Role of the Coulomb potential on the ellipticity in atomic high-order   harmonics generation
  The role of the Coulomb potential on the generation of elliptically polarized high-order harmonics from atoms driven by elliptically polarized laser is investigated analytically. It is found that the Coulomb effect makes a contribution to the harmonic ellipticity for low harmonic orders and short quantum path. By using the strong-field eikonal-Volkov approximation, we analyze the influence of the Coulomb potential on the dynamics of the continuum state and find that the obtained harmonic ellipticity in our simulation originates from the break of symmetry of the continuum state. 
Xiaosong Zhu, Meiyan Qin, Qingbin Zhang, Weiyi Hong, Zhizhan Xu, and   Peixiang Lu
physics.atom-ph physics.optics