TY - JOUR AB - The first hundred attoseconds of the electron dynamics during strong field tunneling ionization are investigated. We quantify theoretically how the electron’s classical trajectories in the continuum emerge from the tunneling process and test the results with those achieved in parallel from attoclock measurements. An especially high sensitivity on the tunneling barrier is accomplished here by comparing the momentum distributions of two atomic species of slightly deviating atomic potentials (argon and krypton) being ionized under absolutely identical conditions with near-infrared laser pulses (1300 nm). The agreement between experiment and theory provides clear evidence for a nonzero tunneling time delay and a nonvanishing longitudinal momentum of the electron at the “tunnel exit.” AU - Camus, Nicolas AU - Yakaboylu, Enderalp AU - Fechner, Lutz AU - Klaiber, Michael AU - Laux, Martin AU - Mi, Yonghao AU - Hatsagortsyan, Karen Z. AU - Pfeifer, Thomas AU - Keitel, Christoph H. AU - Moshammer, Robert ID - 6013 IS - 2 JF - Physical Review Letters SN - 0031-9007 TI - Experimental evidence for quantum tunneling time VL - 119 ER -