Symmetric Electron Vortices of Hydrogen Ionized by Orthogonal Elliptical Fields

In this paper, we report our numerical investigation on the photoionization of hydrogen by two orthogonal elliptically polarized and time-delayed attosecond pulses; we found that the momentum distributions exhibit a helical structure. The spectral patterns were obtained by making the use of the strong field approximation theory, and analyzed in terms of the irregularity of the overlapped fields. Some morphological characteristics of the generated vortex arms were found to be sensitive to the ellipticity and time delay of the two attosecond pulses. These phenomena could be used to investigate the intrinsic features of the photoionizaiton and complex polarized ultrashort pulses.