Visualization of subcycle nonadiabatic-nondipole coupling in strong-field ionization

Light-matter interaction involves the transfer of both energy and linear momentum to matter. In the context of strong-field tunneling ionization, they are manifested as nonadiabatic and nondipole effects, respectively, which have been shown to interact on the subcycle scale. In this work we propose two experimentally feasible protocols for direct visualization of the subcycle interplay between nonadiabatic and nondipole tunneling effects. These protocols hinge on the intersection of the average linear momentum transferred to the released photoelectron at a specific photoemission angle, with the magnitude of this intersection serving as an indicator of the coupling strength. In addition, by defining the instantaneous effective angular frequency of the laser field, we have formulated analytical expressions that provide a quantitative description of the coupling effect. Our results provide a clear and intuitive approach to visualizing the impact of the subcycle nonadiabatic-nondipole coupling effects, thereby enhancing our comprehension of the time-resolved tunneling process through which light imparts both energy and linear momentum to electrons.