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 $\epsilon \to 1$, the strong-field approximation formula for the transverse momentum distribution becomes quantitatively correct.

Figure 1

(top) Distribution $W\left(p_{\perp }\right)$ for $\epsilon =0$ (solid red line), $\epsilon =0.2$ (long-dashed green line), $\epsilon =0.4$ (short-dashed blue line), and $\epsilon =0.5$ (dotted magenta line). (bottom) Distribution $W\left(p_{\perp }\right)$ for $\epsilon =0.6$ (solid red line), $\epsilon =0.7$ (long-dashed green line), $\epsilon =0.8$ (short-dashed blue line), and $\epsilon =1$ (dotted magenta line). Pulse parameters are $E=0.0534$ a.u., $\omega =0.057$ a.u., and a pulse duration of four optical cycles.

Figure 2

Function $V\left(p_{\perp }\right)=lnW\left(p_{\perp }\right)$ (red solid line) and results of the fit based on Eq. (8) for $\epsilon =0,0.4,0.6,1$ (left to right, top to bottom). Pulse parameters are $E=0.0534$ a.u., $\omega =0.057$ a.u., and a pulse duration of four optical cycles.

Figure 3

Function $V\left(p_{\perp }\right)=lnW\left(p_{\perp }\right)$ (red solid line) and results of the fit based on Eq. (8) for $\epsilon =0,0.4,0.6,1$ (left to right, top to bottom). Pulse parameters are $E=0.0534$ a.u., $\omega =0.057$ a.u., and a pulse duration of ten optical cycles.

Figure 4

Fitting parameters $A$ and $\alpha$ in Eq. (8) as functions of the ellipticity parameter $\epsilon$. The pulse duration is four optical cycles (red solid line) and ten optical cycles (green dashed line). Other pulse parameters are $E=0.0534$ a.u., $\omega =0.057$ a.u.

Figure 5

Angular momentum distributions for (left) $\epsilon =0$ and (right) $\epsilon =0.8$. Pulse parameters are $E=0.0534$ a.u., $\omega =0.057$ a.u., and a pulse duration of four optical cycles.

Figure 6

Distribution $W\left(p_{\perp }\right)$. Projection on the Coulomb scattering states with $L_{\min }=0$ (solid red line), $L_{\min }=5$ (long-dashed green line), $L_{\min }=10$ (short-dashed blue line). The distribution for $L_{\min }=10$ is scaled by a factor of 10 for better visibility. Pulse parameters are $\epsilon =0$, $E=0.0534$ a.u., $\omega =0.057$ a.u., and a pulse duration of four optical cycles.