  The intermediate domain of strong-field ionization between the tunneling and
the multiphoton regimes is investigated using the strong field approximation
and the imaginary-time method. An intuitive model for the dynamics is developed
which describes the ionization process within a nonadiabatic tunneling picture
with a coordinate dependent electron energy during the under-the-barrier
motion. The nonadiabatic effects in the elliptically polarized laser field
induce a transversal momentum shift of the tunneled electron wave packet at the
tunnel exit, a delayed appearance in the continuum as well as a shift of the
tunneling exit towards the ionic core. The latter significantly modifies the
Coulomb focusing during the electron excursion in the laser field after exiting
the ionization tunnel. We show that nonadiabatic effects are especially large
when the Coulomb field of the ionic core is taken into account during the
under-the-barrier motion. The simpleman model modified with these nonadiabatic
corrections provides an intuitive background for exact theories and has direct
implications for the calibration of the attoclock technique which is used for
the measurement of the tunneling delay time.
