Time domain study on the tunneling dynamics in photoionization microscopy

The time-dependent wave-packet theory is used to study the tunneling dynamics during photoionization microscopy in a time domain. The results show both the ionized electron current in the time domain and the radial distribution in the spatial domain originate from two contributions: the quantum tunneling ionization of quasi-bound states and the classical above-barrier ionization of continuous states. The two types of ionization exhibit different temporal characters, resulting in a spatial probability distribution which depends on the detection time. For atoms in parallel electric and magnetic fields, the interference narrowing effect is confirmed from two aspects: the linewidth evolution and the electron current distribution. Tunneling ionization reaches its maximum at the point of levels anti-crossing. This makes it possible to observe node structures in the photoionization microscopy of an atom or molecule with strong mixing states. (paper)