High-angular-momentum states as population traps in multiphoton ionization

Above-threshold ionization by few-cycle phase jump pulses

We theoretically investigate the above-threshold ionization of hydrogen atoms driven by few-cycle phase jump laser pulses. By numerically solving the three-dimensional time-dependent Schrödinger equation, we demonstrate that the phase jump plays an important role in the ionization process. The cutoff of the photoelectron energy spectrum can extend to a range of very high energy, and the yield of the photoelectrons can be dramatically enhanced by choosing proper phase jump times. Both the classical simulations and Fourier transform method are used to understand the spectra features found in our investigation.