Delayed Dissociation and Transient Isomerization during the Ultrafast Photodissociation of the Tribromomethane Cation

J Phys Chem Lett. 2024 Dec 2:12188-12196. doi: 10.1021/acs.jpclett.4c02838. Online ahead of print.

Abstract

We present a time-resolved measurement of the photodissociation and photoisomerization dynamics of bromoform (CHBr3) in the mono- and di-cationic states produced by near-infrared (NIR) strong-field ionization. The dissociation process is probed by NIR-induced Coulomb explosion imaging. We find that for dissociation channels involving production of HBr and Br2 fragments, which require the formation of new bonds, the dissociation appears to be delayed with respect to the primary C-Br bond dissociation channel. Ab initio molecular dynamics simulations support the observed delay. Moreover, the simulations suggest that reaction pathways involving transient isomerization via H- and Br-migration in the CHBr3 monocation are responsible for the formation of the HBr and Br2 fragments.