  We analyze tunnel ionization of a single atom based on the Wigner function
over the classical phase space which inspires improved classical electron
trajectories: these start with exit momenta based on the quantum momentum
function and correspond very well to the subsequent quantum evolution. We
derive an approximate analytic formula to reconstruct the tunnel exit time and
exit momentum from electron momentum data that can be measured e.g. with a
usual time-of-flight electron detector.
