Probing time delay of strong-field resonant above-threshold ionization* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11574101, 11674116, 11774111, and 11934006), the Open Fund of Hubei Provincial Key Laboratory of Optical Information and Pattern Recognition (Grant No. 201902), and the International Cooperation Program of Hubei Innovation Fund (Grant No. 2019AHB052).

Abstract

The high-resolution three-dimensional photoelectron momentum distributions via above-threshold ionization (ATI) of Xe atoms are measured in an intense near circularly polarized laser field using velocity map imaging and tomography reconstruction. Compared to the linearly polarized laser field, the employed near circularly polarized laser field imposes a more strict selection rule for the transition via resonant excitation, and therefore we can selectively enhance the resonant ATI through certain atomic Rydberg states. Our results show the self-reference ionization delay, which is determined from the difference between the measured streaking angles for nonadiabatic ATI via the 4f and 5f Rydberg states, is 45.6 as. Our method provides an accessible route to highlight the role of resonant transition between selected states, which will pave the way for fully understanding the ionization dynamics toward manipulating electron motion as well as reaction in an ultrafast time scale.