Modulation dynamics of atomic Rydberg excitation in strong-field tunneling ionization

Abstract

We theoretically investigate the modulation structures of atomic Rydberg excitation in tunneling ionization and show its various features with diversity of population amplitude as a function of laser peak intensity. Simulating by the time-dependent Schrödinger equation, we find that the distribution of bound states with low-lying principal quantum number n tends to be dominant on total excitation probability with opposite phase compared with other higher n states. At the same time, a well-defined parity angular momentum state makes the main contribution under one certain laser intensity. This Rydberg residual population effect of a rare-gas atom surviving from the laser field is elaborated by the repopulation of Rydberg states via Λ -type Raman transitions joining with a low-energy free electron, which confirms that multiphoton resonance exists in the tunneling regime. It helps in understanding the peak structures of the excited state population quantitatively as well as the atomic stabilization established in the tunneling regime. A physical scenario is also established for the role of Rydberg atom radial size in the ionization.