Photoelectron imaging of 8p Rydberg states of atomic iodine following methyl iodide A-band decomposition

Photoelectron imaging technique has been applied to study (2 + 1) REMPI of atomic iodine through 8p Rydberg states around 253 nm. Full three-dimensional state-specific speed and angular distributions of the photoelectrons were recorded. The branching ratios among the different I⁺ levels revealed that the perturbation on (³P₂)8p series is particularly large among the (³P₂)np series. The violation of core-conserving ionization is attributed to the interactions between the (³P₂)8p and (¹D₂)6p series. The photoelectron angular distributions were found to be well characterized by P₂(cos θ) and P₄(cos θ). A relatively high positive β₂ and a relatively low β₄ observed in (2 + 1) REMPI process indicated that the ionization process can be approximately considered as single-photon ionization via the weakly aligned (³P₂)8p intermediate states.