Imprint of transient electron localization in H₂⁺ using circularly-polarized laser pulse

Photoelectron momentum distribution of hydrogen molecular ion in a circularly polarized laser pulse is calculated by solving the three-dimensional time-dependent Schrödinger equation (3D-TDSE). At the intermediate internuclear distance, an unusual multi-peak structure is observed in the angular distribution, which is proved to be a signature of the transient localization of the electron upon alternating nucleus. By tracing the time-dependent ionization rate and bound state populations, we provide a clear evidence that the transient electron localization still exists in circularly polarized pulse and the corresponding multiple ionization bursts are directly mapped onto observable angular distributions. In addition, we introduce an intuitive strong-field approximation model which incorporates laser-induced subcycle internal electron dynamics to isolate the effect of the Coulomb potential of the parent ions. In this way, the timing of each ionization burst can be directly read out from the angular distributions. Our results suggest that the ionization time serves as a sensitive tool encoding intramolecular electron dynamics and can be measured using attoclock technique.