Photodissociation dynamics of organic iodides studied via ultrafast photoelectron spectroscopy*

Photodissociation reactions are prototypical systems for ultrafast dynamics studies. While direct excitation to a repulsive excited state followed by direct dissociation is the fastest dissociation mechanism, bond breaking can occur via a variety of pathways. In the present study, we use ultrafast photoelectron spectroscopy with resonant ionization via molecular Rydberg states to investigate C-I bond cleavage in the molecule 1,4-diiodobenzene excited by 4.6 eV photons. The photoelectron spectrum suggests that the first step of the dissociation is an ultrafast curve crossing from the initially excited bound state. Subsequent probing via resonant ionization reveals a detailed picture of the ensuing wavepacket dynamics.