Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of
iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is
presented, using femtosecond UV pump pulses and XUV probe pulses from high
harmonic generation. For both molecules the molecular core-to-valence
absorption lines fade immediately, within the pump-probe time-resolution.
Absorption lines converging to the atomic iodine product emerge promptly in
CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π →
σ* excitation in iodobenzene, which is distant from the iodine reporter atom.
We measure a continuous shift in energy of the emerging atomic absorption
lines in CH3I, attributed to relaxation of the excited valence shell. An
independent particle model is used to rationalize the observed experimental
findings
