Wigner versus Stark: Connecting quantum to classical in a tunnel ionization process

We present a framework designed to illustrate the dynamics of a quantum particle tunneling from a bound state into a continuum of states under the influence of an external field. We concentrate on the question of what is the best classical-level description of the escaping particle. A toy model is constructed and investigated through complementary numerical, analytical, and approximate solutions. Issues related to the location of the apparent exit from the “quantum tunnel” are addressed in the language of Wigner trajectories and discussed in relation to the other types of solutions.