Ultrafast nonadiabatic nuclear dynamics on excited electronic states of iodobenzene

In this study, we calculate the dynamics associated with C-I bond dissociation in Iodobenzene (C₆H₅I) after a 266 nm pump pulse. We compare our calculations with an experimental ultrafast electron diffraction (UED) probe [1,2]. This approach uncovers two distinct bond dissociation times in Iodobenzene. To interpret these differences, we conduct SHARC[3] molecular dynamics calculations to simulate the differing molecular trajectories. Importantly, spin-orbit effects and electron correlation must be considered. Our findings show two dissociation rates, qualitatively consistent with experimental observations, irrespective of the initial state of the molecule. We observe that slower dissociation trajectories transition to a specific singlet state, unlike the faster dissociation trajectories. The rapid dissociation is linked to vibrational modes that cause significant fluctuations of the C-I bond along its axis, facilitating swift dissociation. This research not only advances our understanding of bond dissociation in photoexcited molecules but also offers insights into the complex dynamics of similar molecular systems.

[1] M. Centurion, Journal of Physics B 49 062002 (2016)

[2] M. Centurion et.al., Annu. Rev. Phys. Chem. 74 21-42 (2022)

[3] S. Mai et.al., WIREs Comput. Mol. Sci. 8 1370 (2018)