Fig. 1: A schematic representation for the photodynamics of BiI₃ in acetonitrile.

Upon 400 nm excitation, BiI₃ in acetonitrile solution undergoes isomerization to form iso-BiI₂-I and dissociation to form BiI₂• and I• radicals. The kinetics and structural movements at the initial stage of those reactions were investigated in this study. Here, we answer the following three questions using fs-TRXL; (i) roaming-mediated direct isomerization or cage-induced isomerization, (ii) wavepacket trajectory for the isomerization, and (iii) wavepacket trajectory of the dissociation fragments. Qualitative potential energy surfaces are shown along the Bi···I distance (R_Bi···I) and Bi-I-I angle (θ_Bi-I-I). Green and magenta spheres represent the Bi and I atoms, respectively. The solvent cage surrounding the solute molecules is represented by gray spheres. Possible wavepacket trajectories are represented with colored arrows. The blue, red, and green arrows represent the wavepacket trajectories for the dissociation, roaming-mediated direct isomerization, and cage-induced isomerization.