion of doubly charged parent ion C₂H₅Br²⁺. It is also shown that the precursor species [C₂H₅⁺...Br⁺] has a longer lifetime than [C₂H₃Br⁺...H₂⁺] and [CH₃...CH₂Br⁺]. In addition, the probable H₂ and H₂⁺ elimination channels are theoretically simulated by Gaussian 09 software packages, and the results show that the former is an asynchronous process while the latter is a synchronous process.