Plateau structure in photoelectron spectra of Kr gas induced by intense circularly polarized laser pulses

In the past decade, a large number of investigations of photoionization induced by intense short laser pulses have been carried out. The plateau structure in the photoelectron distribution by intense linearly polarized light was found. This phenomenon is explained by two independent steps. First, an electron tunnels into the continuum state. After that, the electron returns to the core ion, and is rescattered elastically. If the electron is back scattered by the parent ion, the kinetic energy of electron can reach up to 10U_p, where U_p is pondermotive energy. On the other hands, in case of ionization by circular polarization light, plateau structure of photoelectron distribution have been not observed so far. This result is because rescattering process is suppressed in circular polarization light.