Evolution of the transverse photoelectron-momentum distribution for atomic ionization driven by a laser pulse with varying ellipticity

We consider the process of atomic ionization driven by a laser pulse with varying ellipticity. We study the distribution of the momenta of the photoelectrons, ionized by a strong laser field, emitted in the direction perpendicular to the polarization plane (transverse distribution). We show that with changing laser pulse ellipticity, the transverse distribution evolves from the singular cusplike distribution for the close to linear polarization to the smooth Gaussian-like structure for the close to circular polarization. In the latter case, when the ellipticity parameter epsilon -> 1, the strong-field approximation formula for the transverse momentum distribution becomes quantitatively correct.