Asymmetry of the photoionization rate of H atoms by a sequence of one-cycle laser pulses

Using an unperturbated scattering theory, the characteristics of H atom photoionization are studied respectively by a linearly and by a circularly polarized one-cycle laser pulse sequence. The asymmetries for photoelectrons in two directions opposite to each other are investigated. It is found that the asymmetry degree varies with the carrier-envelope (CE) phase, laser intensity, as well as the kinetic energy of photoelectrons. For the linear polarization, the maximal ionization rate varies with the CE phase, and the asymmetry degree varies with the CE phase in a sine-like pattern. For the circular polarizaion, the maximal ionization rate keeps constant for various CE phases, but the variation of asymmetry degree is still in a sine-like variation pattern.