Resolving distinct ionization channels via interferometric phase analysis of partial waves

We extend the interferometric method to multiphoton ionization, aiming to disentangle different ionization channels simultaneously for resonance-enhanced multiphoton ionization by numerically solving the time-dependent Schr"odinger equation. The approach is based on the interference of the bichromatic ionization using an $\ensuremath{\omega}\text{\ensuremath{-}}4\ensuremath{\omega}$ pulse pair. By tuning the relative phase of the two-color laser pulse, we can extract the partial-wave complex amplitudes from the photoelectron angular distributions. Our analysis shows that controlling the fundamental frequency of the bichromatic pulses enables us to resolve resonant and nonresonant channels simultaneously. Taking the hydrogen atom as the prototype, at the resonant frequency, while the $g$ partial wave is resonance-free, the quantum phases of the $s$ and $d$ partial waves and the corresponding Wigner time delays are significantly influenced by the intermediate resonance. Given that the above pulses are now accessible through high-harmonic sources or free-electron lasers, such investigations could disentangle the ionization channels of more complex targets.