  We investigate the physical processes in which an electron, upon return to
its parent ion, promotes a second electron to an excited state, from which it
subsequently tunnels. Employing the strong-field approximation and saddle-point
methods, we perform a detailed analysis of the dynamics of the two electrons,
in terms of quantum orbits, and delimit constraints for their momentum
components parallel to the laser-field polarization. The kinetic energy of the
first electron, upon return, exhibits a cutoff slightly lower than $10U_p$,
where $U_p$ is the ponderomotive energy, as in rescattered above-threshold
ionization (ATI). The second electron leaves the excited state in a direct
ATI-like process, with the maximal energy of $2U_p$. We also compute
electron-momentum distributions, whose maxima agree with our estimates and with
other methods.
