Effect of orbital symmetry on atomic ionization in near-infrared laser fields

We have performed a comparative study of the photoelectron spectra adopting different initial states (2s or 2p₀) of hydrogen atoms in a near-infrared laser pulse by using the full three-dimensional time-dependent Schrödinger equation. It is demonstrated that the atomic photoelectron spectra oscillate out of step as a function of electron kinetic energies for different initial states (2s or 2p₀), which is well reproduced by the simulations based on strong field approximation, and the above distinct feature is ascribed to the different interferences from the partial electron wave packets detached by positive and negative electric fields for different initial states of 2s and 2p₀.