Helicity-dependent time delays in multiphoton ionization by two-color circularly polarized laser fields

摘要

By numerically solving the three-dimensional time-dependent Schrödinger equation,we have investigated multiphoton ionization of hydrogen atom in the two-color circularly polarized(TCCP)laser fields consisting of a strong 400 nm and a much weaker 800 nm pulses.Due to the presence of perturbative 800 nm laser pulse,sideband peaks emerge between the above-threshold ionization rings in the photoelectron momentum distributions.Our numerical results show that the sideband peaks exhibit one-lobe structure in the co-rotating TCCP laser fields,while it displays the three-lobe structure in the counter-rotating TCCP laser fields.Moreover,the photoelectron yield of sidebands in the co-rotating TCCP fields is much higher than those of the counter-rotating TCCP fields.These phenomena could be well explained from the perspective of the photon-absorption channels via the selection rules.Interestingly,an obvious phase shift between the sidebands of different orders from the co-rotating and counter-rotating TCCP fields is observed.This shift indicates the helicity-dependent time delay in the one-photon continuum-continuum transition process.