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.